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Coastal Zone Center 4OSA OE~ 14 977 INFO �AD:CETER Redu~Ing flomldWImgethog buildindsign:a guidenmanual. Federal Insurance Administration (j) ~~~~National Flood Insurance Program Department of Housing and Urban Development ~TC- ~ U5 '-' 197 U. S. DEPARTMENT OF COMMERCE NOAA COASTAL SERVICES CENTER 2234 SOUTH HOBSON AVENUE CHARLESTON, SC 29405-2413 ELEVATED Id 0 "- rs RESIDENTIA STRUCTURE a La I-' m6 contents: ELEVATED RESIDENTIAL FOUNDATIONS Reducing Flood Damage Through Building Design: A Guide Manual FOREWORD iii INTRODUCTION v Floods-The Recurring Menace vii The National Flood Insurance Program viii The Emergency Program viii The Regular Program ix Flood Plain Management ix Conditional Federal Funding x Prudent Use of the Flood Plain x United States Flood Map xi Part One: ELEVATED RESIDENTIAL STRUCTURES 1-1 Elevated Residential Structures: Restrictions and Considerations 1-3 Site Selection 1-4 Design 1-4 Engineering Factors 1-4 Building Materials 1-5 Utilities 1-5 Techniques for Elevating Residences 1-6 Methods of Elevating Structures 1-6 Posts 1-6 Piles 1-6 Piers 1-6 Walls 1-7 Pedestals 1-7 Representative Elevated&Structures 1-8 Wood Posts 1-8 Steel Posts 1-11 Wood Piles 1-12 Concrete and Masonry Piers 1-14 Walls 1-17 Earth Fill 1-18 PAGE Part Two: DESIGNING ELEVATED FOUNDATIONS 2-1 Designing Elevated Foundations: Introduction 2-3 Guidelines and Performance Criteria 2-4 Design and Construction Guidelines 2-5 Design and Construction Factors 2-5 Post and Pile Foundations 2-12 Piers 2-20 Performance Requirements and Criteria 2-26 Definitions 2-26 Performance Requirements and Criteria for Residential Structures in Flood HazardAreas 2-28 Performance Requirements-A: Unacceptable Risks 2-29 Performance Requirements--B: Unacceptable Health Hazards 2-31 Performance Requirements-C: Damage of Unacceptable Magnitude 2-32 Part Three: A BRIEF SURVEY OF DESIGN IMPROVEMENTS 3-1 Introduction 3-3 Northeastern U.S. 3-4 Bridgeport, Connecticut 3-4 Charlestown and Newport, Rhode Island 3-8 Southern U.S. 3-12 New Orleans, Louisiana 3-12 Midwestern U.S. 3-14 Chicago, Illinois 3-14 Western U.S. 3-16 San Francisco, California 3-16 Part Four: COST ANALYSIS OF ELEVATED FOUNDATIONS 4-1 Cost Analysis 4-3 Cost Analysis Approach 4-3 Cost Comparison Considerations 4-5 The Real Cost of Elevating a Residence 4-6 Estimating Elevated Foundation Costs 4-8 Elevation Cost Differences 4-8 Slab-on-Grade vs. Elevated Foundations 4-10 Crawl Space vs. Elevated Foundations 4-12 Basement Construction vs. Elevated Foundations 4-14 Future Factor 4-15 Local Estimating Guidelines 4-15 Estimating Forms 4-17 Slab-on-Grade 4-19 Crawl Space 4-20 Basement 4-21 Wood Post 4-22 Wood Pile 4-23 Concrete Pier 4-24 APPENDIX 5-1 Local Sources for Flood Data 5-3 Glossary 5-10 Annotated Bibliography 5-15 Acknowledgements 5-19 FOREWORD This manual is intended for use by designers, home builders, community leaders, local officials, and home owners who wish to build prudently in areas of special flood hazard and to meet the requirements of the National Flood Insurance Program. A key provision of that program, which is administered by the Federal Insurance Administration (FIA) of the Department of Housing and Urban Development (HUD) calls for wise use of flood plains through the adoption of appropriate flood plain management regulations by local communities. To reduce losses from flooding, one of these appropriate regulations requires all living areas of residences built within the flood plain area (as well as housing substantially rebuilt or improved) to be at or above the base flood level as indicated on FIA's Flood Insurance Rate Map. This manual provides background information on the National Flood Insurance Program, and the hazards associated with building in the flood plain, a review of existing alternative approaches for housing built on raised foundations, recom- mended performance criteria for the construction of foundation systems in flood hazard areas and some indications of design solutions. It is not the intent of this manual to encourage building in flood plains, but rather when such building does or must occur, this manual seeks to provide information which, if effectively and appropriately used, will reduce flood losses. These examples, guidance, and explanations in this manual reflect information currently available to the Federal Insurance Administration on residential construction subject to flood hazards. To ensure compliance with Federal requirements, readers are urged to consult pertinent regulations promulgated by FIA together with local codes, ordinances and other regulatory measures that may be in effect for more complete information. In order to keep you up to date on new developments in this area, the Federal Insurance Administration may modify the provisions of this manual in the future as new information becomes available, or as the provisions of the program change. Therefore, we welcome any comments, suggested improvements, or additional information that you may wish to submit. -Rbert Hunter Acting Federal Insurance Administrator Department of Housing and Urban Development 451 Seventh Street, S.W. Washington, D.C. 20410 A Introducton INTRODUCTION: FLOODS-THE RECURRING MENACE Our country has been blessed with abundant water resources which we have been able to use to make its land fruitful, to generate power to light our cities and fuel our industry, and to utilize for the recreation of our people. Yet, as we know that water is life-sustaining and enhancing, we have learned that its destructive potential is enormous and tragic. For flooding is a part of the natural hydrologic cycle of the earth. Driving rains can transform rivers and streams into swollen menaces to both life and property. Violent winds can whip oceans and lakes into furies which devastate the shoreline. A torrential downpour or even a steady prolonged drizzle can turn hillsides and slopes into rivers of mud that can either foul our homes and businesses or literally carry them off. While parts of the State of California Part of the explanation for this mounting loss are the areas most often associated with this of property is that improper and unsafe devel- hazard they are by no means the only areas of opment in flood hazard areas has accelerated the country to experience such problems. beyond the point that flood protection is feasible. Often flood control systems have Floods have been a fact of life for Americans proved to be counter-productive becausethey since the first human settlements on this have resulted in an increase in losses due to continent. As early as the sixteenth century flooding. While they are engineered to protect Spanish explorers encountered Indian villages known flood hazard areas up tc a certain limit, in the Mississippi Valley where the rough-hewn their presence has most often encouraged a houses were constructed above the ground false sense of security that has led to additional level to protect them from flooding. In our development of flood hazard areas beyond that recorded history, there have been more than limit of protection. Flood prone communities 10,000 documented floods in our country, and across the country have learned the bitter countless others went unrecorded in areas we lesson that flood protection systems alone are had yet to occupy. not the answer to their community's flood problem, and many times contribute to it. We know from experience that floods and flood-related damage from erosion or Especially in the last decade, Americans have mudslides are a major threat to the security and moved at an increasing rate to coastal and well-being of our people. Fully 90% of the riverine locations which had previously been damage caused by natural disasters in this avoided. Popular because they are picturesque, country is caused by floods despite the efforts they have been merchandised as desirable we have made at flood control. Since 1925 it is locations to live, work, retire. Nevertheless, the estimated that more than $9 billion tax dollars fact remains that many scenic locations are have been spent on flood protection systems hazardous because they are part of the flood such as dikes, dams, and levees. Yet the plains-the area intended by nature to average annual loss from floods in recent years accommodate the discharge and overflow of has been $1.5 billion; and by the year 2020, it is its water ways. When you occupy the flood predicted it would reach $5 billion per year if plain, you run the risk that a body of water will development continued to expand in flood reclaim its right of passage and be very costly prone areas in the same manner as in the past. in terms of human life and property investment. vii THE NATIONAL FLOOD INSURANCE The National Flood Insurance Program is PROGRAM administered in two phases: the Emergency Program and the Regular Program. Because that is a price we cannot afford, the National Flood Insurance Program was initiated by the Congress in 1968. Broadened and strengthened by amendments in 1969, 1971, and 1973, the National Flood Insurance Program is designed tofulfill one essential pur- pose: flood hazard mitigation through reducing the amount of property exposed to damage from flooding. The program is administered by the Federal Insurance Administration (FIA) in the Department of Housing and Urban Development(HUD) and its scope includes all communities identified by FIA as containing flood hazard areas. To date, more than 17,500 communities have been so identified, of the approximately 22,000 estimated to contain such areas. The National Flood Insurance Program is based THE EMERGENCY PROGRAM on a dual principle: to make flood insurance available to property owners in flood prone The function of the Emergency Program is to areas; and to require sound practices of flood make flood insurance readily available to plain management in flood-prone communities. property owners throughout flood-prone communities. The operation of the program is The program offers the first affordable flood simple and direct. The FIA notifies a insurance protection for all buildings and their community it has been identified as contents located throughout an entire flood-prone by providing the community with a community as long as the community elects to Flood Hazard Boundary Map. Prepared from the participate in the program. This special best available data, this map is a preliminary federally subsidized insurance coverage for delineation of special flood-hazard areas within flood losses is made available through local the community with a definite likelihood of agents under an operating agreement between inundation. A community receiving such a map HUD and the National Flood Insurers Associa- must then either make application to partici- tion, a pool of 133 private insurance pate in the program or submit data to FIA companies. supporting that it no longer is subject to flooding. In return for the Federal subsidy, the program requires affected communities to prudently Once a community receives notification from regulate new construction and development in FIA that it is flood-prone, accompanied by a special flood hazard areas including all land Flood Hazard Boundary Map, it has one year to inundated by flooding up to the level of the qualify for the program. The application flood which has a 1 % chance of being equalled procedure requires communities to regulate or exceeded in any given year. This level is future development in special flood-hazard known as the "base flood" or "1 00-year flood" areas as well as to provide FIA with certain rele- and is used by virtually every Federal agency in vant information. When the application is the administration of their programs as they complete and forwarded to FIA, it is normally relate to flood plains. In addition, this same processed within less than two weeks and, if no standard is required, either by law or further information is required, the community regulation, in many states and is used admin- is admitted into the Emergency Program. As istratively in the operations of virtually every soon as that occurs, limited amounts of state's programs dealing with the use of flood federally subsidized insurance become plains. available in that community. viii The limits of coverage for the initial or first available, but at actuarial rates. Second, layer insurance protection available under the actuarial rates are charged for the additional or Emergency Program are up to $35,000 for second layer coverage to existing structures single-family structures and up to $100,000 for and for all coverage for new structures. New all other residential and non-residential construction is that which is started after the structures. Contents coverage may be effective date of the community's FIRM or purchased up to $10,000 per unit in residential December 31, 1974, whichever is later. and up to $100,000 in non-residential structures. THE REGULAR PROGRAM Once a community has qualified for the Emergency Phase of the National Flood Insurance Program and subsidized insurance protection is available, anextensive technical Flood Insurance Study of the community's flood-hazard areas is conducted by an engineering contractor for the Federal Insurance Administration in preparation for entering the Regular Program. This detailed - ' ; l study includes development of a Flood Milan~I Insurance Rate Map and is conducted at no cost to the community. The flood elevations derived from this study and the Flood Insurance Rate Map are the basis on which the actuarial (non-subsidized) insurance rates for the community are established and specific flood plain management regulations formulated. As soon as this information is assembled, the FIA publishes notice of tentative base flood elevations twice in a local newspaper and once in the Federal Register. The community has the FLOOD PLAIN MANAGEMENT right to appeal these elevations to the FIA. After any appeals are resolved they become of- The specific flood plain management ficial base flood elevations for the community. regulations that must be adopted depend to some degree upon the data developed in the The final determination of flood elevations and detailed insurance study and provided to the the Flood Insurance Rate Map has two community by FIA. Therefore, these important effects: First, once a community's .regulations may be adopted incrementally by flood elevations are finalized, a six-month the community as the necessary data becomes period begins during which the community available. For example, throughout the must adopt additional flood plain management Emergency Program the community is required regulations. After adopting these regulations to apply minimal flood plain management regu- by the end of this period or at any time before lations based on the Flood Hazard Boundary that, if the community elects to do so, the Map and is required to reasonably utilize any community enters the Regular Program and additional data that may be available from other additional flood insurance coverage becomes sources to establish the flood elevations. ix However, after the base flood elevations and and Small Business Administration, but also Flood Insurance Rate Map are available from money provided through federally regulated, FIA, the community must adopt regulations supervised or insured financial institutions which will protect from inundation any new such as banks, credit unions and savings and construction that may take place in its special loan associations. Therefore, the availability of flood-hazard areas up to the magnitude of the conventional mortgage financing for structures base flood. Finally, FIA will provide the riverine in the special flood-hazard areas of flood-prone flood-prone community with data necessary to communities is conditional upon participation establish its floodways. In the case of coastal in this program. communities, FIA will provide maps designating coastal high hazard areas for which additional regulations must be adopted to PRUDENT USE OF THE FLOOD PLAIN protect new construction and substantial improvement of existing structures. A riverine The purpose of these regulations and community must designate its own floodway requirements is not to prohibit development in on an official map and then adopt additional the flood plain but rather to encourage the most regulatory measures to protect against appropriate use of flood-prone areas. The encroachments on these areas which would long-term benefit of the National Flood Insur- Interfere with the discharge of flood waters. ance Program will be the prudent use of our land resources in flood-prone areas to protect Once flood plain management regulations have individuals and communities from devastating been adopted, they must be enforced. If they flood losses. For example, lowlands stretching are permitted to lapse or are inadequately en- along the banks of a river or stream subject to forced the community will be subject to flooding may be unsuitable for high density suspension from the program. development, but may be ideal locations for agricultural uses, parks, golf courses, or other open space purposes. CONDITIONAL FEDERAL FUNDING The essential risk of urban development of the flood plain is that it will, intime, reduce the The incentive to participate in the National flood water storage area and the permeable Flood Insurance Program is more than just the land surface available to absorb flood water and availability of affordable flood insurance pro- block the flow of floodwaters, thus, exposing tection. In order to achieve the goal of additional lives and property to the possibility mitigating flood disasters, the Congress of flooding and, thereby, increase the social legislated in the Flood Disaster Protection Act and economic costs of paying for flood of 1973 that nearly all forms of Federal or damage. By controlling development in these federally related financial assistance for the areas so that the uses are appropriate to the acquisition or construction of buildings in the hazard, the potential for public and private loss identified flood-hazard areas of flood-prone can be greatly minimized. communities will be conditional upon: 1. Community participation in the program; and 2. The purchase of flood insurance in con- junction with that assistance. The Act defi nes Federal or federally related financial assistance to include not only loans and grants from Federal agencies such as Veterans Administration, Federal Housing Administration, U.S. Department of Agriculture x UNITED STATES FLOOD MAP* Water Resources Council $24.2 M~~~~~~~~~., ;218.0 X < $125.9 |24-) 6 ee $19.0 ESTIMATED ANNUAL FLOOD DAMAGE - 1980 (In millions of dollars) Unless flood plain management and building practices are significantly improved by the year 1980, the potential flood damage may exceed 2.5 billion annually. Elevated Residential Structures V~~- 1 I ---IN=OE ELEVATED RESIDENTIAL STRUCTURES: These requirements come into effect the RESTRICTIONS AND CONSIDERATIONS moment a community enters the Emergency Program. When the detailed flood insurance In order to participate in the National Flood study of the community has been completed Insurance Program a community must agree to and the base flood elevations determined, the require building permits for all proposed con- community must adopt these additional struction or other improvements in the Special minimal regulations. Flood Hazard Area (SFHA) of the community and to review building permit applications in *For residential structures within the area that area to determine whether the proposed of special flood hazards, the community building sites will be reasonably safe from m ust req u ire new construct ion and sub- flooding. stantial improvements to existing struc- tures to have the lowest floor (including Building permits are required only in the the basement) elevated to or above the identified flood-prone portion of the level of the base flood. community-if a map designating these areas has been issued by the FIA. However, if no map *Where the threat of river flooding exists, has been issued, building permits are required the community must insure that until a for the entire community. Other requirements floodway has been designated, no use- include that if a proposed building site is in a including land fill-will be permitted with- location that has a flood hazard, the community in the flood plain area having special flood must require that the proposed new hazards unless it can be demonstrated that construction or substantial improvement of the proposed use, when combined with all existing buildings (including mobile homes) be other existing and anticipated uses, will designed and anchored to prevent flotation, not increase the water surface elevation of collapse, or lateral movement of the structure. the base flood more than one foot at any It must require, as well, the use of construction point. methods and practices that will minimize flood damage and the use of construction materials and utility equipment that are resistant to flood The reason for these minimum regulations and damage. construction standards is clear. Building houses in flood-hazard areas is risky. The risk Moreover, the community must review is not only to the occupants, to the building subdivision proposals and other proposed new and its contents, but also to the utilities and developments to make sure they are consistent other service systems vital to them. The follow- with the need to minimize flood damage. New i ng specif ic considerations will hel p to public utilities and facilities such as sewer, minimize flood damage. gas, electrical and water systems must be A ~located and constructed to minimize or eliminate f lood damage and adequate drainage must be provided to reduce the exposure of the development to flood hazards. Finally, the community must require that any new or replacement water supply systems and /or sanitary sewage systems be designed to minimize or eliminate inf iltration of flood waters into the systems and discharges from these systems into flood waters. Any new or replacement on-site waste disposal systems must be located so as to avoid its impairment or contamination from f looding. 1-3 SITE SELECTION DESIGN Whenever possible, avoid encroachment on the Design considerations are important not only in flood plain. If, in buying a lot or selecting a site terms of protection from flooding, but also in for development, encroachment on the flood terms of constructing an aesthetically plain cannot be avoided, recognize that the risk appealing residence that is compatible viith its and severity of flooding generally decrease with community. The types of interference or the distance from the river channel or from damage houses may suffer under flood coastal waters. However, this may not always conditions should be anticipated and designed be the case, so it is important to check the level for to provide safe living accommodations. At of the base flood in relation to the proposed the same time, well-designed elevated site. If the base flood level has not been de- residences should provide a smooth transition termined, it would be wise to consult local from ground to dwelling, the foundation being flood history data before making a final' site integrated with or complementing the structure selection. The essential objective in a river itself. Creative landscaping using trees, flooding situation at a minimum is to locate in shrubs, and fences can enhance the the flood fringe, in that area beyond that which appearance of elevated structures by softening is needed to carry off the waters of the base the effect of potentially harsh or barren ex- flood, posures. In the case of subdivisions or de- velopments, the design quality of an elevated The regulations of the National Flood Insurance home will be enhanced if the surrounding Program specifically prohibit building and/or neighborhood and community have been landfill in a floodway, if such has been designed to accommodate elevated homes. designated, if the results would obstruct the flow of flood waters and, therefore, increase flood heights. Similarly, building in a coastal high hazard area is also not permitted unless the site is landward of the mean high tide level and the lowest floor is elevated to the level of the base flood on adequately anchored piles. The space below the lowest floor must be kept open and free of obstruction. The lowest structural members of the floor system of a new building in this area, or any part of the outside wall, should be above the base flood elevation. Development should also be diverted away from identified mudslide or erosion prone areas. Only where site and soil investigation and proposed construction standards assure complete safety for future residents should such sites be considered. ENGINEERING FACTORS Overall, customary site selection criteria must be utilized to evaluate the suitability of a site. The most important engineering consideratior Drainage, height of the water table, soil and is to design an elevated foundation to resist thl, rock formations, topography, water supply and forces caused by the base flood and the sewage disposal capability should be con- character of its flood waters. A static flood is sidered along with economic and planning characterized by slow-moving, slow-rising criteria, such as cost, access, and compatible water. This occurs most typically in the riverine land use. floodway fringe or backwater coastal situation. 1-4 Foundations built in these areas must first An attempt should be made to minimize losses elevate the building above the level of the base both below and above the level of the base flood, and second, be able to withstand the flood. This can be accomplished by selecting hydrostatic loads placed upon the foundations. building materials and furnishings (such as Velocity floods are characterized by rapidly floor coverings) that are resistant to inundation moving and surging water. This condition is and by designing and engineering buildings in typical in exposed coastal and riverine flash a manner that will allow them to dry out flood areas. In this situation, elevated founda- quickly. A discussion of building materials can tions must not only raise the structure above be found in the Corps of Engineers' publication the base flood waters and withstand the No. Ep 1165 2 314, Flood-Proofing Regulations. hydrodynamic forces of flowing water, but it must also resist the impact of water-borne debris and the scouring effects of wave and UTILITIES tidal action. The foundation should also be constructed so as to offer the minimum Elevating a residential structure above the base possible resistance to flow in order to reduce flood level will provide added physical safety to the dynamic forces without reducing the the occupants and will lessen the possibility of structural strength of the foundation. (A further flood damage to the structure and its contents. discussion of these situations follows in However, interruption of utility services because Section 2 of this manual.) In coastal of flood damage may render the residence high hazard areas (CHHA) the lowest structural uninhabitable during flood and post-flood member of the floor system should be above recovery periods. the base flood level. Elevated structures, therefore, should be serviced by mechanical equipment that is also elevated or flood proofed above the base flood, and by utility systems that are designed to minimize or resist flood damage and infiltration. Owners, builders, developers, and communities that have no alternative but to construct in a flood-hazard area should anticipate utility disruptions and seek comprehensive engineering data and profes- sional guidance to prevent and minimize them. BUILDING MATERIALS Replacement of water-damaged building materials and repair of structural damage re- sulting from material failures are major cost components of flood damage. The base flood level is a selected flood design criteria which is actually a compromise between extreme, catastrophic flooding and more regular or even annual riverbank and coastal shoreline flooding. Obviously, floodwaters can and will exceed the level of the base flood, and thus, even residences elevated to the level of that flood will be subject to possible water damage from a greater flood. : 1-5 TECHNIQUES FOR ELEVATING RESIDENCES METHODS OF ELEVATING STRUCTURES PILES Two general methods are available to raise the Similar to posts, piles are long, slender shafts lowest floor of a residence to or above the base of wood, steel, or reinforced concrete driven flood level. One of these requires filling the into the earth to support a horizontal load. The low-lying area with compacted soil, then load-bearing capacity of each pile is building in the conventional manner. The other determined by the frictional resistance between method requires construction of an elevated the soil and the pile surface and/or by the end foundation to raise the lowest floor of the bearing of the pile. Piles should be driven to a residence above the base flood level. This designed depth, depending on their use, or to manual considers five methods of constructing refusal. Again, soil type and anticipated scour elevated foundations: Posts, Piles, Piers, are important considerations. Walls, and Pedestals. Each of these methods is reviewed on the following pages and pictorially As in post construction, piles may be cut off or presented in the section entitled Representative extended to a building's roof line. Piles Elevated Residences. extended to the roof line, however, present alignment problems, which could add to the cost of construction. The majority of pile POSTS houses built for flood and less demanding conditions utilize wood piles. The strength and Wood posts and steel columns are sometimes scour resistance of pile construction makes it used in elevated construction. The posts or especially suitable for buildings in coastal and columns are placed in either machine drilled or other areas where high-water velocity and surge hand dug holes and may be secured in the conditions are common. ground on concrete footings or held in place by either embedment in the ground and/or poured-in-place concrete. The depth of PIERS embedment necessary to firmly secure the post depends on the type of soil in which it is Piers are vertical supports usually made of rein- placed, its condition and the anticipated scour. forced concrete or reinforced masonry (brick or concrete block). Essentially, they are heavy Posts can either extend from grade to or slight- columns set on footings appropriate for the soil ly above the base flood level where the first conditions and spaced to accommodate the floor deck is constructed, or they may extend floor framing and loads. They also may be con- through the deck to the roof. Posts extended in structed without footings by augering or the latter manner are a means of tying a digging holes and then casting reinforced structure together to increase wind or lateral concrete piers in place. The use of this method resistance. The majority of elevated residences depends on whether the soil is capable of de- utilizing post construction use wood posts. veloping adequate end bearing. 1-6 WALLS they will not float away and add to the floating debris which may destroy other structures. Any Elevating residences on walls is a relatively materials resistant to water damage, such as simple and effective means of providing flood concrete block, can be used in construction of protection. This approach simply requires that wallIs for elevated structures. the first habitable floor of a residence be built on foundation walls that extend above grade to PEDESTALS t'he level of the base flood or h igher. The last and least often used method of It is important the foundation walls be arranged elevating structures is pedestal construction. A to provide open spaces through which water pedestal is a single structural unit that can flow to equalize pressure. In velocity flood supports a canti levered floor deck at or above * ~~~situations, it is important that the foundation the level of the base flood. Most frequently it is walls be parallel to the flow of the f lood waters. constructed of reinforced concrete or reinforced masonry and set on a spread * ~~~If infill walls are used they should be of a footing. knockout variety to prevent the accumulation of debris and thus the potential destruction of the Currently pedestal construction is not a foundation from flood waters. The knockout common type of elevated foundation, primarily walls should be designed or anchored so that due to higher construction costs. 1-7 REPRESENTATIVE ELEVATED STRUCTURES WOOD POSTS POSTS TERMINATED AT __ ~~~~~~FLOOR _____ ~~~~~~~~Treated wood posts are placed in A ~~~~~~~~~~holes and held in place by back- filling with tamped earth to form the elevated foundation of this home in Virginia. The posts are terminated at the bottom of the floor joists, and anchored to them by bolted connections. POSTS EXTENDING TO ROOF In this New Orleans house the posts are anchored to a concrete pile cap with steel angle clips and reinforced with concrete plinth blocks. The wood posts go through to the roof to tie the whole structure together for hurricane-wind protection as wellI as flood protection. POSTS ENTENDING TO ROOF Wood posts are extended to the roof in this house on Mobile Bay. The posts are set on concrete footings in the sandy shore soil. The weakness of this design is the placement of mechanical equip- ment under the house where it is exposed to flooding. pp~~~~pp~~~ i .. POSTS TERMINATED AT FLOOR These elevated condominium apartments in Mississippi present an interesting form. Note the lateral bracing and the use of stairs to visually shield much of the post foundation. POSTS EXTENDING TO ROOF This house in Pass Christian, Miss- issippi, has wood posts that tie the structure together for hurricane . j protection as well as flooding. Note that severe storms have broken the surrounding trees. POSTS TERMINATED AT FLOOR The primary structural support for this Delaware home is provided by posts set in concrete and termini- nated at the floor. Wood posts ex- tending to the roof support the frontal overhang and first floor deck. 1-9 WOOD POSTS POSTS TERMINATED AT FLOOR Three elevated residential homes on the Eastern seaboard illustrate different types of breakaway paneling used to screen the '' elevating wood posts. Note the use of decks on the raised first floors which give added recreational space. t 1-10 STEEL POSTS POSTS EXTENDING TO ROOF Mies van der Rohe designed this house to avoid flood damage from the Fox River in Piano, Ill- inois. The building is supported on eight steel columns anchored in concrete. The columns are oversized for aesthetic purposes. POSTS TERMINATED AT FLOOR POSTS TERMINATED AT FLOOR Steel posts anchored to concrete footings elevate these apartments in Long Beach, Mississippi. POSTS EXTENDING TO ROOF This contemporary steel frame Illinois house is elevated above the flood plain on wide flange steel columns. The columns are welded to the frame and anchored in concrete footings. 1-11 WOOD PILES WOOD PILES TERMINATED AT FLOOR The ground level of this wood pile home on the coastal flood plain was enclosed to provide storage and garage spaces. The infilled spaces and land- scaping tend to screen the pile construction. WOOD PILES TERMINATED AT FLOOR Infill panels and fencing are used : effectively to reduce the harsh visual impact of the treated wood piles elevating this structure. The piles were driven approximately 16 feet into the sandy soil of the Delaware coast. WOOD PILES TERMINATED AT FLOOR This house is presented to show the particularly high elevation that is required in some parts of the country to prevent flood damage. The first floor of this home in Plaquemines Parish, Louisiana is raised 13 feet on wood piles. 1-12 WOOD PILES TERMINATED AT FLOOR This A-Frame vacation home on the Atlantic seacoast is supported by treated wood piles driven into the soil deep enough to contend with shifting sand and coastal surges. 1-13 CONCRETE & MASONRY PIERS CONCRETE PIERS Poured-in-place concrete piers resting on concrete pile caps support the structural concrete deck and wood framing of this apartment complex in Louisiana. CONCRETE PIERS north This house is a wood-frame structure set on concrete friction L. _ I piers. A high water table ; necessitated elevating the structure. . west CONCRETE PIERS This mobiie home in Minnesota rests partially on a small hill at base flood level with predominant support provided by elevating concrete piers. Breakaway wood paneling is used to screen the piers and provide storage and garage space. 1-14 CONCRETE PIER A mobile home on the Maryland coast needed only minimal elevation to raise the residential structure to base flood level. Elevation was accomplished by masonry blocks which are screened by wood skirting around the base of the structure. CONCRETE PIER Poured-in-place concrete piers provide the main support for this elevated two-story home in Rehoboth Beach, Delaware. The -_,__ screened porch and second story balcony are supported at a 36 inch elevation by concrete block piers. v PIERS Poured concrete and masonry block piers provide the foundation for an apartment building in Ocean City, Maryland. The structure is elevated by poured-in-place concrete piers faced with decorative brick. Space beneath the elevated first floor is utilized for parking and common storage area. 1-15 MASONRY PI ERS This home is built directly on the ' ,4t : Gulf of Mexico and is elevated on masonry piers. Design and land- scaping combine to enhance the appearance of the elevated struc- ture. Decades of resistance to flood and storm damage attest to its structural soundness. u 111111ll1 ililllill llJll lltl MASONRY PIERS Landscaping and wood infill panels are used in this low-cost vacation home to enclose ground level space and improve the appearance of the elevated construction. 1-16 WALLS CONCRETE BLOCK WALLS :. Reinforced concrete block walls support the precast concrete tees used for the floor deck of this architect's office. Fill was used at one end of the building to provide easy entry. WALLS The first floor of an Atlantic Coast apartment building is raised above the base flood level with concrete walls that extend the entire height of the structure. The ground floor is used for entry and garage space. 1-17 EARTH FILL Fill elevates this house above the base flood level. This example is typical of modern day construction with fill. EARTH FILL Borrowed fill was used to elevate this house on the Atlantic seaboard above the base flood level. EARTH FILL The first floor of these garden apartments is elevated on earth fill. Note that the swimming pool for the apartments, shown in the left of the photo, is also elevated above base flood level. 1-18 Eleae Foundations DESIGNING ELEVATED FOUNDATIONS: velopment may increase the possibility of INTRODUCTION future flooding if it is not designed to accom- modate the flood risk. The first factor to consider in contemplating the design of an elevated foundation is the appro- It is essential to recognize as well that the priateness of using a raised building construc- cumulative effect of building encroachment in tion strategy. Elevating buildings in the flood plain will obstruct the passage of flood-hazard areas to reduce flood damage is flood waters, causing adverse effects not only just one way to build in a manner compatible for local residents, but for entire river basins. with the flood risk. Several general considera- By restricting the flow of flood waters, such tions bear on the appropriateness of using development raises the flood level locally and elevated foundations to minimize flood upstream, and may also aggravate such other damage. problems as sedimentation, scouring and erosion. Since Congress has made the availability of flood insurance-as well as federal mortgage The floodway concept has been developed for guarantees, mortgage loans, and other lending riverine areas to promote sound development. by federally insured or regulated financial The flood plain should be thought of as two institutions for construction in flood-hazard separate areas: the floodway, located adjacent areas-conditional upon participation in the to the river channel, is the land area required to National Flood Insurance Program, compliance carry the floodwaters to the base flood. This with the provisions of national flood legislation area must be kept clear of obstruction. The and local codes will be a major consideration flood fringe areas extend out from the for both the community and the individual floodway, and should be developed only with homeowner. A thorough review of applicable adequate precautions. federal and local regulations should precede design and construction. Based upon hydrologic and topographic studies, as well as on planning decisions, the Another important consideration is the unique limits of the floodway can be established and characteristics of the flooding which is likely to mapped, insuring that the base flood can be occur in a flood-prone area. A coastal, discharged without increasing the water wind-driven flood is different from either a surface elevation more than one foot at any canyon or riverine flood, thus different charac- point. teristics need to be considered for adequate protection. The geological characteristics of a All communities participating in the National flood-prone area and the environmental Flood Insurance Program are required to adopt conditions and causal factors (wind, hurricane, flood plain management regulations, once storms, etc.) for potential flooding must be sufficient technical information is available, to considered in designing an elevated prohibit fill, encroachments, new construction foundation. and substantial improvement of existing structures within the designated floodway Existing protective works or flood control which would result in any increase in flood systems are another factor which influence the height during a recurrence of the base flood. protective measures appropriate to a specific community or building site. It is important to An analogous concept is used for coastal areas. recognize that flood-control projects have The flood plain is divided into the coastal high sometimes created a false sense of security hazard or velocity area and the general coastal which triggered further construction in flood flood plain. Construction may only occur within hazard areas. This development has, in effect, a coastal high-hazard area if the structure is increased the flood problem in the United elevated on adequately anchored piles to the States because structures built in areas having level of the base flood, and if the space below flood protection works are generally not the structure is kept free of obstruction in order designed to resist and provide protection from that the impact of wave action and wind-driven the floods that may still occur. Thus, such de- water will be minimized. 2-3 Lastly, an important consideration is the Varying soil types, flood conditions, and economic, social, political and especially environmental factors may require the use of geographic characteristic of the community in additional or modified construction techniques which construction is contemplated. Each to effectively utilize any of the three foundation community has different conditions, types described. constraints, and pressures which determine how a flood plain is developed. It is at the corn- The concept of specifying requirements in munity level that all these factors interact. It is terms of a desired level of building performance there that decisions affecting community de- is recognized. A National Bureau of Standards velopment and environmental quality are publication has described the performance weighed against the types of construction that concept as "an organized procedure or can safely be placed in flood-hazard areas. framework within which it is possible to state the desired attributes of a material, component or system in order to fulfill the requirements of the intended user without regard to the specific means to be employed in achieving the results." GUIDELINES AND PERFORMANCE CRITERIA Performance criteria describe objectives in Beyond these general considerations, terms of the desired performance of the build- guidelines and criteria have been developed ing subsystem to be designed. They permit the which, if appropriately used, will reduce flood generation of many alternative solutions which losses. Specifically, the information which fol- yield this performance, and criteria and test lows has been developed for light-frame re- methods are established to assure that the sidential structures utilizing elevated founda- performance requirements are fulfilled. tion systems. The construction guidelines describe various techniques which should be This method of specifying building preceded by the analysis of local codes and requirements is in direct contrast to most flood conditions. The performance criteria state prescriptive specifications, which clearly state desired objectives which the residential the materials of which the building element is structure should achieve. These guidelines and to be made, its dimension, finish and shape, criteria should provide useful counsel, but they and how it is to be installed. are not regulatory requirements. The advantage of discussing specifications in Apart from building on fill, three elevated terms of performance standards is two-fold: foundation techniques are widely used today 1) to inform builders, designers, and home- for flood plain construction: wood post, wood owners who live or are going to build in a flood pile, and reinforced concrete and masonry plain of the general levels of performance the piers. For each elevated foundation type, building should achieve during a flood guidelines are presented for design and condition; 2) to enable designers and home- application. However, caution and professional builders to develop creative and innovative assistance should be used in the application of solutions to flood problems as long as the these general guidelines to specific situations. performance criteria are satisfied. 2-4 DESIGN AND CONSTRUCTION GUIDELINES DESIGN AND CONSTRUCTION FACTORS When column type foundations, such as piers, posts, or piles, are used an effort Five specific design and construction factors are should be made to keep their number to a applicable to raised structures regardless of the minimum and direction of maximum spac- foundation material or method employed to ele- ing perpendicular to the flow. This will vate the structure. These factors are: site condi- help to limit debris build-up and excessive tions, durability and maintenance, insulation, loads on the structure. utilities, and breakaway walls. If it is desired to enclose space at ground level and flowing flood waters are antici- pated, the solid infill panels used to enclose the space should be of a breakaway variety. SITE CONDITIONS Breakaway fencing may also be used in velocity flow situations. If no debris build- A thorough site analysis is essential to the design up is anticipated, the fencing may be de- of a proper elevated foundation and to deter- signed to include voids that will permit the mine the best building placement for minimizing water to flow through it (see Breakaway the flood hazard. Building placement, building construction section, page 2-10). design, and the elevated foundation work to- gether to determine how aesthetically and effec- 3. LANDSCAPING - Landscaping of the tively a building is integrated with the site. The site can provide useful protection against following five site conditions are among those erosion, debris impact, and vandalism as that must be considered to achieve this integra- well as enhance the design of the structure. tion: Trees, plantings, fencing, earth berms, etc., can all provide this dual function of utility 1. FLOOD ELEVA TION-The base flood da- and aesthetics. tum level determines the height above grade at which the first habitable floor of a Trees can be particularly useful as a natur- residence must be built. This height will al barrier for deflecting debris from im- influence the foundation design and help pacting on building foundations. Size, determine the landscaping measures ap- spacing, and placement of trees in relation propriate for flood protection. In most to flood flow will determine their effective- cases, the finished surface of the first floor ness. should be built to or above the Base Flood Elevation, however, in the coastal high Trees, shrubs and other site vegetation also hazard areas, the bottom of the lowest provide valuable aesthetic elements. They structural member should be at or above have the advantage of allowing water to the Base Flood Level. flow freely and with proper placement will not cause dangerous debris build-ups. It should be noted that many small shrubs and trees may be lost-in high velocity floods. 2. DIRECTION OF FLOOD FLOW - A resi- dence should be oriented on its site in a Additional protection for an elevated struc- way that will provide minimum resistance ture can be achieved by altering site con- to the flow of flood waters. This requires tours to channel water around and away that foundation walls extending above from the structure. Earth mounds and grade and solid infill walls at ground level berms may be used to shield a building be constructed parallel to the primary flow from debris impacts that could severely of flood waters. The surface area of such damage the structure. [Refer to HUD walls exposed to flowing flood waters and manuals 4075.6, Compacted Fills and their number should be kept to a minimum. 4075.7, Slope Protection.] 2-5 4. MEANS OF ACCESS AND EGRESS - ance to insure the useful life of the structure. Buildings designed for flood hazard areas The maintenance measures required largely de- should provide some means of emergency pend upon the materials used for the founda- egress and access during flooding. This tion, floor framing and finishing, and the clima- consideration implies a concern for the tic conditions they are subjected to. These safe evacuation of a residence if flood con- maintenance measures fall into four general ditions make it necessary and for the com- categories: 1 ) treatment of foundation and munity's continued ability to provide floor framing materials, 2) care of the under- police, fire, and health services during a side of floor deck, 3) care of exposed structural flood. connections, and 4) care of ground area. The individual home owner can deal with 1. TREATMENT OF FOUNDATION AND this problem by assuring that some part of FLOOR FRAMING MA TERIALS - The his home will be accessible by rescue boat durability of the primary foundation and and that this accessible portion will pro- framing materials, concrete, steel, and vide some means of exit and entry such as wood can be improved by chemical treat- a door, deck, or window. Provision should ment and coatings. In the case of wood also be made for safe access to a residence's the individual wood members will be roof from within the structure through best preserved by pressure treatment with some type of locking roof latch. Occu- any one of a number of chemical preserva- pants could be forced to the roof by flood tives. These preservatives make the wood waters rising faster and higher than antici- resistant to fungi attack, insects, bacteria, pated. The roof could also provide a good rot and marine borers. Local conditions, pickup point for helicopter rescue. requirements, and cost will determine the best treatment for each foundation. The Community strategies for confronting American Wood Preservers Institute this access problem could include any or (AWPI), with offices at 1651 Old Meadow all of a wide variety of alternatives. Some Road, McLean, Virginia 22101, can pro- of these alternatives are: raise roads and vide information for your specific needs. driveways in flood hazard areas; provide fire, police and health services with the Steel framing and foundation members proper emergency vehicles; develop early below the base flood can be pro- flood warning and evacuation plans; re- tected by galvanization or by painting quire homes in the flood areas to have with rust retardant paints. The need for emergency flood kits containing such painting can be eliminated through the things as first aid supplies, inflatible raft, use of surface oxidizing steels (high fire extinguishers, emergency food and strength low alloy). The American Iron water, signalling devices, etc.; and lastly, and Steel Institute (AISI) can assist in develop good flood plain management answering particular questions on steel regulations. and its maintenance requirements. AISI's main offices are at 150 East 42nd 5. DRAINAGE - Good site drainage should Street, New York, N.Y. 10017. allow flood waters to recede from a site without eroding it or leaving standing wa- The durability of reinforced concrete ter that could cause structural deterioration and masonry block can be improved by or produce a health hazard. the use of chemical additives mixed with the concrete and mortar and by special treatments and coatings. Additives are numerous and vary from those that will DURABILITY AND MAINTENANCE prevent spalling due to freezing to those that will improve strength. Surface treat- A building elevated above grade with the under- ments and coatings, such as silicone and side of its floor area exposed to climatic and epoxy paints, can be used to reduce wa- flood conditions will require special mainten- ter absorption and penetration, and to 2-6 prevent damage by airborne pollutants. galvanized bolts and connecting hardware. Corrosion of reinforcing steel in concrete Connections can be improved further with that may be subject to salt air and salt protective flashing, by treating saw cuts water conditions can be minimized by and drill holes with preservative, and by using galvanized reinforcing. The condi- painting the connections. Protection can tions a particular foundation will be sub- also be provided by enclosing connections ject to will determine the methods that so they are no longer exposed to the should be used to improve its durability weather. All exposed connections should and lower its maintenance requirements. be designed so that water will not collect Guidance in the use of concrete can be on or in them. obtained from the Portland Cement As- sociation, Old Orchard Road, Skokie, 4. CARE OF GROUND AREA - Ground Illinois 60076. The National Concrete Ma- space under an elevated structure that is sonry Association, 2009 14th Street North, not used for parking, storage, recreation, Arlington, Virginia can answer questions on or other purposes should be maintained in concrete masonry construction. a manner that will prevent fire or health hazards from developing (e.g., trash and/or 2. CARE OF THE UNDERSIDE OF THE garbage accumulation). Such ground areas FLOOR DECK - The climate and the de- should be surfaced with a material that will sired appearance will determine whether or minimize erosion and water runoff. Crush- not the exposed underside of a floor ed stone or vegetation appropriate to the should be sealed. Sealing exposed floors area are two surfacing solutions. These will protect subfloors and joists from the comments apply equally to structures that elements, improve insulation, and help con- are not elevated to a height where the ceal utilities. ground space becomes usable. The material used to enclose floor spaces may be inundated by flood waters and thus INSULATION should be resistant to water damage or in- expensive to replace if it is not resistant to esuc ae teo grelae i sood r sthat tExposed floors of elevated residences have to be such damage. Exterior grade plywood that isu dage.xterio rvate pwooe tate insulated against heat losses and heat gains just is treated with preservatives is one water resistant material that would be satisfac- as the walls and roof of the structure do, except reisttmactht ould ntbe usa- there are additional special factors that must be tory. Gypsum products should not be used story. Gypsum products should not be usedconsidered. First, elevating a building will ex- unless an acceptable level of performance pose plumbing to freezing temperatures. Such ~can be demonstrated. plumbing must be insulated against freezing. In Regardless of the material used to seal the extremely cold climates, heating cables may be underside of a floor exposed to the ele- necessary with the insulation. Second, insula- underside of a floor exposed to the ele- ted floor decks may be subject to inundation ments, some provision must be made to al- d oores mabe cod and should therefore use impermeable closed low water that may find its way into the flow sdwi h r fdin ito dayintout pore insulation able to withstand water submer- floor sandwich during flooding to drain out foandwichrthein i to dray out. sion or insulation that can be economically re- and for the joist spaces to dry out. placed. Third, insulation should meet fire code 3. CARE OF EXPOSED STRUCTURAL requirements (see Figures 2-1, 2-2, and 2-3). CARE OF EXPOSED STRUCTURAL CONNECTIONS - The nature of elevated construction exposes many structural con- nections to the elements and possible inun- UTILITY AND MECHANICAL SYSTEMS dation by flooding. This exposure will cause deterioration of vital structural links .Fesidences are generally served by gas, plumb- unless measures are taken to prevent it. ing, sewer, electrical, fuel, and telephone utility systems. These systems are most vulnerable to Some effective measures to prevent the water and impact loading damage from the deterioration of connections are the use of point they leave the ground to' the point they 2-7 1 i gl Insulation Base Flood Exterior Grade Plywood / J a - Water Res. Gypsum Board Base Flood Elevation , Insulation / . . I _ 3Strap-Bolt Joint to Pole Pl _ Pen umn r ..n-;/-' rF~.�:'� E ~ / Base Flood Girders \ Pier I ~ ! /Elevation (CHHA) Plywood Skin Pole Bolt .E~-C w Insulation 3ase Flood Level -m NI Coastal High lazard Area ----- Ext. Grd. Plywood :,HHA) I \\ \\Gal. JoistStrap lWQU~ ~Wood Post FIGURE 2-3 Double Insulated Floor Plenum Space Pier Foundation FIGURE 2-1 Insulated Floor Section on Wood Post Foundation enter the elevated residence. One means of achieving some measure of protection for - i _Water Resistant Gypsum Board these ground to house utility links is to bring i -" ExteriorGrade Plywood all the utilities together in one linkup core that I 1 Xm BaseFlood Elevation is itself designed to resist flood forces. Chances for flood damage to utility distribution systems in the home can be reduced by limiting as much of these systems as possible to ceilings and walls. Electrical outlets, for instance, \cdtii Screened Vent/Drain should be fed from the ceiling rather than the TaJi .- . floor. \-cntinioous Screened Vent/Drain The heating, ventilating, and air conditioning --Exterior Grade Plywood equipment of a home should be elevated above the base flood level. An attic location, if available, would provide the equipment maxi- mum safety. Low points of duct work should FIGURE 2-2 Section be fitted with drains to bleed off any flood Insulated Floor Section water that gets into the system. Foundation Wall The following drawings demonstrate some of these concepts: 2-8 Overhead Energy/Cornmunicatio'n Lines Attic Water Heater Serves as Temporary Large Attic Space' Gravity Water Supply for Dry Storage Attic Furnace Temporary Sink I Drain to Outside Sealed Well Head Base Flood Level 7A. _7 Base Flood Level - jW~~~~~~~~~~r~~~l~~~- ... ~ ~ ~ ~ ' 'I.......I'.. r-'-(CHHA) Pump I FIGURE 2-5 Locating Utilities BREAKAWAY WALLS In some instances it may become desirable for storage or recreation, or necessary because of climate to enclose part orall of the ground level Overhead Energy/Communication Lines under an elevated structure in Coastal High Hazard Areas (CHHA). The walls used to form the enclosed space must be designed so that they do not allow the pressure and velocity force of water and water-borne debris to load the structure excessively. Design techniques to avoid this problem include: walls that break away or fail under flood loads but remain at- tached to the house or are heavy enough to sink and not create a water-borne debris problem, walls that can be detached and stored before a flood, walls that hinge and can be swung out of the path of flood waters and debris, and where ., ~ no debris flow is expected, louvered walls that -- Utilit. Core will allow water to pass through them. All ground level infill wall designs should: 1. Allow flood waters to rise and flow freely FIGURE 2-4 under the structure. Utility Access Core 2. Not permit the infill walls themselves to become water-borne debris. 3. Not cause the accumulation of water- borne debris. Figures 2-6 through 2-9 demonstrate some of the design approaches mentioned above. 2-9 7 7 7 - - I ~~~~~~~~~Removable Wall Panels = 1 (Designed to fail if not - ~~~removed) I FloodFw -S. ~~~Structural Support FIGURE 2-6 Removable Wall Panels Fastened ~~~~~~~Hinged Wall Panels-. 2-10~~~~~~~~~~~~~~I Collapsable Wl-- F~~ood Fk-'w ~~ ~ / -Structural Support FIGURE 2-8 Collapsible Block Wall L-ouvered Wall FIGURE 2-9 Louvered Wall 2-11 POST AND PILE FOUNDATIONS PILE FOUNDATION The safety and satisfactory performance of post This foundation type is constructed of long and pile foundation designs for flood hazard slender wood, steel, or reinforced concrete piles areas depend on the proper analysis of flood that are mechanically driven or jetted into the loads and soil conditions, as well as normal ground. Vertical loads can be carried by piles loads, stresses, and deflections. An architect or driven to a load bearing layer, such as rock (end- engineer should be consulted for this analysis bearing piles) or by driving the piles deep and design. enough into the earth to develop enough fric- tion between the surface of the piles and the The following guidelines for post and pile foun- surrounding soil to carry the load (friction dations are a collection of design and construc- piles). Friction piles also have an end-bearing tion ideas intended to show those who plan to component. build post or pile foundations in flood hazard areas some of the techniques currently being Although post and pile foundations are similar, used. one important difference should be noted-piles are mechanically driven or jetted while posts are Wood, concrete, or steel can be used for posts or set in pre-dug holes. Both may use wood poles. piles. The material that is selected should pre- sent no special difficulties since there are well The availability of'pile driving or jetting equipl- known techniques for dealing with each. ment and skilled operating crews in a particu- lar area may influence the selection of the pile technique. The selection of piles or any other elevation technique, however, should not be based solely'upon the local availability of men, equipment, 'or materials. Structural"require- ments and site conditions will also influence POST FOUNDATION the selection. For example, if heavy scour is anticipated, piles should be used rather than This type of foundation utilizes long slender posts. wood timbers or steel columns set in pre-dug holes or on concrete footings, piers, or pile caps. The timbers may be round, square, or rectangu- lar in section--the square and rectangular sec- tions being easiest to frame into. Steel columns The depth posts or piles should be embedded is can be found in all these sections plus wide determined by local soil conditions, vertical flange sections and numerous others. loads, lateral loads (wind, impact, hydrodynam- ic, etc.), anticipated scour, uplift, and spacing Post foundation holes are dug by machine or by and size of the posts or piles. The following hand. Bearing capacity and stability is improved comments and sketches explain some of the by pouring a concrete bearing pad at the bottom embedment techniques used in wood post and of the hole and/or pouring a collar around the wood pile construction (steel and concrete post after it has been partly backfilled. would be similar) to provide adequate stability and bearing capacity. Post foundations may be set by hand or ma- chine. The longer and heavier the posts become WOOD POST FOUNDA 4lof-Wood posts the more necessary machinery will be. Sixteen are generally embedded 4 to 8 feet. Hole exca- foot wood posts are about the maximum men vations beyond 8 feet become uneconomical. can handle safely without machine assistance. If design loads are small, and the allowable soil The post type foundation must be adequately bearing capacity is adequate the post may be anchored and braced to resist both normal and set on undisturbed earth at the bottom of the flood loading conditions. hole and then backfilled (see Figure 2-10). 2-12 i-Wood Post Back fill Backfilling the hole with concrete rather than Grade---s gravel or sand, as shown in Figure 2-12, adds stability to the structure and increases the bear- ing area as in Figure 2-11. Shallower embed- qment is also permitted with this method. Figure 2-13 shows a variation on the total con- crete backfilling method of Figure 2-12. Here the upper portion of the hole is backfilled with concrete to form a collar and the lower portion "'j\ I.. '~'"is backfilled with sand or gravel. This concrete collar has to be a minimum of two feet deep and reinforced with wire mesh to be effective in providing more rigidity to the structure and per- Foundation Bearing Area mitting shallower embedment. FIGURE 2-10 If extremely poor soil conditions are encounter- Earth Bearing ed it may be necessary to drive a group of piles and cast a pile cap for each post to bear on. This is demonstrated in Figure 2-14. For larger loads and/or poorer soil conditions, Wood posts may also be raised entirely (see Fi- a concrete pad should be poured into the bot- gure 2-15) out of the ground on concrete piers. tom of the hole as Figure 2-1 1 shows. The pad More thorough maintenance is possible with should be approximately as thick as % its dia- this approach but additional bracing may be re- meter with a minimum thickness of 8". quired for lateral stability. : Wood Post -WoodPost I Backfill N Backfill (Concrete) Grade~- Grade-& fl.,,. ?.r Foundation Bearing Area Foundation Bearing Area FIGURE 2-11 FIGURE 2-12 Post on Concrete Concrete Backfill Bearing Pad 2-13 i i l VG r~~~~~ Wood Post I I _Wood Pole Anchor Strap - Gralot- Pier 7L 1' I /l ~ ~ _ i_ iGrade Two Foot | , X Minimum r |I Collar I I Reinforced I ( Hooked Rod I!I l I l Concrete | __ .- I Pier to Footing Collar Permits ,-' -ei-f--- f I : I l | Shallower . . -/ +- ':/ '_ Ebedent f I o /'-- Reinforced of Pole , Footing ---'l F -- --~~~~~~~z'-o-ot-i--' i I r~~~~~~+<f--~~~~,,'" FIGURE 2-13 FIGURE 2-15 Concrete Collar Post-Pier Foundation HOLE SIZE- In post construction the hole should be a minimum of 8" larger in diameter than the greatest dimension of a post section. -Wood Post This allows for alignment and backfilling. , Plinth BACKFILLING - A clean well consolidated /,; I~~~ < > Abackfill is necessary to assure a structure of good ! __ \ t'I alateral stability and resistance against wind and '_ J \ 'Grade _ water uplift. Some of the common backfill ma- ___- ~/ k 1, terials are: sand, gravel, crushed rock, pea -; '!-~ 4 \ gravel, soil cement, concrete, and earth. lPl - wPile Cap Most backfill materials should be mechanically I --I- i-' _ i 4,.- ' /,,x tamped to adequately consolidate and compact ,-' I i r l;Of- them. Wetting backfill materials such as earth L_j,,I I/ or gravel will help their consolidation. L{;~ '[J P i les Soil cement is an economic alternative to con- 'i' ......I crete and attains strength nearly equal to it. I 8, I~ |Soil cement is made by mixing the earth remov- ed from the dug hole with cement in the ratio of 5:1 (earth:cement). To achieve the best re- FIGURE 2-14 suits all organic matter should be removed from Pile/Pole Foundation -- Low-Load Capacity Soil the earth and it should be sifted to remove all the earth and it should be sifted to remove all particles larger than one inch. 2-14 Granular type fills that provide good drainage is placed into the concrete and secured to are generally considered the best. Drainage bracing restraints to prevent penetration around the posts or piles at grade level should be through the footing while the concrete sets. positive to keep water from collecting and deter- iorating the posts. 2. The metal fastening method of anchorage can be used above or below ground. Figure 2-17 has a square wood post lag bolted to ANCHORAGE a metal shoe that is anchored in a pier. In Figure 2-18, heavy gauge galvanized steel Good anchorage of posts or piles to the ground straps are used to anchor the wood post is essential to preventing wind and flood forces to a concrete pad. from overturning or uplifting elevated struc- tu res. PILE ANCHORAGE - In the case of piles, re-4 search and experience indicate that the friction -wood force of earth against the sides of the pile will Post support the major portion of the vertical loads. The allowable frictional capacity, however, may X vary from one code to another. Lateral loads Reinforced Anchor Shoe will be discussed in the bracing section that ~ n~t foll Iows. Pier r POSTANCHORAGE - Two ways to anchor Ait-- post foundations are to 1) embed them in con- Grade- ,_ 3- crete or 2) to fasten them to metal straps, angles, I plates, etc., that are themselves anchored in con- 1-- * crete footings, piers or pile caps. Anc hor olt I I ~~embedment 1. Figure 2-16 shows one method of anchor- ing wood posts in concrete. Large spikes A or lag bolts (5/8" to 3/4" dia.) are driven I into the post around its base prior to pour- FIGURE 2-17 ing the concrete footing. Once the con- Metal Angle Anchorage Detail crete footing has been poured, the post Wood Pole- Wood Post alvanized Strap Spke ora o- -oting Lag~~~~~~~~~~~)~ 4 Scew FIGURE 2-18 FIUE2-16 Galvanized Strap Anchorage Spike Anchorage of Pole Detail 2-15 BRACING servative and fastening the rods with nuts and cast beveled washers (see Figure 2-20). Welded Post and pile foundations are braced when it is connections or drill-holes could be provided in determined that their size, number, spacing,and steel post or pile foundations for similar bracing embedment condition will not be sufficient to schemes. The usual size of the rods is 5/8" to resist lateral forces. The most common methods 3/4" diameter. for bracing post and pile construction are: wood knee and cross-bracing, threaded rods, guy wires, floor diaphragms, and shear walls. If a post structure is laterally braced it will re- duce the embedment to a depth that is neces- sary to prevent uplift, drift, and slippage. The minimum depth required for posts is 4' or solid rock if it is reached in digging. WOOD KNEE AND CROSS BRACING - Knee " bracing, shown in Figure 2-19, is usually 2" X 6" lumber nailed or bolted between the floor joist and post or pile. Cross-bracing is bolted or nailed at the base of one post or pile and fasten- ed in a like manner to the adjacent post or pile just below the floor beams. Rod Bracing FIGURE 2-20 Rod Braced Post House Rod bracing is particularly suited for use in areas where water, debris, and wind forces could be extremely large. This is because the rods pro- vide adequate strength while presenting a rela- tively small surface area to water, wind, and debris. GUY WIRES - The unsightly nature of this method as well as the inherent possibility of FIGURE 2-19 accidents (clotheslining of people and pets) sug- Knee Brace gests that it be used with caution and primarily where other methods of bracing are not pos- sible. SHEAR WALL BRACING - Shear walls can be THREADED RODS - Rod cross-bracing for used to brace post and pier foundations if they wood posts or piles is accomplished by fitting are carefully designed and installed. The shear the rods through drilled holes flooded with pre- walls must be rigid under the design loads and 2-16 firmly attached to the posts or piles to prevent them from moving. The nails, plywood sizing, Plywood Subfloor shear wall edges (chords), and tie downs are all & ShearDiaphrg factors in the proper use of this method of bracing. A shear wall storage room or stairwell is a possible use of this method of bracing (see Figure 2-21). FIGURE 2-22 Floor Diaphragm Bracing -~~~'~~�i 1~~~10y4 ~Diaphragm Floor~~ liii ~~Key__ hearll woi Wall FIGURE 2-21 NA Shear Wall Braced Post House FLOOR DIAPHRA GM BRA CING -Used inLJ conjunction with a shear wall or a concrete key steel Joist wall, a floor diaphragm can be used to transfer Anchor horizontal forces or reduce embedment when solid rock is reached when digging foundation holes. The floor diaphragm can be used with FIGURE 2-23 either pole frame or platform construction. KyWl eto Floor diaphragms usually call for the use of 1/2yWllScto to %" plywood. The application of the floor dia- phragm with a concrete key wall is a practical solution for sloped, rocky sites. The downhill posts or piles can be embedded a minimum FRAMING METHODS - There are two differ- depth and the uphill line of the structure is ent methods for framing into post or pile foun- fixed rigidly through the key wall (see Figures dations that are in common use today. These 2-22 and 2-23). are 1) platform construction and 2) pole frame construction. FRAMING AND CONNECTIONS 1. Platform construction entails simply cut- ting posts or piles off at the desired eleva- The connection of a post or pile foundation to tion and framing them with beams to sup- the framing system of a structure is influenced port floor joists and deck. The platform by three factors: 1) the method of framing thus formed serves as the first habitable used, 2) the cross sectional shape of the post or floor and construction platform for any pile, and 3) the post or pile material, i.e. wood, type of anchored conventionally framed steel, concrete. structure desired (see Figure 2-24). 2-17 Base Flood Level A basic problem faced in both platform and pole frame construction is alignment of the structural supports. Posts can be easily plumbed and aligned before they are backfilled but piles must Base Flood Level be jacked and pulled into position. Alignment (CHHA) ; StructuralSupport is more critical and difficult for pole frame construction utilizing piles than for platform construction utilizing them. , This alignment problem of piles in pole frame construction and the varying diameter and round shape of wood piles dictates that they be located either on the exterior of the building or on the interior but not in the walls. It is diffi- cult and expensive to make wall finishes meet FIGURE 2-24 the poles at close tolerances (See Figure 2-26). Platform Construction 2. Pole frame construction has the posts or piles extended up to or through the roof with beams framing around them as sup- ports for floor joists (see Figure 2-25). This method securely ties the entire struc- N,' ture together and is excellent for high wind situations. Wood piles are generally driven I butt first in this method because framing into the narrower part of the pole is easier. Base Flood Level Base Flood Level StructuralGrd Support - FIGURE 2-25 FIGURE 2-26 Pole Framing Construction Exterior Pole Framing 2-18 CROSS SECTIONA L SHAPE- RectangulIar and 0' Wood or Metal Gusset Plate square post or pile sections usually require onlyI conventional framing techniques similar to post :-: and beam construction. Round sections, how- ever, demand special concern for the connecting / ~ � \ details. Connecting methods are reviewed in a succeeding section. PLA TFORM AND POLE CONSTRUCTION I CONNECTIONS - Timber connections in plat- � form and pole construction are similar and their design is similar to conventional framing meth- ods thus allowing standard bolting and nailing values to be used. When round poles are used, the framing is somewhat complicated. With round wood poles it is generally best to frame the poles with a pair of beams, girders, or raf- FIGURE 2-28 ters--one on each side. Dapped Gusset Plate Connection The roundness of wood poles is not considered when using bolted or spiked connections as shown in Figure 2-27. The design of framing is then the same as for any other timber member. 0 ~~~~~~FIGURE 2-29 b 0 ~~~~~~~~~Dapped Pole Connection I) i ~~~ Spike grid connections (see Figure 2-30), stan- dard in bridge and warehouse construction, are FIGURE 2-27 less familiar to the home builder. A single cur- Bolted Connection toved grid inserted between the pole and the beam Rolted Ponnecint substantially increases the strength of the bolted Round Pole ~~~connection. With the curved side of the grid against the pole and over predrilled holes, a high strength threaded rod is used to squeeze the two wood surfaces together forcing the tooth of the spike grid into the grain of both members. Another method of connection is to eliminate The high-strength rod is then replaced with a the curve of the pole by clapping and then con- conventional bolt of the proper size. Each nect with bolts, nails, gusset plates, or other single curved spike grid with a % inch bolt has a connecting devices. As Figures 2-28 and 2-29 carrying capacity of 3800 lbs. in shear and with show, a dapped pole willI form seats that assist a one-inch bolt a capacity of 4100 lbs in shear. the beams in carrying verticle loads. Poles that A flat spiked grid is used to connect two flat are small in section, however, should not be surfaces and double curved spiked grids connect clapped. two rounded surfaces. 2-19 Spiked Grid anchored to a properly sized concrete footing and be reinforced. A 12" x 12" pier should be the minimum size used for flood hazard construction (see Figure 2-31). / REINFORCED CONCRETE MASONRY - This type of pier is constructed of hollow concrete masonry units anchored to a concrete footing �1 I '~~.L1~L (see Figure 2-32). This hollow cells of these units should be filled with concrete and rein- forced sufficiently to resist the anticipated loads. A minimum pier section for this type of construction should be considered 12" X 12". ~ !.'. fl( LLPOURED-IN-PLACE CONCRETE PIERS- . )~ ~ /)~ ~Piers of this type are essentially reinforced con- crete columns. They are cast in forms set in machine or hand dug holes. The holes may be widened or belied at the base to form a footing FIGURE 2-30 Spiked Grid PIERS Pier construction is another common technique for elevating structures in flood hazard areas. The special loading conditions associated with flooding make it essential that an architect or or St engineer be consulted for the design of pier foundations. The guidelines which follow review some of the common types of piers and methods of pier con- Reinforced struction. Specific site conditions, base BrickPier 12 flood level, soil characteristics, cost considera- Grade tions, and material and labor availability will de- termine which type of pier, if any, is appropri- Reinforced--Anchor ds ate for a particular site. Additional guidance for Footing . the design of pier foundations can be obtained in section 601 of the 1973 edition of the HUD Minimum Property Standards. in TYPES OF PIER FOUNDATIONS 24- ~ ~ - Pier foundations are classified here by their mat- 2i".N24 erial-brick, reinforced concrete masonry, and Minimum poured in place concrete. REINFORCED BRICK PIERS - Brick piers are an effective means of elevating residences. FIGURE 2-31 It is essential, however, that they be securely Brick Pier 2-20 Pouredncr Cap Bolts integral with the pier, or a separate footing may be poured (see Figure 2-33) or if the soil condi- tions are right the footing may be eliminated all together and loads left to end bearing and -12"x 12" friction between soil and pier. Masonry Reinforcing Z f B lock Rods PIER DESIGN AND CONSTRUCTION ~~~i ~~~~< ~~Each pier of an elevated pier foundation should be designed and constructed to function as an I ~~~~~~~~independent structural element in supporting ____________ ~~~~and transmitting building and environmental Grade ~~~~~~~~~~~loads to the ground. .~~... SIZE AND SPACING OF MASONR Y PIERS - The height of reinforced concrete masonry piers Reinforced I I 8"Min. ~~should be limited to a maximum of ten times Footig[ their least dimension. And if the piers are ree- -- - -~~~~~~~~~~ ~tangular (square piers are preferred) the longer -~~h- ~ - -- - ~ dimension should not exceed the shorter dimen- -~ - 24'~24" sion by more than 50 percent. \-' S..., -- Minimum According to the National Concrete Mvasonry ------------- Association, the allowable working stresses for FIGURE 2-32 concrete masonry piers are the same as those for Reinforcedl Concrete Masonry Pier the design of concrete masonry walls. The pier masonry should be laid with type M or S mortar. The association also recommends that the spac- Anchor Strap ~~~~~~ing between piers supporting floor joists should Anchor Strap ~~~~~~not exceed 8' in the direction perpendicular to Reinforced ~~~~~~~~~the joists, nor 12' in the direction parallel to Concrete joists. P~~~~ier All of the minimum requirements listed above IaF apply whether the pier is free standing or later- I ~~~~~~~~ally supported. I I ~~~~~~In cases where exceptionally large loading condi- I I ~~~~~~tions may exist, the pier cross-section will have II ~~~~~~~to be increased and/or additional reinforcement Grade I added. A larger cross-section may be obtained I I a-~~~--- by using pier walls. Reinforced masonry or Iii ~~~~~~~poured-in-place concrete should be used to con- - - ~~cd1.~I ;.... -'f struct these pier walls, which are several feet or Rein forced 4 ~Min. more in length. The long dimension should be Footing :placed parallel to the flood flow, as the example -~~~ ~~vn-r~~~- ~in Figure 2-34 shows. -- Minimum SIZE AND SPACING OF POURED-IN-PLACE L - - PIERS - Plain and reinforced concrete piers are designed as columns. The design should be guid- FIGURE 2-33 ed by the American Concrete Institute's (ACI) Reinforcedl Concrete Pier standards and formulas with special concern for 2-21 DEPTH OF FOOTINGS - Four factors work to determine footing depth: Flood Flow Direction 1. FROST - The bottom of all pier footings should be placed below the locally accep- Reinforced Wall ted extreme frost penetration level. 2. FLOOD HAZARD LOADINGS - In areas I I where flood loadings or wind loadings are Grade expected to be high, deeper than normal --'m- -W ~1-- 1----GZ~-~footing may be required to resist the in- _ _ _ _ . .] ~ �creased lateral and uplift forces (see Performance Criteria A-i, page 2-30). J-A4 2I t - r-- Reinforced I ,IFooting 3. SCOUR- In locales where scour may oc- cur the pier footings must be located well .. -_- ',I below anticipated scour depths. 4. HIGH VOLUME CHANGE SOILS- Foot- ings for pier foundations located in areas FIGURE 2-34 known (or determined) to contain soils of Wall Foundation high volume change potential should be designed with the recommendations of a qualified soils engineer. This type of soil could create complex problems and should be dealt with cautiously. the flood loading conditions. For single family housing their size will range around 12" in dia- FOOTING REINFORCEMENT- All pier foun- meter or 10" X 10" square. dation footings should be reinforced and tied in- to the piers. The reinforcing will either be Spacing of concrete piers is dependent on the welded-wire fabric for light loads or steel bar type of framing used and on the building and reinforcement for heavier loads. Piers and foot- environmental loads. ings can be tied together by hooking reinforc- ing bars around the reinforcing in the footings FOOTING SIZES - Pier footing sizes are a and extending them into the piers (see Figures direct function of soil bearing capacity and 2-32 and 2-33). loading and are easily computed. There are, however, certain minimums that should be The following table (Table 2-1) summarizes observed and these are 24" X 24" X 8" mini- some of the major requirements for pier con- mum footing for masonry piers and 20" X struction that have been presented in this pier 20" X 8" minimum footing for concrete piers. guidelines section. TABLE 2-1 MINIMUM PIER REQUIREMENTS Pier Min. Pier Min. Footing Pier Spacing Useful Material Size Size Right Angles to Joists Parallel to Joists Elevation Range Brick 12" x 12" 24" x 24" x 8" 8' o.c. 12' o.c. 18" to 6' Concrete 12" x 12"or 24" x 24" x 8" 8' o.c. 12' o.c. 18" to 8' Masonry 8" x 16" 20" x 24" x 8" Poured-in- Min. 12" dia., 20" x 20" x 8" 18" to 12'+ Place Concrete or 10" x 10" 2-22 FRAMING AND CONNECTIONS plates and clips, 2) plywood sheathing or wood siding, and 3) metal strapping Pier foundations face essentially the same fram- ing and connection problems as the other types 1. METAL FRAMING PLA TES AND CLIPS- of elevated foundations-they must be designed Figure 2-37 shows how these connectors to resist normal loading and flood loading con- can be used to secure joists to beams. A ditions. The two critical areas are the connec- tions between floor beams and piers, and the connection between floor beams and floor joists. PIER-FLOOR REAM CONNECTION - Floor beams can be anchored to concrete and masonry piers with steel anchor bolts embedded in the pier and bolted through the beams with nuts and large diameter washers. The bolts should have a minimum �/" diameter and be embedded at least 12" in concrete piers and 18 inches in ma- sonry piers. If floor beams butt on a pier, each beam must be anchored to that pier (see Figures 2-35 and 2-36). FLOOR BEAM-FLOOR JOIST CONNECTION - Uplift and horizontal movement of joists can be avoided by securely anchoring the joists to FIGURE 2-37 the beams by any one or a combination of the Metal Framing Anchors following three methods: 1) metal framing Anchor Bolts at Spl~~i ce Solid Masonry or Concrete - FIGURE 2-35 FIGURE 2-36 Beam Splice on Pier Pier -- Section 2-23 whole structure can be tied together with material for stud wall construction, metal this type of framing hardware by extending strapping provides an acceptable alternative their use to exterior studs and to rafters. for anchoring floor joists to the floor beam. This is recommended for structures in vel- The two most important requirements for ocity flood and high wind areas. the satisfactory usage of metal strapping are 1) use of sufficient number and 2) 2. PL YWOOD SHEATHING OR WOOD SID- proper nailing. As a general guide, every ING - Plywood sheathing or wood siding other joist and wall stud should be anchor- continuously nailed to the floor beam, ed with a metal strap. Proper nailing re- header, sole plate, and wall studs provide quires not only a sufficient number of nails adequate~resistance against horizontal driven into the strap but also the nailing of uplift forces (see Figure 2-38 and 2-39). the strap to the proper framing members. Figures 2-40 and 2-41 identify the most 3. METAL STRAPPING - Where plywood important strapping and nailing connec- or wood siding is not used as a sheathing tions for floor framing. ~~fJ~~~~ Stud 6 ~~~~~Solid Sheathing N~ailed to all Members -- Joist pier FIGURE 2-38 FIGURE 2-39 Plywood Anchorage -- Isometric Plywood Anchorage -- Section 2-24 Strapping Nailed to Studs Strapping Wrapped around Floor Beam Pier -I FIGURE 2-40 FIGURE 2-41 Metal Strapping of Framing Metal Strapping of Wa/I Studs 2-25 PERFORMANCE REQUIREMENTS AND CRITERIA The following performance requirements and likely will be defined in the applicable codes criteria identify a range of considerations which while other load conditions (e.g., flood impact should be addressed during the design of resi- loads) will have to be determined. The following dential structures for flood hazard areas. The loads constitute the design load and should be con- performance criteria do not represent the entire sidered as minimum loading conditions as defined range of items applicable to each requirement. in Criterion A.1: Instead, a selective number of criteria have been presented. During building design, it is these 1) Dead Load (D) - The weight of all perman- criteria which should be extensively addressed. ent construction. The dead load includes: a) the weight of the structure itself, b) the weight The performance requirements and criteria are of all materials of construction incorporated applicable to all structural materials and all con- into the building that are to be permanently struction methods used in special flood hazard supported by the structure, including built- areas. Traditional or conventional construction in partitions, c) the weight of permanent solutions, as well as innovative techniques, are equipment, and d) forces due to prestressing. acceptable so long as the performance require- ments and criteria are satisfied. 2) Gravity Live Load (L) - Gravity live loads result from both the occupancy (floor) and the environment (roof), of the building, as stipulated in the applicable code. These in- DEFINITIONS elude, where applicable, loads caused by soil and hydrostatic pressures. Terms important to proper interpretation of the performance requirements and criteria are de- 3) Wind Loads (W - Wind loads stipulated in fined as follows: the applicable code. Applicable Codes - The system of legal regulations 4) Restraint Loads (R) - Loads, forces, and ef- adopted by a community setting forth standards fects due to contraction or expansion resulting for the construction, addition, modification, and from temperature changes, shrinkage, moisture repair of buildings and other structures for the changes, creep in component materials, move- purpose of protecting the health, safety and gen- ment due to differential settlement or combin- eral welfare of the public. ations thereof. Community - Any state or political subdivision 5) Flood Loads (F) - Loads caused by the design thereof with authority to adopt and enforce flood flood which include: plain management regulations for areas within its 0 Flood induced dimensional changes such jurisdiction. such as swelling of wood or heave of expan- Design Flood (Base Flood)-The design flood is the sive foundation soils, * Water loads as defined in Section 602.0 of base or 100-year flood (see base flood) as established by the Federal Insurance the Corps of Engineers' publication, Flood- Administration for purposes of compliance with Proofing Regulations, aaaa Soil loads as defined in Section 604.0 of regulations. the Corps of Engineers' publication, Flood- In the absence of an FIA designation of the Proofing Regulations. base year flood datum level, the community is permitted to utilize the best available flood Sections 0 and 6040 of ood-Proof data. Regulations are reproduced below: Design Loads - 'The design load is the minimum SECTION 602.0 WATER LOADS loading condition which the building should be Sec. 602. 1 Types: Water loads, as defined herein, designed to resist. Some loading conditions most are loads or pressures on surfaces of the buildings and 2-26 structures caused and induced by the presence of V is the average velocity of the water in feet per flood waters. These loads are of two basic types: second; hydrostatic and hydrodynamic. g is the acceleration of gravity, 32.2 feet per se- Sec. 602.2 Hydrostatic Loads: Hydrostatic loads are cond; those caused by water either above or below the a is the coefficient of drag or shape factor (The ground surface, free of confined, which is either stag- value of a, unless otherwise evaluated, shall nant or moves at very low velocities, or up to five (5) not be less than 1.25) feet per second. These loads are equal to the product of the water pressure times the surface area on which The equivalent surcharge depth, dh, shall be added to the pressure acts. The pressure at any point is equal the depth measured between the design level and the to the product of the unit weight of water (62.5 RFD* and the resultant pressures applied to, and uni- pounds per cubic foot) multiplied by the height of formly distributed across, the vertical projected area water above the point or by the height to which con- of the building or structure which is perpendicular fined water would rise if free to do so. Hydrostatic to the flow. Surfaces parallel to the flow or surfaces pressures at any point are equal in all directions and wetted by the tailwater shall be considered subject always act perpendicular to the surface on which they to hydrostatic pressures for depths to the RFD* only. are applied. For the purpose of these Regulations, hydrostatic loads are subdivided into the following Sec. 602.4 Intensity of Loads: types: Sec. 602.4. 1 Vertical Loads: Full intensity of hydro- Sec. 602.2.1 Vertical Loads: These are loads acting static pressures caused by a depth of water between vertically downward on horizontal or inclined sur- the design elevation(s) and the RFD* applied over all faces of buildings or structures, such as roofs, decks surfaces involved, both above and below ground or floors, and walls, caused by the weight of flood waters above them. Sec. 602.4.2 Lateral Loads: Full intensity of hydro- static pressures caused by a depth of water between Sec. 6022.2 Lateral Loads: Lateral hydrostatic the design elevation(s) and the RFD* applied overall loads are those which act in a horizontal direction, surfaces involved, both above and below ground against vertical or inclined surfaces, both above and level, except that for surfaces exposed to free water, below the ground surface and tend to cause lateral the design depth shall be increased by one foot. displacement and overturning of the building, struc- ture, or parts thereof. Sec. 602.4.3 Uplift: Full intensity of hydrostatic pressures caused by a depth of water between the de- sign level and the RFD* acting on all surfaces invol- Sec. 602.2.3 Uplift: Uplift loads are those which act sign levelss provisions aremade to reduce uplift in- in a vertically upward direction on the underside of tensities as permitted in 611.0. horizontal or sloping surfaces of buildings or struc- tures, such as basement slabs, footings, floors, decks, Sec. 602.4.4 Hydrodynamic Loads: Hydrodynamic roofs and overhangs. Hydrostatic loads acting on loads,regardless ot method ot evaluation, shall be ap- inclined, rounded or irregular surfaces may be resol- plied at full intensity over all above ground surfaces between the ground level and the RFD. ved into vertical or uplift loads and lateral loads based on the geometry of the surfaces and the dis- Sec. 6025 Applicability: ... hydrostatic loads shall tribution of hydrostatic pressures. be used In tne design of-buildings and structures ex- posed to water loads from stagnant flood waters, for Sec. 602.3 Hydrodynamic Loads: Hydrodynamic for conditions when water velocities do not exceed loads . . . are those Induced on buildings or struc- five (5) feet per second, and for buildings and struc- tures by the flow of flood water moving at tures or parts thereof not exposed or subject to moderate or high velocity around the buildings or flowing water. For buildings and structures, or parts structures or parts thereof, above ground level when thereof, which are exposed and subject to flowing openings or conduits exist which allow free flow of water having velocities greater than five (5) feet per flood waters. Hydrodynamic loads are basically second, hydrostatic and hydrodynamic loads shall of the lateral type and relate to direct impact loads apply. by the moving mass of water, and to drag forces as the water flows around the obstruction. Where application of hydrodynamic loads is required, the SECTION 604.0 SOIL LOADS loads shall be computed or estimated by recog- nized and authoritative methods. Methods for Sec. 604. 1 Applicability: Full consideration shall be evaluating water velocities and related dynamic given in the design ot buildings, structures and parts effects are beyond the scope of these Regulations, thereof, to the loads or pressures resulting from the but shall be subject to review and approval by presence of soils against or over the structure. Loads the Building Official. or pressures shall be computed in accordance with accepted engineering practice, giving full considera- Sec. 602.3. 1 Conversion to Equivalent Hydrostatic tion to the effects that the presence of flood water, Loads: ... I-or cases when water velocities do not above or within the soil, has on loads and pressures. exceed 10 feet per second, dynamic effects of the When expansive soils are present, the Building Official moving water may be converted into equivalent may require that special provisions be made in foun- hydrostatic loads by increasing the depth of water dation and wall design and construction to safeguard to the RFD* by an amount dh, on the headwater against damage due to this expansiveness. He may re- side and above the ground level only, equal to: quire a special investigation and report to provide these design and construction criteria. a V2 dh= 29 .where 6) Flood Impact Loads (FI) - The loads caused by the design flood as defined in Section 603.0, "Impact Loads," and Section 605.0, "Hurricane and Tidal Wave Loads" of the 'Equivalent to the level of the base or design flood. 2-27 Corps of Engineers' publication Flood- other similar natural events is beyond the scope of these Regulations and no specific or detailed treat- Proofing Regulations. In the case of Section ment is provided. Concepts and requi rements of 605.0, where no specific guidance is pro- these Regulations may be used as a guide in develop- ing suitable provisions for flood-proofing of buildings vided, design loads shall be recommended by exposed to flooding from these sources. a professional engineer and subject to FIA review. Flood or Flooding - 1. A general and temporary condition of partial Sections 603.0 and 605.0 of Flood-Proofing or complete inundation of normally dry land Regulations are reproduced below: areas from: a. The overflow of inland or tidal waters. SECTION 603.0 IMPACT LOADS b. The unusual and rapid accumulation or run- Sec. 603. 1 Types:... Impact loads are those which off of surface waters from any source. result from floating debris, ice and any floatable c. Mudslides (i.e., mudflows) which are proxi- object or mass carried by flood waters striking against buildings and structures or parts thereof. mately caused or precipitated by These loads are of three basic types: normal, special accumulations of water on or under the and extreme. ground. Sec. 603. i. i Normal impact Loads: Normal impact loads are those which relate to isolated occurrences of logs, ice blocks or floatable objects of normally 2. The collapse or subsidence of land along the encountered sizes striking buildings or parts thereof. shore of a lake or other body of water as a Sec. 603. 1.2 Special Impact Loads: Special impact result of erosion or undermining caused by loads are those Which relate to large conglomerates waves or currents of water exceeding antici- of floatable objects, such as broken up ice floats and accumulation of floating debris, either striking or patrd cyclical levels or suddenly caused by an resting against a building, structure, or parts thereof. unusually high water level in a natural body of Sec. 603. 1.3 Extreme Impact Loads: Extreme impact water, accompanied by a severe storm, or by loads are those which relate to large floatable objects an unanticipated force of nature, such as a and masses such as runaway barges or collapsed buildings and structures, striking the building, struc- flash flood or an abnormal tidal surge, or by ture or component under consideration. some similarly unusual and unforeseeable Sec. 603.2Applicability: Impact loads should be event which results in flooding as defined in considered in the design of buildings, structures and 1 (a) above. parts thereof as stipulated below: Sec. 603.2. 1 Normal Impact Loads: A concentrated - Base Flood (Design or 100-Year Flood)-A flood load acting horizontally at the RD-' or at any point below it, equal to the impact force, produced by a that has a magnitude that may be equaled once 1,000-pound mass traveling at the velocity of the every hundred years on the average. It has a one flood water and acting on a one (1) square foot sur- face of the structure. percent chance of annual occurence. Sec. 603.2.2 Special Impact Loads: Where special im- pact loads are IiKely to occur, such loads shall be con- sidered in the design of buildings, structures, or parts thereof. Unless a rational and detailed analysis is made and submitted for approval by the Building Official, the intensity of load shall be taken as 100 pounds per foot acting horizontally over a one-foot wide horizontal strip at the RFD* or at any level be- low it. Where natural or artificial barriers exist which would effectively prevent these special impact loads from occurring, the loads may be ignored in the design. PERFORMANCE REQUIREMENTS AND CRI- Sec. 603.23 Extreme Impact Loads: It is considered TERIA FOR RESIDENTIAL STRUCTURES IN impractical to design buildings having adequate strength for resisting extreme impact loads. Accord- ingly, except for special cases when exposure to these loads is highly probable and the resulting damages are extremely severe, no allowances for these loads need be made in the design. PERFORMANCE REQUIREMENTS SECTION 605.0 HURRICANE AND TIDAL WAVE LOADS The building, its contiguous structure(s), and its service systems shall be designed to Sec. 605. 1 Applicability: Coverage of loads caused by tlooding related to hurricanes, tidal waves and withstand the Base or Design Flood without: �Equivalent to the level of the base ordesign flood. 2-28 A. Causing unacceptable risks to its occupants be increased by the amount permitted or to adjacent or downstream property in applicable codes for design against owners; load combinations including wind or earthquake load. B. Causing unacceptable health hazards to its occupants; and Where ultimate-load design is used (such as instances where ACI 318-71 * is applicable) C. Sustaining damage of unacceptable magni- load factors are applied as recommended in tude. the applicable standard, and F will be com- bined with L, or factored as if it were a live load for loading conditions 1.1 and 1.4. For all other loading conditions loads (F + PERFORMANCE REQUIREMENT - A Fl) will be combined with W, or considered to be equivalent to a wind load. O The building, its contiguous structure(s), and its service systems shall be designed to with- TEST stand the Design Flood without causing un- | acceptable risks to its occupants or to adja- Structural analysis and/or physical cent property owners. simulation. COMMENTARY The building complies with Performance Re- quirement A if the following conditions are The criterion provides a suitable mar- satisfied: gin of safety against structural col- lapse when the building is subjected CRITERION A. 1: STRENGTH to the base flood. The intent of the criterion is that the margin of The building is designed to resist the fol- safety for these buildings, when sub- lowing loads, acting simultaneously: jected to the base flood, be no less than the margin required for other 1.1 D, L, R, and F buildings not subjected to flooding. It is assumed that loads F may act on 1.2 D, L, R, F, and Ft the building over a long period of time, while loads FI are short-term 1.3 D, L, R, W, F, and Fl loads. Thus the margin of safety a- gainst load combinations containing 1.4 0.9D, R, and F FI need not exceed that provided a- gainst wind or seismic loads. 1.5 0.9D, R, W, F, and Fl The combined load of earthquakes Where the working stress method of design and floods is not considered here be- is used the following provisions apply: cause of the low probability of a flood and an earthquake occurring simultan- 2.1 In load combinations 1.1 through 1.5 eously. all loads are applied as listed or as re- quired by the applicable codes for the CRITERIONA.2: STABILITYAND same load combinations with loads FLOTA TION F and Fl. 2.2 Allowable (working) stresses cannot There shall be a factor of safety of 1.5 be exceeded for loading conditions against overturning, sliding, and flotation 1.1 and 1.4. For all other loading under the following load: conditions the allowable stresses can * American Concrete Institute, Building Code Requirements for Reinforced Concrete (ACI 318-71), ACI, Detroit, 1971. 2-29 0.9D + W + R + F + Fl 1.2 For flow velocities in excess of 5 ft/sec. the hydrodynamic loads in F shall TEST be assumed to act over the entire width of the building, perpendicular Stuctural analysis and/or physical to the direction of flow, and reason- simulation. able vertical clearance shall be pro- vided for the passage of debris. The COMMENTARY depth of all foundation elements shall allow for the potential effect This criterion provides a suitable mar- of scour. gin of safety against sliding and over- turning. The most critical load combi- TEST nation is being considered. Tie-down devices can be used to achieve struc- Structural analysis and/or physical tural stability, provided it can be simulation. Evaluation of data and demonstrated that deterioration of documentation for design, tests, and these devices during the service life installation; evaluation of plans and of the building, or by flood condi- specifications. tions will not cause the factor of safety to fall below its stipulated COMMENTARY value. Criterion A.3 is designed to prevent structural collapse caused by the ac- CRITERION A.3: PROVISION AGAINST cumulation of floating debris or the DEBRIS AND SCOUR undermining of foundation elements as a result of scour. Part of the pro- Unless it can be demonstrated that the vision is designed to avoid debris flood waters will be stagnant, or that there accumulation. The other part pro- will be no floating debris during the Design vides adequate strength to resist Flood, the following provisions apply: the effects of the formation of a barrier over the entire width of the 1.1 Building on stilts shall comply with Sec- building. Buildings are exempt if it tion 612.2.3 of the Corps of Engineers' can be demonstrated that no debris publication Flood Proofing Regulations. will accumulate and no scour will This section is reproduced below. occur. Sec. 612.2.3 Building on "Stilts": The building may be constructed above tne RFD* by supporting CRITERION A.4: DISRUPTION OF SERVICE it on "stilts" or other columnar type members, such as columns, piers, and in certain cases, walls. SYSTEMS Clear spacing of support members, measured per- pendicular to the general direction of flood flow shall not be less than eight (8) feet apart at the The service systems shall be designed to re- closest point. The "stilts" shall, as far as practi- sist the loads stipulated in Criterion A.1 cable, be compact and free from unnecessary appendages which would tend to trap or restrict with safety margins as stipulated in A.1 free passage of debris during a flood. Solid walls, against disruptions which may endanger or walled in columns are permissible if oriented with the longest dimension of the member parallel human lives. to the flow. "Stilts" shall be of a type that causes the least obstruction to the flow and the least po- tential for trapping floating debris. Foundation TEST supports for the "stilts" may be of any approved type capable of resisting all applied loads, such as spread footings, mats, piles and similar types. Engineering analysis and/or physical In all cases, the effect of submergence of the soil simulation. Evaluation of data and and additional flood water related loads shall be recognized. The potential of surface scour around documentation for design, tests, and the stilts shall be recognized and protective mea- installation evaluation of plans and sures provided, as required (for breakaway walls ation see pages 2-10 --2-12). specifications. 'Equivalent to the level of the base or design flood. 2-30 COMMENTARY The building complies with Performance Re- quirement B if the following conditions are This criterion only applies to disrup- satisfied: tion which may cause fatal accidents, such as rupture of gas lines. Lesser CRITERION B. 1: DISRUPTION OF UTILITY load levels are stipulated in B.1 for CONNECTIONS disruptions which constitute a health hazard. Building utility connections shall be designed to resist the following loads: CRITERION A.5: EXECUTION OF RESCUE At loading conditions: OPERA TIONS 1.1 D+ L+ R+W+ F+ FI The building is designed to permit the execution of rescue operations. 1.2 0.9D + W + R + F + Fl During the duration and at heights of the The building utility connections should Design Flood the building shall: not sustain: 1.1 Allow the safe evacuation of the occu- 2.1 Permanently disrupted and/or broken pants out of the building. attachment with their fixtures and/or supporting structural element; 1.2 Allow the safe transfer of occupants from the building to rescue vehicles. 2.2 Leakage or escape of effluent which could contaminate drinking water; 1.3 Provide means of access or adjacency for rescue vehicles. 2.3 Rupture of electrical service which could cause electrocution and/or fire. TEST TEST Evaluation of data and documenta- tion for design, tests, and installation; Evaluation of data and documenta- evaluation of plans and specifications. tion for design, tests, and installations; evaluation of plans and specifications. COMMENTARY Inspection and/or testing of built ele- ments when deemed essential. De- Criterion A.5 is designed to prevent termination of conformances to gen- the entrapment of building occupants erally accepted codes, standards and by rising water levels. Part of the engineering and trade practices, where provision is designed to provide means applicable. to evacuate the building (e.g., win- dows, roof trap door). The other COMMENTARY parts provide for the accommodation and execution of rescue operations This criterion applies to all utility con- (e.g., by boat, helicopter). nections subject to the forces of the Design Flood. Utility connections which are designed to disconnect dur- ing the Design Flood without the re- PERFORMANCE REQUIREMENT - B lease of deleterious substances are exempt from provisions 1.1, 1.2, and D The building, its contiguous structure(s), and 1.3. its service systems shall be designed to with- stand the Design Flood without causing un- acceptable health hazards to its occupants. 2-31 CRITERION B.2: PROVISION AGAINST CRITERION B.3: PROVISION AGAINST DRINKING WATER CON- CONTAMINATION OF TAMINATION POTABLE WATER WELLS There will be no contamination of drinking Private potable water wells shall not be water with sewer effluent or flood water. contaminated by toxic substances or im- purities caused by the Design Flood. Criterion B.2 and Performance Require- ment B are deemed satisfied if the follow- Criterion B.3 is deemed satisfied if the ing provisions are met. following provisions are satisfied. 1.1 Approved backflow preventers or de- 1.1 Private potable well water is not sup- vices are installed on main water plied from a water table located less service lines, at water wells and/or at than 25 feet below grade, nor from suitable building locations to protect any deeper supply which may be pol- the system from backflow or back luted by contamination entering siphonage of flood waters or other fissure or crevice formations. contaminants in the event of a line break or temporary disconnection. 1.2 Each well is provided with a water tight casing to a distance of at least Devices are installed at accessible loca- 25 feet below the ground surface tions and maintained in good working and shall extend at least one foot order. above the well platform. 1.2 Sanitary sewer and storm drainage sys- TEST tern connections are provided with approved backflow preventers or de- Evaluation of data and documenta- vices installed at each discharge point. tion for design, tests, and installation; evaluation of plans and specifications. 1.3 No storm or flood waters are drained into systems designed for sewage only, Geological analysis of residential site. and vice versa. COMMENTA R Y TEST Criterion B.3 is designed to prevent Evaluation of data and documenta- the contamination of water wells used tion for design, tests, and installation; as a source for potable water. Part of evaluation of plans and specifications. the provision provides against the con- tamination of the water supply source. COMMENTARY The other part provides against the contamination of the water removal Criterion B.2 is designed to prevent system. In any case, local health contamination of drinking water with codes should be consulted. sewer effluent or flood waters. Also, the criterion is designed to prevent da- mage to fixtures and interior finishes (e.g., flooring, wall surfaces) from PERFORMANCE REQUIREMENT - C backflow or back siphonage of flood waters. [1 The building, its contiguous structure(s), and its service systems shall be designed to with- stand the Design Flood without sustaining damage of unacceptable magnitude. 2-32 The building complies with Performance Re- 1.1 Living areas shall be considered habit- quirement C if the following conditions are able areas which provide for the essen- satisfied: tial needs of people: living, sleeping, dining, cooking and sanitation. CRITERION C. 1: PROVISION AGAINST PERMANENTDAMAGE Recreation areas, libraries, and other speciality areas are to be considered Under loading conditions 1.1 through 1.3 habitable areas and therefore should the building as a whole, or any element not be submerged by the Design thereof, shall not suffer permanent dam- Flood. age which would require replacement or major repair, or which would extensively 1.2 The electrical system complies with impair its intended function. Criterion C.2 if the following condi- tions are satisfied: 1.1 D+ L+ R+W+ F+ Fl 1.2.1 All portions of the electrical 1.2 0.9D + W + R + F + FI system installed below the Design Flood level are suitable The criterion is deemed satisfied if deflec- for continuous submergence tion limits under loading conditions 1.1 in water. Only submersible and 1.2 do not exceed those stipulated in type splices are used and con- applicable codes, or if it can be demon- duits located below the strated that deflections caused by load Design Flood level are self combinations 1.1 and 1.2 can be accom- draining if subject to flooding. modated by suitable detail and adequate flexibility of elements. 1.2.2 Lighting panels, distribution panels, and all other stationary TEST electrical equipment are lo- cated above the Design Flood. Evaluation of data and documenta- tion for design, tests, and installation; 1.3 The mechanical system complies with evaluation of plans and specifications. Criterion C.2 if the following condi- Inspection and/or testing of built eie- tions are satisfied. ments when deemed essential. De- termination of conformance to gen- 1.3.1 Heating, air conditioning, and erally accepted standards and engi- ventilating equipment are in- neering and trade practices, where stalled above the Design Flood. applicable. 1.3.2 All duct work for warm air COMMENTARY heating systems which is lo- cated below the Design Flood This criterion assures that the Design level is provided with emer- Flood shall not cause excessive da- gency openings for drainage of mage. Effects of swelling caused by ducts after a flood condition. increased moisture or inundation must be included in F. 1.4 The plumbing system complies with Criterion C.2 if the following condi- CRITERION C. 2: PROVISIONAGAINST tions are satisfied: UNNECESSARY DAMAGE 1.4.1 Tanks, softeners and heaters All living areas, major utilities, furnaces, are installed above the Design and air conditioning units shall not be sub- merged by the Design Flood. 2-33 1.4.2 Plumbing below the Design COMMENTARY Flood level will not suffer loss of stability or loss of Criterion C.2 is designed to prevent tightness that will permit leak- unnecessary damage of living areas, age or physical damage to major utilities, furnaces, and air con- fixtures and joints and con- ditioning units by the Design Flood. nections that will permanently Part of the provision is designed to impair functioning. elevate living areas and equipment above the Design Flood. Other parts 1.4.3 Utility connections designed are designed to prevent the damage to disconnect during the of utilities and mechanical/electrical Design Flood are easily re- connections below the Design Flood. connected. (See Criterion B.1) TEST Evaluation of data and documenta- tion for design, tests, and installation; evaluation of plans and specifications. 2-34 IIIILBIII!IC I�' IIll" IA Brief Survey of Design Improvements _~~~~~ I INTRODUCTION The following residential design concepts were developed to test the applicability and usefulness of the information presented in this manual. Four architectural firms and several architectur- al schools were asked to develop preliminary de- sign concepts for various housing types (single- family, rowhouse, and multi-family), at varying heights above grade, and at a range of construc- tion costs. The design concepts were to be re- sponsive to the research findings and the per- formance criteria of the manual and also to present design ideas to alleviate the unaesthetic appearances often associated with elevated resi- dential structures. Additionally, the designers were asked to reflect the flood hazard condition, material availability, construction capability, social acceptability, and aesthetic characteristics associated with their region. The flood problems of four regions of the country--Northeast, South, Midwest and West--- are represented. The types of floods for each area are described, followed by design ideas for particular cities within these areas. 3-3 NORTHEASTERN U.S. The Atlantic coast regions of the U. S. are often SINGLE-FAMILY RESIDENTIAL CONCEPT subjected to flooding caused by the high winds and heavy rains of violent ocean storms and hur- Designing for a flood-hazard area with a four- ricanes. This flooding is characterized by fast foot elevation requirement and providing low- moving rivers and heavy coastal surges. cost housing required a unique, responsive solution. Because of New England's adverse winter climate, the residence is supported on poured-in-place concrete walls (see Figure 3-1). BRIDGEPORT, CONNECTICUT The walls, reinforced and windowless, with a thick slab and waterbarrier at the slab/wall joint Design concepts were developed for both can be made waterproof. Windows could be single-family and townhouse construction. A included if reinforced and sealed watertight at major consideration of both residential con- floodline. The fill removed during excavation is cepts is the relationship of the occupant and used as an entrance ramp, flood diverter and his automobile to the raised structure. The parking area (see Figure 3-2). Use of excavated architects have provided ramps for both occu- fill for the ramp material is generally satis- pant entry and automobile parking to alleviate factory up to ramp heights of 6 feet. The water the inconvenience of elevated structures to heater, furnace, ductwork and piping are children, the elderly, and the handicapped. required to be located above the base flood. Structurally, however, the residences are quite Here, they are in the attic (see Figure 3-3). different. The single-family structure is sup- ported by a wall foundation and the townhouse is supported by a pier foundation. , : 3-4 ~" 4'Elevation Above Grade 3-4 Direction Stone Revetment . FIGURE 3-2 House Site Plan Overhead Energy/Communication Lines Mechanical Equipment Attic Storage I v l 1~ ?Tankc j --Well Note, Flood-proofed Basement allowed only in exceptional cases under a variance procedure. Because of possible uplift, required weight of building must be checked. FIGURE 3-3 House Section 3-5 TOWNHOUSE RESIDENTIAL CONCEPT With an elevation requirement of 10 feet above grade, the architects have designed these luxury townhouses around a central social deck (see Figures 3-4 and 3-5). Parking is located beneath the deck. Access to the deck and to the town- houses is provided by stairs and a timber ramp. The ramp provides access for children, the hand- icapped and the elderly. During times of flood- ing, the ramp can also be used for driving auto- mobiles and rescue vehicles up to the deck level. Steel girders resting upon concrete piers support both the social deck and the townhouses (see Figure 3-6). The deck has double floors for added insulation and the protection of utility services. ,,,F FIGURE 3-4 Town Houses Raised 10' Above Grade 3-6 v HO FIGURE 3-5 Town House Site Plan Attic Storage Base Flood --~ ~' --~h ~' l Concrete Fod mPier r. I FIGURE 3-6 ~ Town House Section 3-7 CHARLESTOWN AND NEWPORT, design to not only meet engineering require- RHODE ISLAND ments, but to also be cognizant of the visual effect such design will have on the prevailing The architect has chosen two case study areas character of the area in question. with distinctly different cultural and natural conditions that affect flood design considerations. The areas are Newport and Charlestown, Rhode Island. Newport is a corn_ CHAR LESTOWN CASE STUDY pact commercial and recreation center which has many residences along the water's edge. An inventory of critical natural factors was The area studied in Newport is a protected made to determine how and where development harbor with access from Rhode Island Sound should take place in the Charlestown coastal into Narragansett Bay. The portion of Charles- flood plain. As a result, specific land area with- town that is the second study area is a beach in the flood plain was deemed acceptable for re- front area with vacation house development. sidential development. The analysis then pro- Most development is on the outwash plain that ceeded to the evaluation of methods of elevation forms the beach or is directly facing the appropriate to the development area. Atlantic Ocean on the barrier beach. Both study Frnmru ucinladashtcraos areas have high development pressures. Frnmru ucinladashtcraos Obvious environmental drawbacks have not berming with heavy stone revetment was chosen restricted their intense use. Their location on as the method for elevating residential structures the water's edge is scenically delightful, but in the coastal flood plain of Charlestown (see has high risk factors. Until recently, these sites Figure 3-7). The homes were clustered to keep were actively developed with little or no down the cost of fill and because the land avail- concern for flood hazard. able for safe building in the flood plain was lim- ited (see Figure 3-8). A small scale single family In both areas there are historic, scenic and corn- scheme was chosen as desirable for visual con- munity values that should influence the design tinuity with earlier buildings (see Figure 3-9). of elevated structures. In Newport the close On the common bermed area, all houses, a small proximity of the Historic District imposes amount of private space, and all utilities are lo- height, bulk, material, and size considerations cated. Low intensity land uses such as parking, into any planned development.* Similarly in road and driveways, playgrounds, etc., are lo- Charlestown, simply elevating structures within cated on the lower surrounding areas. Ramps the open area of the barrier beach or outwash and steps are used to accommodate the height plain, without regard for the natural environ- differences from parking to the finished first ment, could produce ungainly and visually dis- f loor. tracting elements. It is necessary in flood area *In the case of historic structures in flood plains listed on the National Register of Historic Places or a state inventory of historic places, restoration may be accomplished without elevating the first floor through a variance procedure. Base Flood Level Earth Fill FIGURE 3-7 Section Showing Earth Berming in Charlestown Propasal 3-S FIGURE 3-8 Charestown Development Site Plan Perspective of Charlestown Development 3-9 NEWPORT, RHODE ISLAND CASE STUDY In the area furthest from the water, berming offers flood protection and a gradual level Development in the wharf area in Newport is change from that of the highway. A transitional structured by a combination of natural and cul- middle section combines berming with raised tural conditions. It is in the special flood hazard structures. Level changes are integrated by link- zone, yet its water's edge location makes it ing extended decks with ramps and stairs. In visually attractive. It is separated from the older the area closest to the water, raised structures historic areas of Newport by a highway. which do not alter the water to land relation - Changes in the use of the wharf area and its ships or block views are used (see Figure 3-1 1). new relationships with neighboring areas have Commercial uses are most likely to locate in the resulted in an expansion of commercial and bermed area, where first floor spaces are usable. residential development. The low height above Residential, restaurant, and small office uses are sea level means that new structures will have to more suitable to the raised structures, where in- be raised approximately to the level of the new creased privacy and better views are found. highway to comply with Federal flood regula- tions. Vehicular and pedestrian access must be Spaces under and between the new buildings can considered in the overall plan for the area, also be used for pedestrian malls, and thus reinforce making this an important prototypical example. the tourist and commercial uses of the area. Decks, balconies and trellises can connect differ- Analysis indicates that the optimal solution ent building levels. Utilities for the raised struc- could be a combination of elevation techniques tures can be run beneath these raised decks and because different zones in the wharf area are trellises and then tie into the berm, and thus be suited to different elevation techniques. protected from flood damage. Manipulation of the spaces and level changes created by flood protection can be used to enhance the intricacy and human scale of the wharf (see Figure 3-12). TBase Flood - FIGURE 3-10 Existing Wharf Area in Newport i r~~l BermingX j Raised Structures la6' 5BaseFlood MSL FIGURE 3-11 Proposed Wharf Area Development 3-10 I ~ ~~I ok: s -~~~~~~~~~~~~~~~~~~~~~~~~~~~- UN~ Iw1 FIGURE 3-12 Perspective of Proposed Newport Development 3-11 SOUTHERN U.S. A great portion of the Gulf coast and resting on concrete-capped wood piles driven Mississippi River system is protected by a 20 to 30 feet into the ground. The column network of levees and emergency flood-control material(e.g., wood) is dependent on the devices. The levees provide varying degrees of loading, cost, and architectural considerations. protection from Mississippi River flooding and In this instance, the architects have chosen a hurricane-induced high water. However, where stressed skin (plywood) column. The utility this protection is not totally sufficient to services would be brought from underground protect against the base flood, structures into the residence inside a dummy column. behind the levees may be required to be elevated, although possibly to a lower level. In addition, substantial unprotected areas in New SINGLE FAMILY RESIDENTIAL CONCEPT Orleans and the Mississippi Delta area and along the Gulf coast are subject to riverine or The stressed-skin columns visually organize coastal surge flooding. and highlight this design for a single-family residence elevated 10 feet above grade. The NEW ORLEANS, LOUISIANA plywood columns, resting on concrete-capped wood piles, are designed to resist all loads A modular foundation concept was selected by including flood and lateral loading without the architects as the basis for their design of requiring unsightly cross-bracing. single-family and multi-family housing. It is the architect's belief that aesthetic design should Parking and storage is provided below the incorporate the least number of supports above elevated living area. Second floor balonies grade. assure a means of escape during high flooding as well as providing visual and spatial interest. Consequently, the supporting foundation col- The large windows provide for views and umns are placed on 14- to 16-foot centers ventilation. FIGURE 3-13 Elevated Single Family House Elevated 10'Above Grade 3-12 MULTI-FAMILY RESIDENTIAL CONCEPT and vertical support. Landscaping placed around the bottom of the structure minimizes the ele- Raised 4 feet above grade, this multi-family re- vated appearance of the residence. sidence is both hurricane and flood resistant, as well as visually appealing. Stressed-skin columns of marine grade plywood again provide lateral FIGURE 3-14 Elevated Multifamily Housing Elevated 4'Above Grade 3-13 MIDWESTERN U.S. Flooding in the midwest is of two types: river- Stream Fow ine and lake flooding. The characteristics of both are usually slow rise and low velocity. However, flash flooding and lake shore scour- ing can and do occur. The Great Lakes area, T-o f l s more specifically, the Wisconsin, New York, Ohio, and Michigan lake shores have experienced .-.. ' 'I growing problems of lake flooding and slow ero- sion caused by the increasing occurrence of high i I'I waters and high winds. CHICAGO, ILLINOIS C i The architect has chosen two different founda- tion and structural systems for his design of a 77ZS. X i single-family residence and a garden apartment. The single-family residence is supported by a wood post foundation extended and anchored to the roof. The garden I concrete block walls. Both residential concepts provide parking and entrances from under the j u . building. FIGURE 3-16 SINGLE-FAMILY RESIDENTIAL CONCEPT FIGURE 3-16 House Site Plan Designed for an average income family in the Chicago area, the architects have conceived a FIGURE 3-15 Single Family House Elevated 8'Above Grade 3-14 well-proportioned residence (see Figure 3-15). Wood posts support the structure as well as organize the exterior appearance. To allow the 1F .t passage of flood waters and floating debris, the stream Flow area under the elevated structure has been left as 'il open as possible. The entrance to the structure i , -, is provided by an open stair sheltered by the residence above. Automobile parking and shel- tered relocateable storage is also provided under , the structure. I T - GARDEN APARTMENT CONCEPT f .. - . Although elevated 8 feet and constructed of ,. ....-. reinforced concrete block, this rowhouse does ! A [ not appear to be designed for a potential flood . --L condition. The covered parking and entrance ," < - - * [ .- level is handsomely integrated with the above living levels by reinforced concrete block walls . . .. r .[ _ which organize the entire structure. The walls ' N ' are constructed parallel to the direction of ' -- ... possible water flow as shown in Figure 3-18. o I a L l ' I, Although the entrance to the residence would j - . - be inundated by flood waters, the occupants FIGURE 3-18 would not be and they could evacuate by means Housing Site Plan of a second story balcony. FIGURE 3-17 Garden Apartment Elevated 8'Above Grade 3-15 WESTERN U.S. Pacific coast flooding is generally associated with Parking for both residential concepts is under high seas and rains. Ocean storms accompanied the structure. by high winds have caused considerable erosion and damage to beach and coastal flood plain property. Inland rain storms, on the other hand, falling on the mountainous terrain cause SINGLE FAMILY RESIDENTIAL CONCEPT major canyon and valley flooding. Both coastal and canyon flooding are dangerous high velocity A two way wood post structural grid supports situations. Slow-rising and lower velocity condi- the living units at levels above the base tions occur on coastal marshes and low-lying flood and serves to organize and unify the vari- riverbeds. ous units with a minimum impact on the ecolo- gy of the area. A seven foot clearance beneath the horizontal structural members allows for parking, storage, and sheltered recreation space SAN FRANCISCO, CALIFORNIA separated from and below the living units (see Figure 3-19). The reduced land coverage of this The architect has developed several very in- design is in keeping with the architect's concern teresting and distinctive residential concepts for efficient/effective land use. Shared facilities, for single- and multi-family housing. The use of clustering buildings, etc., further give these landscaping, fences, and exterior decks mini- houses a unique identity and sense of commun- mizes the elevated appearance of the structures ity. Within the prescribed vernacular of poles, while providing functional visual highlights. decks, railings, and fences, architectural variety Structurally the two concepts are quite with continuity is achieved. The fences are different. Although both concepts utilize wood strapped together to prevent pieces from posts, the single-family residence uses a floating away if damaged during a flood. Water two-way structural grid supporting heater and furnace and air conditioning equip- prefabricated housing units, while the multi- ment are located 18 inches above base family structure is conventional wood frame flood level with all ductwork in second floor or construction built upon a wood post'supported attic space (see Figure 3-20). platform. t/ 1 FIGURE 3-19 Single Family Detached One and Two Story Housing Elevated 7'6"Above Grade 3-16 Hot Air Supply Water H-eater 50 gal. Emer. l i l tlte n Supply (min.) . . ____-- __Drains Above the Base Flood Level IBase Flood Level 61 ~~~~Base Flood Level (-for CHHA Gas Electric-- Telephone '0 0 Sealed Well Utilities Vault -- Telephone - $etic Eetrio Tank Gswishutoff, Wter supply FIGURE 3-20 Mechanical Schematic of Single Family House FIGURE 3-21 Perspective of Single Family House 3-17 MULTI-FAMILY RESIDENTIAL CONCEPT To reduce costs, the architects have designed a conventional wood frame structure built upon a wood post platform. Raising the first floor to at least 8 feet above grade provides an oppor- ' ' tunity to put parking under the building. This JI reduces the area of the site that has to be built upon and places cars closer to apartments. How- Flood Level ever, parking under the structure requires fire separation. Exposed entrance stairs and fencing minimize the elevated appearance of the struc- ture while providing visual variety and privacy (see Figures 3-22 and 3-23). FIGURE 3-23 Elevation of Multifamily Housing ..J~ FIGURE 3-22 Perspective of Multifamily Housing Elevated 8'Above Grade 3-18 Cost Analysis of Elevated Foundations t~~ EiIIl| COST ANALYSIS ," Pdi F.lhi Molt -- 2X4 SillCone Sab CndCOII~llb" -' '--6/6dWille Once a community decides that the economic 4x4 .C.. . . . .. risk and environmental impact of developing .I o ,; - flood plain land for residential use is : !7 \ -,~ 4" r-Compate d G-ral acceptable, the dollar cost of that development . . ,o . must be evaluated. Two factors bear significantly upon any such evaluation: first, .I how can you assess the net cost of construc- tion in the flood plain which meets the require-g ments of the National Flood Insurance Program in light of the potential and unpredictable FOUNDATION SECTION hazard of flooding and the losses which may F - ensue; secondly, what are the particular cost Slab-on-Grade differentials between construction on elevated foundations, as required by the National Flood Insurance Program for new structures and substantial renovation in flood-hazard areas, P-.W. D... Embedded 15" Min-- 2.10 Juins and conventional building methods. ..O.C... 2x6 Sill Plate-- -3-2.10 Gdr 4.l86Cap.lao W i- -T-ieSoisid The conclusion is inescapable that the savings ..i la Cap r realized over the lifetime of a structure by- p.., building on a raised foundation, are ' considerable and dramatic when compared with ...:.. - !;aE-t r the one-time increase in construction costs for an elevated foundation. This is especially valid Fa.in' considering the foundation costs are generally 16248in only eight percent of the total cost of a -- 2 residential structure. FOUNDATIONSECTION Crawl Space COST ANALYSIS APPROACH In order to arrive at this conclusion as well as to compare the cost of elevated construction in .:- --| --PliywoodDk the flood plain with the cost of building types . ..." . . . . _ most home builders are familiar with, the ill........... following steps were taken: (it is important to S_-8xCapck l...d..... ld note that the average cost summaries for ele- _r Spido Giod, vated foundations are without regard to the GSor Ft;C Sli EnC ' height of the structure.) R1. T. 1 . .6.Weede. Bldailao per Over ; , Cl. & Set in -Wrle ReinfS ori ng 4 ..... D' e . q Ar Fap e ;ariier 1. Slab-on-grade, crawl space, and basement Cop..et20d.. foundations (see Figure 4-1) were selected CFoif t 2 as three of the most common types of resi- Basement ON dential foundations and detailed drawings of them were prepared. Detailed drawings were also prepared for the three most typi- FIGURE 4-1 cal elevated foundation types. These are CONVENTIONAL FOUNDATIONS post, pile, and pier foundations (see Figure 4-2). 4-3 2. These detailed drawings were distributed I, I __i l , 2.10":ic' nationwide for cost estimates in early 1974. The estimates are summarized in ' - -/, PlB . i' Table 1. They are based on the foundation Bi Si dsor' 2x10Girder ' - and deck of a 1500 square-foot house, _l .pliroinM .- oe.o t 28' x 50' with a small offset (see example, page (4-9). The total cost of this house is in the $25,000 range excluding land. All estimates were based on construction prac- tices acceptable under the FHA Minimum Property Standards for One- and Two-, Family Dwellings and respond to the ob- -ri:L" ':;ii jectives of the performance requirements 2 FOUNDATION SECTION presented in the manual. Wood Posts TABLE 4-1 Foundation Cost Estimates _ PlW.. . . 2.10 Joins 16' O.C. Average Cost Summary CONVENTIONAL FOUNDA TIONS -Iijjt' .--- 2xBG / SLAB-ON-GRADE $1.27 per sq. ft. _.| SpGl Ri . . .. CRAWL SPACE $1.95 per sq. ft. BASEMENT $3.49 per sq. ft. r ELEVATED FOUNDATIONS 1 WOOD POLE $3.35 per sq. ft. WOOD PILE $3.05 per sq. ft. CONCRETE PIER $3.59 per sq. ft. ESTIMA TES--SPRING 1974 rj FOUNDATION SECTION Wood Piles 3. Using the data from this cost sampling, the average cost of each conventional founda- tion type was compared to the average cost 2... . . .B.oC of each elevated foundation type. This eck _ comparison was done in two ways: first, each elevated foundation was shown as a percentage of the cost of each conventional D..bl. 1. . foundation (conventional foundations were established as base 100); and second, each - ' .a..h foundation was shown as a percentage of the cost of the entire house. These cost , l comparisons are explained and graphed in 1; the cost comparison section. 4":~ [liil"� ! ~T 4. The height to which the first habitable . L [I. _" floor of residences will have to be elevated 24 FOUNDATION SECTION will vary depending on base flood Concrete Piers levels and topography. The effect in- creased elevation has on foundation costs was examined. The results are presented FIGURE 4-2 under FOUNDATION COST COMPA RI- ELEVATED FOUNDATIONS SONS. 4-4 5. The next step of the cost comparison analy- These basements must be completely sis was to provide the user of this manual flood-proofed, i.e., watertight and capable with some guidance for interpreting the ef- of resisting the action of the base f lood. fects future material cost variations will have on the cost of elevating residences. 4. Where a community has demonstrated a This is discussed in the Future Factor need for shelter against recorded occur- section. ~~~~~~~~~rences of tornado or severe windstorm, 6. Cot estmatin shets ar inclded a thethe Administrator may grant permission end Cost ethismartin ofsheet arinualudTey atrte for "storm cellars." Such storm cellars poiend tofass theiseprt of this manual.Tear must be designed to insure the integrity poine moassing thise own cost cmparsnual of the main structure during the time of in makin his owncost comarisonsflooding and are limited to non-habitable uses. All electrical, heating and other utilities must be above the level of the COST COMPARISON CONSIDERATIONSbaefod The decision on how to deal with this space Fill can be used to elevate conventional founda- below the elevated floor will affect the cost of tions such as slab-on-grade. The cost of this ap- construction and should be considered in the proach will depend on the availability, quality, total cost picture. and unit cost of fill as well as the height and compaction necessary. The environmental and engineering considerations involved in the use of EARTHQUAKES fill are complex and directly related to local con- ditions. When elevating on fill is being con- Constructing elevated foundations in earthquake sidered as an option a soils engineer should be areas may require additional structural expendi- consulted for technical advice. tures that should be noted in cost estimates. The local building code and a structural engineer should be consulted to evaluate local conditions. LOWER SPACE OPTIONS The space created under a residence by raising it on piles, posts, piers or other such elevated foun- ELEVATED FOUNDATION DEPTHS dation can be treated and used in several ways: The depths to which foundation footings have 1. It can be left open and used for such things to be set or piles driven depend on local soil con- as parking and boat storage. ditions, frost penetration levels, flood loads, and 2. It can be enclosed with breakaway panels anticipated scour. These all affect the cost of or knock-out walls that will collapse construction, and can cause variation from the under hydrostatic pressure without dis- cost estimates presented here. turbing the structural support of the building (see Figures 2-6 through 2-9). Recommended usage of this area would be temporary storage and garage space. STAIRS AND UTILITIES 3. Basements are generally prohibited in residential structures that are located in Elevating a residence may result in increased cost flood hazard areas. Under extraordinary for stairs and for utilities that must be brought circumstances, where their omission would from grade. These costs were not considered in cause severe hardship and gross inequity, the estimates presented here since they may vary the Fede'ral Insurance Administrator may with height of elevation, cost assignment, i.e. grant an exception to permit basements. who pays for installation, and elevation method. 4-5 THE REAL COST OF ELEVATING A annual average flood damage that the owner of RESIDENCE the example house could expect (see Table 4-3). The economic cost to the individual of building a home in the flood plain consists of both flood damages that will occur and the costs of what- TABLE 4-2 ever measures are taken to mitigate such Estimates of Flood Damage damages. The cost of flood damages to the to a $25,000 1500 Square-Foot Home with homeowner may be partially shifted to Federal, No Basement With Contents state and local government through low- Valued at $12,500 interest loans and tax deductions for losses in- Depth of Water Probable curred. The Red Cross and other agencies also Above First Damage to Damage to Total Value reduce the cost of flood losses to individuals Habitable Floor Structure Contents of Damage through theirdisaster assistance programs. In O Ft. 7% $1,750 10% $1,250 $ 3,000 communities participating in the National + 1 Ft. 10% 2,500 17% $2,125 4,625 + 2 Ft. 14% 3,500 23% 2,875 6,375 Flood Insurance Program, the owner of a new + 3 Ft. 26% 6,500 29% 3,625 10,125 home may purchase flood insurance at + 4 Ft. 28% 7,000 35% 4,375 11,375 + 5 Ft. 29% 7,250 40% 5,000 12,250 actuarial rates which reflect the degree of risk. +6 Ft. 41% 10,250 45% 5,625 15,875 Essentially, flood insurance allows the homeowner to spread the flood risk to others facing the same hazards, and more importantly permits one to pay for expected flood losses Table 4-4 illustrates the options which are which are unpredictable with respect to size available to an individual wishing to construct a and time of occurrence in predictable annual new, $25,000 one-story home with no basement payments. These are more manageable than in Zone A-8 where the original ground is six feet unexpected flood losses, especially if more below the base flood elevation. It should be than one large flood happens to occur in a very noted that under FIA regulations a home could short time. not be constructed with the first floor below the base flood level unless a variance has been A prospective homebuyer could reduce his granted by the community where the house is susceptibility to damage (and flood insurance to be located; however, this example is useful premiums) by floodproofing. There are many to illustrate the economic advantage of forms of floodproofing; however, this elevating. discussion will deal only with elevation. Generally the least expensive means of As shown in Table 4-3, at this location the obtaining 2 or 3 feet of elevation is with fill. For house would receive $1,500 in average annual greater elevation, posts, piles, or piers would damages if constructed on a slab-on-grade, be the best choice. Figure 4-4 illustrates this which is option A in Table 4-4. In this case the relationship. cost of flood insurance is approximately equal to the expected damages. Options B, C, and D Tables 4-2 through 4-4 present the cost picture are ways of reducing the net cost to the in terms of the 1500 square foot one-story homeowner of occupying the flood plain. house being used for estimating purposes in Option B is to elevate on fill, and options C and this section. The data presented in these three D are to elevate using columns. For purposes of tables is for a particular flood plain in Louisiana comparison all costs in Table 4-4 were put on and would likely be different on other flood an annual basis, thus the initial cost of eleva- plains. tion which would normally be included in the mortgage is shown as the additional yearly cost Table 4-2 indicates the extent of damages that a which would result in the mortgage payments. $25,000 structure with $12,500 worth of con- This example also shows the relatively small tents would sufer from particular depths of impact of elevating on the monthly cost of the flooding. The probability for each depth of home, for example option D would result in a flooding was used to refine the flood damage $22 per month increase in the mortgage data in Table 4-2 into figures for the probable payment. 4-6 These tables show that for this home it would TABLE 4-3 be less expensive to elevate to or above the Average Annual Damage base flood level than to build below it and Floor Elevation Probable Average suffer loss. Above Grade Annual Damage 0 Ft. $1550 +2 625 +4 160 +6 50 TABLE 4-4 Economics of Elevation fora $25,000, One-Story, No Basement House in Zone A8 Option D Flood Insur. Premium Option $103 Base Flood Elevation 0 feet C Flood Insur. Cost of j~ 1~ Premium Columns ~ ] ~$308 $2,458 Option Expected Average Annual -2 feet B Flood Insur. Cost of /I / Premium Columns $790 $2,246 Option Damages at this site-$1550 -4 feet A Flood Insur. Cost of Fill Premium $1,470 $1503 Original Ground -6 feet ANNUAL COSTS A B C D Annual Flood Insurance Premium $1503 $ 790 $ 308 $ 103 Additional Annual Cost of Elevation (30 yrs at 9%) 156 240 261 Total $1503 $ 946 $ 548 $ 364 Average Annual Damages Expected 1550 1550 1550 1550 Net Annual Savings by Purchasing Insurance and $ 47 $ 604 $1002 $1186 Clearly the probabilities indicate that the out-distance increased foundation costs overall savings achieved by employing elevated especially when considered in the perspective foundations at least to the level of the base of the total cost of the structure. flood when constructing in the flood plain far 4-7 ESTIMATING ELEVATED FOUNDATION COSTS The costs of post, pile, and pier foundations are sented in the graph are for a 1624 square foot compared to each other and to the costs of con- house on the Amite River in East Baton Rouge ventional slab, crawl space, and basement Parish, Louisiana. It is important to note, from foundations in this section of the manual. Cost this graph, the relative costs of foundation types data and estimating forms are provided for and that increasing the floor elevation increases roughly estimating one's particular foundation costs at a substantial rate only in the case of the costs. fill option. The most economical type of foun- dation for elevating a residence will vary with The elevated foundation types reviewed here the height of elevation. Table 4-5 relationships should not necessarily be construed as the best are specifically for Louisiana; however, the rela- or most economical means of elevating resi- tionships should be similar throughout the dences: They are presented because they are nation. currently the most common means. Cost is not the only determinant for selecting the material and method for elevating. Other considerations, including market acceptance ELEVATION COST DIFFERENCES (buyers and banks), architectural design integra- tion, climatic conditions, site conditions, and Table 4-5 graphically compares the cost of con- anticipated flood hazards should also be structing seven types of foundations at various considered. elevations. The foundation alternatives pre- TABLE 4-5 Cost Comparison of Foundation Types for a Specific House in Louisiana i i I : ' 12 j 1 I 1 1- -KEY ,, = Conventional Slab-on-Grade . = Slab +-Site Fill o o o = Concrete Piling � * **= Brick Piers ~. 9-------..* = Wood Piling n3= 6 x 6 Posts .� � .= 8x 8 Posts [] (a � _,a,0 00')O"- -J~~~~~~~~~~ 7 0 7 6 co6 o5 0 0a I4. (3 [ CI, o~~~~ 2 1 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 ELEVATION IN FEET 4-8 -16Bioood .00-.otOo~a 1' .0 S.,ed S.Wilt ~ ~ 4 m l 2oIa-01 k-TI ~ ~ ~~~~~~2.100. - 12 ft. 24"~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~1 Di. I" .C. FOUNDATION SECTION FOUNDATION PLAN ELEVATED WOOD POST FOUNDATION $3035 per square foot 2 p lilL., OotO0oetO 0 P lp" Ri,. 00G.001 "6 Datla \/P16tt loc R0c~t 6000aBl. 01'~~~~~~~~~~~~~~~~~~~~~1 ELEVATED~~~~~~~~~~~~~~~~~~~~~~~~~~ WOO PI iLFOUNDThION~ 3.5pr sqar fo DI~~~~~~~~~~~~~~~bl. ~ ~ ~ ~ ~ ~ ~ 60 24-1" Guid., ~ ~ ~ FUNATO SETIOONAINPA ELEVATED~~~~~'I COCEEPEPOUDTOI-a9 e qaefo 4.9~~~~~~~~~~~~~~~~~0-1 SLAB-ON-GRADE CONSTRUCTION vs. ELEVATED FOUNDATIONS Use this page for cost estimating if the houses 4 ,"r/-illpl. / "COnC.l. built in your area have foundation systems ....... : _ m .-....... similar to the illustration at the right. D CInd .,Rod Ga-eI ... ... . .. .... .FOUNDATION SECTION - 2'-0 24 -0" FOUNDATION PLAN SLAB-ON-GRADE $1.27 per square foot 1. Since the foundation and floor slab of a conventional house represent about 8% of the total cost of that house (not including land), the effect of elevating by one of the three techniques shown in Figure 4-3 on the total price of the house is relatively modest. -10% 0% +10% +20% Impact on Total cost of house POST III1IIIIIIIIIII1111111111111111111 + 14% PILE lii1lIIIIIIlIll111111111111111 + 12% PIER II111111111111I1111111IIIIIIIIIII + 15% IMPACT OF COST ON WHOLE HOUSE 2. Figure 4-3 illustrates three practical methods of elevating house so that their first floors are above the base flood level. The relative cost of each per one hundred dollars as compared with the cost of conventional slab-on-grade construction is shown on the following bar graph. For example, the cost of a 1500 square foot slab- on-grade foundation would be $1905, based on a cost of $1.27 per square foot. A comparable wood post foundation would cost a total of $5029, with a pile founda- tion being less expensive and a pier foundation being more expensive. 0 100 200 300 400 Cost Per $100 SLAB IIIIIIillllll lll $1.00 POST IIIIUMIIIhIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII $2.64 PILE IIll11I11111I1111111I IIIIIIIIIIIIIIIIII $2.40 PIER $2.83 PIER !11111 1111111111111111111111111 11111111111111111111 1 $2.83 IMPACT OF COST ON FOUNDATION/DECK ONLY 4-10 W-Plywod Otok , -9.10 J~i.. I W D.C. SIk. G,,d~ ~ ~ ~ ~~AL Sbl2.10 ITG D.-.TtLULU-.co -2 ft2 r..d ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ - j0W...SiMill0 0 DC 26-0 241- FOUNDATION SECTION UNAINPN ELEVATED WOOD POST FOUNDATION $ 3.35 per square foot ftPly-d D- 10. W DC 2,11 ~~L Id~ 1 P~~~~~~~~~~~~~~~F 'zjpfD j...] ~ I.~~~~~~~~~~~~~~~~~~~~2 P- - - IT4T-0 ELEVATED WOOD PILE FOUNDATION $305 per square footd PI1.--. 1 PVOO~~~~~~~~~~~~~~~~~~dS~~~~~~~~~~~k~~L I! Bat ItO. I V E~~~~~~t Pyvacodl l S L _L21te ft2 N.Dc ot ~~ ~~~ c- a 51.4 An5. I~~~~~~~~~~~6'O"24 .1 -I 0~~~~~~~~ FOUNDATION SECTION FOUNDATION PLAN ELEVATED WOODET PILER FOUNDATION $ 3.059 per square foot D-1. 2.1 2 ~ ~ ~ 4-1 CRAWL SPACE CONSTRUCTION vs. ELEVATED FOUNDATIONS Use this page for cost estimating if the houses 2.OH I 'PID built in your area have foundation systems Ebd - _M. similar to the illustration at the right. 26I pll- PI-3-2x 4 x x16 Cap., BlTBock F---i ED I _ I _ _, , di8X1C~loek 0tt7 At 4 v V Pis j[,o p 3-o2,l.e ,l :,o. Xo.-o. B apo , , 1 X D._ .... 9....' -0" ___ FOUNDATION SECTION FOUNDATION PLAN CRAWL SPACE $1.95 per square foot 1. Since the foundation and deck of a conventional house represent about 12% of the total cost of that house (not including land), the effect of elevating by one of the three techniques shown in Figure 4-3 on the total price of the house is only: -10% 0% +10% +20% POST lo 9% PIE IIIIIIIIIIIIIIIIIIIII 10% PIER lillllllllllll1111111 10% IMPACT OF COST ON WHOLE HOUSE 2. Figure 4-3 illustrates three practical methods of elevating houses so that their first floors are above the base flood level. The relative cost of each per one hundred dollars as compared with the cost of conventional crawl space construction is shown on the following bar graph. For example, the cost of a 1500 square foot crawl space foundation would be $2925, based on a cost of $1.95 per square foot. A comparable wood post foundation would cost a total of $5031, with a pile founda- tion being somewhat less expensive and a pier foundation slightly more expensive. o 100 200 300 400 Cost per $100 $1.00 CRAWL ii11IIIl111111 POST lllllllllllllll$1.72 PI LE IIIIlIIIIIIIIIIIfihIIIlll $1.56 PIER IIIIIIIIlIlIlIlIIII1111111111111 $1.84 IMPACT OF COST ON FOUNDATION/DECK ONLY 4-12 6Battln~~~~~~~~~~~~~~~~~~~o~1 D'Et.lyO T.~~~~~~~~~~~~~~~~~~~~~~~~~~~~~00 C_4~ ~ ~~~~~~~~~'D. a.Blso~l~~2'~~T14 'i! ~~II o0Jit 'pi" ~~~~~~~~~~~~~~~Gd, ,W, Di. G- 0'00 r-p-E,~~~~~�K Gwd I 2.F12.~l I ii r III~~~II~tIII~~tII~t1 Sp~~~~~~~~~~os~~~~~~ Grdso- 1 20 R.'-- - Pd~~~~~~~~~~~Wo P.st-60 ~~~~,Ik. ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ I 36d 2.01' G-10 Fl. 8~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~nta Sat n 000 SO~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~1I, 1e Oif .1 0o~~~~~bo~~~~o raps~ ~ ~ ~ ~ ~ ~~~~~~~~~~~~~~~o1~~~~~~~~~~~~~~~~~~~~~~~~1 1 soya, F~~~~~~~~~~~~~~~~~~~~~~~~~~~~~. FOUNDATION SECTION FrOUNATIN PLAr-Ni Gvd-000_ S.]A i 174, 7-1 ~ ~ ~ -1 BASEMENT CONSTRUCTION vs. ELEVATED FOUNDATIONS Use this page for cost estimating if the houses 2.. H.e.r. -1I I built in your area have foundation systems ._2oJ._. similar to the illustration at the right. .S......... . . ~m ............. 2.10 .1.. 'G. . -T[I P1.rA T.t S.I Welded 8idtl SeCap Block Co n .....d Legge. TN/.etebsmntfu. $xl8lk 8,tprFdn 4" to6 8" Crred W _12 81oE en Coueh- 3" Die. Steal Col. Over, rain Tile _ 2',I2 Sase F' Jotstzd16" p C T a Plate TGa Weld to m te--PI/ Welded 2ldsrlo.-i4-u-ar 3 CoI & Fooin L 20 l & Sti -eforng j1 L Ti i - -l a 50'-"' X POST t resd t o ne PIER lol l 1i IMPFOUNDATIOF COST ON WHOLE HOUSE 2. FiguNDATON 4-3 illustratAN BASEesENT $3.49 per square foot . Sincareabove the base flood levelnt foundation and deck of each pconventional houserepresentabout 20% of the total cost of that house (not including land), the effect of elevating by one of the three tefollow n ing bar Figure 4-3 on the t o ta l price of the house is: -10% 0% +10% +20% POST 111111111111111 $.96 - 1% PILE 1111111111111 $ .87 - 13% PIER 11111111111111 $1.03 + 13% IMPACT OF C OST ON WHOL E HOUSE 2. Figure 4-3 illustrates three practical methods of elevating houses so that their first floors are above the base flood level. The relative cost of each per one hundred dollars as compar ed with the cost of conventional basement construction is shown on the following bar graph. For example the cost of a 1500 square foot basement fo undation would be $5235, based on a cost of $3.49 per square foot. A comp arable wo od post fo undation wo uld cost 4% less, or a total of $5025. 0 100 200 300 400 BASEMENT !!111Ui!1111111I1 $1.00 POST !1111HiIhl $.96 - 4% PILE IIIIIIEIII $ .87 - 13% PIER !111111111111111111 $1.03 + 3% IMPACT OF COST ON FOUNDA TION/DECK ONLY NOTE: When comparing basements to elevated foundations the reader may want to allow for lost potential basement storage space. If this is the case, the reader may allow an added cost for the 300 to 900 cubic feet of storage space that is lost. Considering that basement storage is generally dead storage, the reader may add a square foot cost (appropriate to his area) for an additional 50 to 150 square feet of storage space. 4-14 FUTURE FACTOR Proportional Relationship: 1:1.05:1.68 Building costs are difficult to get a long term The following blank format is for computing the handle on because of the tendency for the cost current relationship: of basic construction commodities, lumber, con- crete, and steel, to fluctuate and to vary relative Date for BLSWPI: to each other (see Figure 4-1). This section attempts to show the interested reader how to Steel: ( = 1 adjust the cost data presented in this manual for those cost variations. These adjustments will Concrete: ( provide a rough current idea of how the cost of the various methods of elevating compare. Esti- Lumber: ( )/( ) = mating sheets are provided at the end of this section for determining exact costs. Proportional Relationship: 1: _: PERCENTAGE COST COMPARISONS1 SQUARE FOOT COSTS' The percentage cost comparisons made in the fouperendatin cost comparison.smdetin shobe .The square foot costs stated in this manual can foundation cost comparison section should be ...alidowhenever t h areisuton usection th basic be adjusted, in approximate terms, for price vari- valid whenever they are put to use if the basic ations by multiplying the square foot cost by an construction commodities are in approximately adjustment factor. This Adjustment Factor the same proportional relationship to each other (AF) is determined by dividing the current I as they were in the Spring of 1974. At that time for the predominant foundation material by its the Wholesale Price Index (WPI) for structural for th e predomin ant foundation material by its steel was 127.3; for ready mix concrete, 133.3; and for softwood lumber, 214.3. EXAMPLE: The year is 1976. You want to The current Wholesale Price Index for each of know the current square foot cost for an ele- the construction commodities can be obtained vated wood pile foundation. The predominant from the Bureau of Labor Statistics (BLS) of the material is wood with a 1974 WPI of 214.3 and Department of Labor in Washington, D.C. The a 1976 WPI of 244.5. The 1974 square foot following computational format shows one way cost is $3.05, therefore: to make the proportional comparison to see if current prices still have the Spring, 1974 rela- tionships: = (244.5)/(214.3) = 1.14 Date for BLSWPI: Current Square Foot Cost = (AF) x (1974 cost) = (1.14) x ($3.05) =$3.48 Steel: (Steel)/(Steel) = 1$3.48 Concrete: (Concrete)/(Steel) = LOCAL ESTIMATING GUIDELINES Lumber: (Lumber)/(Steel) = In order to confirm cost differences in your area Proportional Relationship: 1: : cost worksheets are provided for the types of foundations shown in this analysis. These work- Spring, 1974 computations: sheets begin on the next page. Date for BLSWPI: Spring, 1974 Steel: 127.3/127.3 = 1 1. Material ordinarily comprises 60% of the cost of a dwelling. The Bureau of Labor Statistics Wholesale Price Index is for Concrete: 133.3/127.3 = 1.05 materials only. When making a rough estimate by ratio com- parison using materials only a small error will develop since labor will be raised by the materials cost. This error is not too Lumber: 214.3/127.3 = 1.68 significant for rough estimating: 4-15 I ESTIMATING FORMS Ar~~~~~~~~~ ~4-17 - ~~~4-17 SLAB-ON-GRADE ESTIMATING FORM TO DETERMINE LOCAL COSTS Compute the following and enter: Square Footage of Floor Area Lineal Footage of Perimeter Square Footage of Foundation Wall Enter you costs (combine labor and material) and extend: Layout house on lot = $ Trench for footing x LF = $ Place footings x LF = $ Lay-up or form & pour foundation wall x SF =$ Fill & grade for slab x SF = $ Place vapor barrier, wire mesh & insulation x SF = $ Place & finish slab x SF = $ Grand Total $ 4-19 CRAWL SPACE ESTIMATING FORM TO DETERMINE LOCAL COSTS Compute the following and enter: Square Footage of Floor Area Lineal Footage of Perimeter Square Footage of Foundation Wall Number of Piers Enter your costs (combine labor and material) and extend: Layout house on lot = $ Trench for footing x LF = $ Place footings x LF =$ Lay-up or form and pour foundation wall x SF = $ Place pier footings x Ea. = $ Lay-up or form and pour piers x Ea. = $ Backfill x CY = $ Floor Girder x LF = $ Floor Framing x SF =$ Insulation & sealer x SF = $ Subfloor x _ SF = $ Place floor slab x SF = $ Grand Total $ 4-20 BASEMENT ESTIMATING FORM TO DETERMINE LOCAL COSTS Compute the following and enter: Square Footage of Floor Area Lineal Footage of Perimeter Square Footage of Basement Wall Area Number of Basement Support Columns Enter your costs (combine labor and materials) and extend: Layout house on lot = $ Excavation & spoil removal x SF = $ Place footings x LF = $ Place pier footings x Ea. = $ Lay-up or form & pour foundation wall x SF =$ Parge wall x SF = $ Set drain tile x LF = $ Backfill x CY = $ Place vapor barrier and wire mesh x SF =$ Place and finish floor slab x SF =$ Place girder x LF = $ Frame Floor x SF = $ Place subfloor x SF = S Grand Total $ 4-21 WOOD POST ESTIMATING FORM TO DETERMINE LOCAL COSTS Compute the following and enter: Square Footage of Floor Area Lineal Footage of Girders Number of Posts Enter your costs (combine labor and material) and extend: Layout house of lot = $ Auger or dig post holes and remove spoil x Qty = $ Place concrete punching pad x Qty = $ Place poles x Qty = $ Backfill poles and plumb x Qty = $ Set girder x L F = $ Frame floor x SF = $ Place insulation & sealer x SF = $ Place subfloor x SF = $ Grand Total $ 4-22 WOOD PILE ESTIMATING FORM TO DETERMINE LOCAL COSTS Compute the following and enter: Square Footage of Floor Area Lineal Footage of Girders Number of Piles Total Lineal Footage of Piles Enter your costs (combine labor and material) and extend: Layout house on lot = $ Bring pile-driving equip- ment to site X = $ Furnish and drive piles x . LF = $ Set girder x LF = $ Frame floor x SF = $ Place insulation and sealer x SF = $ Place subfloor x SF = $ Grand Total $ 4-23 CONCRETE PIER ESTIMATING FORM TO DETERMINE LOCAL COSTS Compute the following and enter: Square Footage of Floor Area Lineal Footage of Girder Number of Piers Enter you costs (combine labor and material) and extend: Layout house on lot = $ Auger or dig pier holes and remove spoil x Qty = $ Place concrete footing x Qty = $ Form & pour piers x Qty = $ Backfill x Qty = $ Set girder x LF = $ Frame floor x SF = $ Place insulation and sealer x SF = $ Place subfloor x SF = $ Grand Total $ 4-24 ~~~~~~~~~~~~~~~~~~~~~I Appendix i -_~~. ... I" -I LOCAL SOURCES FOR FLOOD DATA COMMUNITY INFORMATION SOURCES STATE WATER RESOURCES AND FLOOD PLAIN MA NAGEMENT AGENCIES - Most To achieve useful results the general guidance states have agencies under various titles that deal provided in this manual must be combined with with water-related problems. They may provide specific information relating to the local corn- valuable information for dealing with flood re- munity. Those concerned with local flood con- lated problems. ditions will want answers to such questions as, "Where is the flood plain boundary?" and EXPLANA TORY NOTES- Some of the pre- "What is the base flood elevation above ceding information items deserve a word of fur- mean sea level?" (i.e., required elevation of the ther explanation. lowest floor) and "How do the local land eleva- tions relate to the base flood level?" The 1. Flood Hazard Boundary map (FHBM)- answers to these and other similar questions are This map approximately identifies those different for each community but should be areas within a community subject to inun- answerable through one or more of the follow- dation by the base flood and therefore sub- ing sources: ject to flood plain regulation. Owners re- questing financial assistance from Federal LOCAL GOVERNMENT - Some or all of the or federally regulated or insured financial following information on the community flood institutions for construction or substantial hazard areas should be available from the local renovation of structures within a special building official: flood hazard area are required to obtain 1 ) Flood Hazard Boundary Map (FHBM), flood insurance as a pre-requisite to such 2) Zoning Code, financial assistance. Similarly, in issuing 3) Building Code (local, county or state), building permits, communities must en- 4) Subdivision Regulations, force flood plain regulations in these areas 5) Flood Plain Ordinances and Resolutions using the best information available with (local or state). regard to the base flood elevation. The Flood Insurance Rate Map (FIRM) and the FIA FLOOD INSURANCE RATE MAP (FIRM) information it contains supersedes the - If it is not contained in the foregoing legal FHBM when it becomes available, and in instruments the following information will be all cases, the latest information of addi- available on the FIA Flood Insurance Rate Map: tions to a FIRM should be consulted. (See 6) Elevation of the base flood, examples of FHBMs and FIRMs on the 7) Elevation reference marks and bench following pages.) marks (on maps issued after July, 1975) 8) Identification of velocity zones and 2. Zoning-The flood plain management coastal high hazard areas. regulations a community adopts when it becomes a participant in the National Flood Insurance Rate Maps should be on file, to- Flood Insurance Program are frequently gether with the Flood Hazard Boundary Map, at incorporated into the community's zoning the local building official's office once the code. Zoning restrictions generally specify maps have been received. how land may be developed, its carrying FEDERAL WATER RESOURCE AGENCIES- capacity, and what kinds of uses are The following information is not usually found acceptable. According to FIA's Flood in local or state codes and regulations and is not Hazard Boundary Map a special flood found on rate maps but may be available from hazard district or zone is created and the Federal agencies involved in water resources regulations controlling flood plain manage- management ment specifically apply to this flood 9) Riverine velocities and coastal surges. hazard zone. 5-3 LEGEND SPECIAL FLOOD HAZARD AREA WITH ZONE A i t!!l DATE OF IDENTIFICATION DATE 01 02 / AreaC O lhe Ion.ruNa � After amo r e dated study te Fl// Iparl FioYd Haoard Ara rhown on /hr/a mrap ma, /e % r~~~~~~~~~~~~~modlted 8ad oSh, ,rea added CONSULT NFIA SERVICING COMPANY OR LOCAL INSURANCE DEPAGENT OR HAOUER BRO ETERMINE IF PROPERTIES IN THIS COMMUNITY ARE ELIGIBLE FOR FLOOD INSURANCE. ~~~~RIIL~~~~ro~~~~~~~ II~ ~INITIAL IDENTIFICATION DATE: AUGUST 9, 1974 rtosor WATER ST IsHO CaII tI'E 6OUaOaIr� RO S-ft, Pd;.tI' _IOu:t sral. / "0 04 FDIC,, / O~~~~~~~~~~~~DEPARTMENT OF HOUSING AND URBAN DEVELOPMENT ~~~~~i~~~~~~~~~~~~~~ ~~~~~~~Federal Imurance Administration FLOOD HAZARD BOUNDARY MAP H 01-04 NAME OF COMMUNITY COMMUNITY NO 250300A AR- ' XONE~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~oO ' 8~~~~~~~6/761 /�~~E~[ ZONEA Zo~JEA4~4q8 9 F-4 - 0~~~~~~~~~~~~~~~~~~- ZONE mkZE .86,76, c Ga!3 C LO~LSTI~ - ~~~~~~~~~~~~~~~~ ZONE A~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~7 C-D 6~~~~~~~~~~~ ~~~~~~~~~~~~~ /' 76A ~~ *~~~04 ,/"$ - / ~~~~~~~~~~~~JOINS 04 0 KEY TO SYMBOLS ZONE B ZONE DESIGNATIONS' WITH OATE OF IOENTIFICATION 'ho. ZONE B A~~~~~~~sr B lod Elevtnon oL, Bs- Flood Elnooton (513' MSL; Ei..N..n Rfid.-ns M.,k RM7X REm Vil. -M1.5 -EXPLANATION OF ZONE DESIGNATIONS *\ flood ioeoueoo oiuo dietteye tnt too dmioOutio Ort f 008 ii oouording to oesoo of di~nioeod flood Iio1oidt.ro Te ut dmignetiofl 00Yh FIA A00 lii LAGUNA A Al. .1 -s.. f- -.1. (SF1) %t%4 MADRE boec food -l-tlooa eoioed. Atf Looooofu~lA3A Al-otiti floo hoodidt (SF01 -- ith tote flood Z- ltfot. Zoom Z ot mojone 000000.0 00 flood fod fE<lt. hod d .I-ef SF0 id-OliOfi- .(n~~~~~~~~~~~~~~~~~~~~~~~~~~~~. *0 Wit Ofu Lo ctil flood f�It�edo 0000 0000 thDIloo Cl,04(rod d~otoo lli mmo 00000 eflo',ooor ugtdioo- SATE ROUTE dtAt0,o0 V A.-eof ee.ll .004 iiuede. With - oeoo;O ff00 er� iOOnd~fed SR fidel flood.. Zoos to. ta.00 ei-oridi )t to lood 0.00,4 fefloti hod doom of SF0 id-IIII-Ii..o A I 0 ~rrl 11 1111drd� o died dO 000d000000id. hot Po00 hoe flood ho~ddid CONSULT NFIA SERVICING COMPANY OR LOCAL INSURANCE AGENT OR BROKER TO DETERMINE IF PROPERTIES IN THIS COMMUNITY ARE ELIGIBLE FOR FLOOD INSURANCE. INITIAL IDENTIFICATION DATE: JULY 21.1972 INTERIM MAP REVISION EFFECTIVE JULY 1.1974 TO CHANGE ZONE DESIGNATIONS MAP REVISION EFFECTIVE JULY if. 1975 TO REFLECTCURVILINEARFLOODBOUNOARY ADDITIONAL MAP REVISION EFFECTIVE JUNE 11. 1976 TO CHANGE SUFFIX AND ADD SFHA DEPARTMENT OF HOUSING AND URBAN DEVELOPMENT Fedmli Insurancs AdIiniUsIrtion FLOOD HAZARD BOUNDARY MAP H -01 FLOOD INSURANCE RATE MAP I -01 MAP INDEX NAME OF COMMUNITY COMMUNITY NDO 485483C 0 r. - 0 I~~~~ ( - Ca-9 1 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~CD CC =Cm 0C LL.1 3. Building Code (Local, County or State) B - Area between Zone A or V and the -Sometimes those flood plain regula- limits of the 500-year flood, tions that prescribe construction practices and floodproofing techniques are placed in or the Building Code. In addition, the Build- ing Code should be consulted for locally Area that is protected from a base allowable soil bearing pressure required, flood by a dike, levee, or other com- safety factors, permit requirements, pleted water control structure. anchoring requirements, etc. C-Area subject to flooding by the 4. Subdivision Regulations - Sometimes greater than 500-year flood, special flood plain regulations, such as requirements for floodproofing of utilities, or elevations of roads, grading and drainage requirements, lot sizes, etc., are found in Area that is protected from the Subdivision R~egu lations. greater than 500-year flood by a dike, levee, or other water control 5. Flood Plain Ordinance and Resolutions structure. (Local or State) - In some cases all require- Elevations indicated on FIRM may be de- ments regarding land use and construction termined in the field through elevation re- in the flood plain are brought together in a ference marks. Locations and descriptions single flood plain ordinance. of these bench marks or reference marks are generally included on the FIA Flood 6, 7, 8. Surface Elevations of the Base Flood, Insurance Rate Map. If not shown on the Elevation of Bench Marks, and Identifica- FIRM, bench marks or elevation tion of Velocity Zones-The surface ele- reference marks must be obtained from vation of the base flood determines the the local building official or from the level at which the finished floor of the contractor or agency who prepared the of the lowest habitable floor of a building FIRM. must be designed. The FIA Flood Insur- ance Rate Map divides the community into 9. Riverine Velocities and Coastal Surges - flood hazard zones and gives the base Estimated velocity data are generally avail- flood elevations for each zone. Zones are able from local offices of Federal Agencies indicated as follows: involved in water resources. Al through A30 - Special Flood Hazard areas inundated by the base flood with base flood elevations and zones LEGISLATIVE DATA assigned according to FHF (Flood Hazard Factor) As a condition of future federally-related financ- ing, all communities in identified flood hazard AO-Special Flood Hazard areas inundated areas are required to participate in the National by the base flood with shallow Flood Insurance Program and to adopt adequate flood depths and/or unpredictable flood plain ordinances with effective enforce- flow paths. Base flood elevations ment provisions consistent with Federal stan- are not determined. dards to reduce or avoid future flood losses. The specific details and requirements for partici- V1 through V30 - Special Flood Hazard pation are spelled out in the National Flood areas inundated by the base flood Disaster Protection Act of 1973 (PL 93-234) with additional hazards due to velo- and Title-24 from the Code of Federal Regula- city with base flood elevations and tions. These are essential readings for those and zones assigned according to FHF planning flood plain regulation or flood plain (coastal areas). construction. They may be obtained by writing: 5-8 CONCLUDING COMMENTS Federal Insurance Administration Investigation of the information sources reviewed Department of Housing and Urban above should provide designers, builders, bankers, Development community officials, and the general public with the 451 7th Street, S.W. appropriate information fpr prudent management, Washington, D.C. 20410 planning and construction in the flood plain. Specific flood insurance questions should be addressed to the Flood Insurance Specialist in your HUD Regional Office (see listing below). REGION I REGION VI New Federal Building Room 800 1 100 Commerce Street John F. Kennedy Building Dallas, Texas 75242 Boston, Massachusetts 02203 (214).749-7412 (617) 223-2616 [includes Arkansas, Louisiana, New [includes Connecticut, Maine, Mexico, Oklahoma, Texas] Massachusetts, New Hampshire, Rhode Island, Vermont] REGION VI I REGION II Federal Office Building 911 Walnut Street 26 Federal Plaza Kansas City, Missouri 64106 New York, New York 10007 (816) 374-2161 (212) 264-4756 [includes Iowa, Kansas, Missouri, [includes Nelk Jersey, New York, Nebraska] Puerto Rico, Virgin Islands] REGION Vill REGION III Federal Building Curtis Building 1405 Curtis Street 5Sixth and Walnut Streets Executive Tower, 27th Floor Philadelphia, Pennsylvania 19106 Denver, Colorado 80202 (215) 597-9581 (303) 837-2347 [includes Delaware, District of [includes Colorado, Montana, North Columbia, Maryland, Pennsylvania, Dakota, South Dakota, Utah, Wyoming] Virginia, West Virginia] REGION IX REGION IV 450 Golden Gate Avenue 1371 Peachtree Street, N.E. Post Office Box 36003 Atlanta, Georgia 30309 San Francisco, California 94102 (404) 526-2391 (415) 556-3543 [includes Alabama, Florida, Georgia, [includes Arizona, California, Hawaii, Kentucky, Mississippi, North Nevada] Carolina, South Carolina and Tennessee] REGION X REGION V Room 3068 Arcade Plaza Building 1321 Second Avenue 300 South Wacker Drive Seattle, Washington 981 01 Chicago, Illinois 60606 (206) 442-1 026 (312) 353-0757 [includes Alaska, Idaho, Oregon, Washington] [includes Illinois, Indiana, Michigan, Minnesota, Ohio, Wisconsin] GLOSSARY ACTUARIAL RATE ZONE-A zone identified on a EXISTING CONSTRUCTION--For the purposes of Flood Insurance Rate Map (FIRM) as subject to determining rates, means those structures in a specified degree of flood, mudslide (i.e., existence or on which construction or substan- mudflow) or flood-related erosion hazards, to tial improvement was started on or before which a particular set of actuarial rates applies. December 31, 1974, or the effective date of the Flood Insurance Rate Map (FIRM), whichever is BASE FLOOD-Sometimes referred to as 100 year later. For the purposes of flood plain manage- flood, is a flood of the magnitude that has a 1% ment regulations requirements, existing con- chance of occurring in any given year. struction means those structures in existence or on which construction or substantial im- COMMUNITY-Any state or areas or political sub- provement was started prior to the efective date division thereof, or any Indian tribe or autho- of a flood plain management regulation rized tribal organization, for which an applica- adopted by a community. "Existing construc- tion for participation in the National Flood tion" may also be referred to as "existing Insurance Program is made, and which has the structures." authority to adopt and enforce flood plain management regulations for the areas within its FLOOD OR FLOODING-A general and temporary jurisdiction. condition of partial or complete inundation of normally dry land areas from the overflow of COASTAL HIGH HAZARD AREA (CHHA)-The inland or tidal waters, or from the unusual and portion of a coastal flood plain having special rapid accumulation or runoff of surface waters flood hazards that is subject to high velocity from any source, or from mudslides, which are waters, including hurricane wave wash and precipitated by accumulations of water on or tsunamis. under the ground, or from the collapse or subsi- dence of land along a shore of a body of water DEDUCTIBLE-The fixed amount of percentage of as a result of flood-related erosion. any loss not covered by insurance. The total loss must exceed this amount before any insur- FLOODPROOFING-Any combination of structural ance claim may be paid. and nonstructural additions, changes, or ad- justments to properties and structures which EMERGENCY PROGRAM-The program which is reduce or eliminate flood damage to lands, initiated before the individual community rate- water and sanitary facilities, structures, and making studies. It is intended as a program to contents of buildings. provide a first layer amount of insurance at federally-subsidized rates on all existing struc- FLOODWA Y-The channel of a river or other water- tures and new construction begun prior to the course and the adjacent land areas required to effective date of a Flood Insurance Rate Map, in carry and discharge the base flood without return for the community's adoption of general cumulatively increasing the water-surface flood plain management regulations. elevation more than one foot at any point. EROSION-The collapse or subsidence of land FLOOD ELEVA TION STUDY OR FLOOD along the shore of a lake or other body of water INSURANCE STUDY-A scientific examination, as a result of undermining caused by waves or evaluation and determination of flood hazards currents of water exceeding anticipated cyclical and corresponding water surface elevations, or levels or suddenly caused by an unusually high a scientific examination, evaluation and deter- water level in a natural body of water, accom- mination of mudslide (i.e., mudflow) and/or panied by a severe storm, or by an unantici- flood-related erosion hazards. patea force of nature, such as a flash flood or an abnormal tidal surge, or by some similarly FLOOD HAZARD BOUNDARY MAP-An official unusual and unforeseeable event which results map or plat of a community issued by the FIA in flooding. Therefore, the use of the word on which the boundaries of the flood plain, "erosion" shall mean flood-related erosion. mudslide and/or flood-related erosion areas having special hazards have been drawn. 5-10 FLOOD INSURANCE RATE MAP-An official map MUDSLIDE (i.e. mudflow)-A condition where there of a community on which the FIA has delin- is actually a river, flow or inundation of liquid eated the area in which flood insurance may be mud down a hillside usually as a result of a dual required under the Regular Flood Insurance condition of loss of brush and the subsequent Program and the actuarial rate zones applicable accumulation of water on or under the ground to such area. These maps also provide base (frequently caused by a period of heavy or sus- flood elevations and, in coastal communities, tained rain.) A mudslide may occur as a distinct the velocity zones. phenomenon while a landslide is in progress and will be recognized as such by the FIA only FLOOD PLAIN OR FLOOD PRONE AREA -The land if the mudflow, and not the landslide, is the area adjoining a river, stream, watercourse, proximate cause of the damage that occurs. ocean, bay or lake Which is likely to be flooded. MUDSLIDEAREA OR MUDSLIDE PRONEAREA -An FLOOD PLAIN MANAGEMENT-The operation of area characterized by unstable slopes and land an overall program of corrective and preventive surfaces, whose history, geology, soil and bed- measures for reducing flood damage, including rock structure as well as climate indicate a but not limited to emergency preparedness potential for mudslides. plans, flood control works and flood plain management regulations such as zoning ordi- NEW CONSTRUCTION-For purposes of deter- nances, building codes, health regulations, mining rates, means those structures the con- grading ordinances and erosion control ordi- struction or substantial improvement of which nances. is begun after December 31, 1974, or the effec- tive date of the publication of the Flood Insur- FLOOD RELA TED EROSION-The collapse or sub- ance Rate Map (FIRM), whichever is later. New sidence of land along the shore of a lake or construction, for the purposes of determining other body of water as a result of undermining rates, also means those mobile homes within caused by waves or currents of water exceeding mobile home parks for which construction has anticipated cyclical levels or suddenly caused started after December 31, 1974, or the effective by an unusually high water level in a natural date of the publication of the Flood Insurance body of water, accompanied by a severe storm Rate Map (FIRM), whichever is later and which or by an abnormal tidal surge or by some simi- are located within a new mobile home park, an larly unusual and unforeseeable event which expansion to an existing mobile home park, or results in flooding. within an existing mobile home park where the repair, reconstruction or improvement of HABITABLE FLOOR-Any floor used for living, streets, utilities, and pads equals or exceeds 50 which includes working, sleeping, eating, percent of the value of the streets, utilities and cooking or recreation, or combination thereof. pads before the repair, reconstruction or im- A floor used only for storage purposes is not a prbvement has commenced. New construction, Habitable Floor. for the purposes of flood plain management regulations, means construction started after INUNDATION-A condition of flooding ora flow of the effective date of a flood plain management mud characterized by: The overspreading with regulation adopted by a community. water or a wet softened mass of debris or plastic soils. REGULAR PROGRAM-The Regular Flood Insur- ance Program under which buildings con- MEAN SEA LEVEL-The average height of the sea structed on or before December 31, 1974, (or for all stages of the tide over a nineteen year before the effective date of the Flood Insurance period, usually determined from hourly height Rate Map, if later), as well as those structures 'observations on an open coast or in adjacent located butside of the special flood hazard waters having free access to the sea. areas built after that time, remain eligible for 5-1 1 the first layer of insurance coverage at either STORM CELLAR-A room below grade, the total actuarial rates or subsidized rates, whichever area of which is large enough only to accommo- are lower. All other buildings require actuarial date the occupants of the structure as a means rates on both layers of coverage. Regardless of of temporary shelter against severe tornado and date of construction, actuarial rates are always similar wind storm activity. required for the second layer of coverage, which is made available upon the effective date of the STRUCTURE OR BUILDING-A walled and roofed Flood Insurance Rate Map. In return for such building other than a gas or liquid storage tank, additional flood insurance coverage, a commu- that is principally above ground and affixed to a nity is required to adopt additional Flood Plain permanent site, as well as a mobile home on Management Regulations in accordance with foundation. The term includes a building under the specific flood hazard data provided on the construction or repair, but does not include Flood Insurance Rate Map. building materials or supplies unless they are within an enclosed building on the premises. SPECIAL FLOOD HAZARD AREA-The maximum area of the flood plain that, on the average, is SUBSIDIZED RA TES-The rates which involve sub- likely to be flooded once every 100 years i.e. sidizations by the Federal Government to en- will be flooded during a base flood. courage the purchase of the first layer limits of flood insurance on existing structures at START OF CONSTRUCTION-The first placement reasonably affordable costs. of permanent construction of a structure on a site, such as the pouring of slabs or footings or SUBSTANTIAL IMPROVEMENT-Any repair, recon- any work beyond the stage of excavation. For a struction, or improvement of a structure, the structure without a basement or poured foot- cost of which equals or exceeds 50 percent of ings, the start of construction includes the first the market value of the structure either (a) be- permanent framing or assembly of the structure fore the improvement is started or (b) if the or any part thereof on its pilings or foundation structure has been damaged, and is being re- for sites other than mobile home parks, or the stored, before the damage occurred. For the affixing of any prefabricated structures to its purposes of this definition, "substantial im- permanent site. Permanent construction does provement" is considered to occur when the not include land preparation such as clearing, first alteration of any wall, ceiling, floor or other grading, and filling; nor does it include the in- structural part of the building commences, stallation of streets and/or walkways; nor does whether or not that alteration affects the ex- it include excavation for basement, footings, ternal dimensions of the structure. The term piers, or foundations or the erection of tempo- does not, however, include either (1) any altera- ary forms; nor does it include the existence on tion to comply with existing state or local the property of accessory buildings, such as health, sanitary, building, or safety codes or garages or sheds not occupied as dwelling regulations or (2) any alteration of a structure units or not a part of the main structure. For listed on the National Register of Historic mobile home parks which are equipped with Places ora State Inventory of Historic Places. concrete pads on which mobile homes are to be placed, "start of construction" means the time WATER SURFACE ELEVATION-The heights in re- at which the pouring of the pads has begun. For lation to Mean Sea Level expected to be reached mobile home parks which are not equipped with by floods of various magnitudes and frequen- concrete pads, "start of construction" means cies at pertinent points in the flood plain. the date on which the installation of utilities and final site grading are completed, and all VARIANCE-A grant of relief by a community to a park roads are completed and paved. person from the terms of a flood plain manage- ment regulation permitting construction in a STATE COORDINA TING AGENCY-The agency of manner otherwise prohibited by the regulation the state government designated by the and where specific enforcement would result in Governor of the state at the request of the unnecessary hardship. Administrator to coordinate the flood insurance program in that state. 5-12 Flood Plain / Flood Fringe Floodway Flood Fringe /~o, BaseFlood Level FIGURE 5-1 River Valley Cross Section 5-13 ANNOTATED BIBLIOGRAPHY FLOOD LEGISLATION AND RELATED key areas: insurance, flood plain management, and local REPFL~ OODRT LEGI~SLATION~ community consultation and appeals procedure. REPORTS Department of Housing and Urban Develop- Department of Housing and Urban Develop- ment. Title 24, Chapter X, Subchapter 13, ment. Insurance and Other Programs for Amendments to Subchapter Necessitated Financial Assistance to Flood Victims. Financial Assistance to Flood Victims g by Legislation. Washington, D.C.: H.U.D., Washington, D.C.: Government Printing January 1, 1974. This is a list of amendments to the Title 24 regulations This report was required by the Southeast Hurricane governing the national flood insurance program. Disaster Relief Act of 1965 (Public Law 89 - 339). It pro- vided the background data and analysis for the National Flood Insurance Act of 1968. The report viewed flood insurance as a means of helping the individual bear more easily the risks of flood damage to which his location often exposes him, and, equally, as a means of discourag- ing unwise occupancy of flood-prone areas. � National Flood Insurance Act of 1968 As Amended. Washington, D.C.: Govern- BOOKS AND SEPARATELY PUBLISHED ment Printing Office, 1971. MATERIAL This Act authorized a flood insurance program by means of which flood insurance, over a period of time, was made available on a nationwide basis through the co- operative efforts of the Federal Government and the pri- vate insurance industry. The title also encouraged state American Concrete Institute. Building Code and local governments to minimize and restrict develop- Requirements for Reinforced Concrete ment in flood prone areas through appropriate land use adjustments. Damage and loss from mudslides was also recognized as part of the flood problem by this legisla- Concrete Institute, 1971. tion. American Creosote Works, Inc. Appendix I, Title 24 - Revised As Of April 1, 1973. American Society Testing Materials Specifi- Reprinted from Code of Federal Regula- cations for Round Timber Piles, D25 - 58. tion. pp. 30- 34. This publication contains the guidelines, rules and reg- These specifications cover round timber piles to be ulations a community must follow to become eligible and used untreated or treated with standard preservatives. remain eligible for the Flood Insurance Program. It has Most piles are manufactured and sold under these speci- been amended to conform to the Flood Disaster Protec- fications tion Act of 1973. American National Standards Institute, Inc. United States Senate, Committee on Banking, American National Standard Specifications American National Standard Specifications Housing and Urban Affairs. Report on and Dimensions for Wood Poles, ANSI Flood Disaster Protection Act of 1973. and Dimensions for Wood Poles, ANSI Report No. 93 - 583, 93rd Congress, 1st 05.1 - 1972. New York: American Session, 1973. National Standards Institute, August 1972. This standard consists of specifications and dimensions This report reviews a bill (H.R. 8449) to expand the for wood poles that are to be treated with preservatives. national flood insurance program by increasing limits of coverage and total amount of insurance authorized to be outstanding and by requiring known flood prone com- American Wood Preservers Institute. A WPI munities to participate in the program. It is a good pre- Technical Guidelines for Pressure- Treated sentation of data and the issues involved. Selection of Treated Timber Piling. Wood: Selection of Treated T/mber Piling. United States Congress. Flood Disaster Protec- McLean, Virginia: American Wood Pre- tion Act of 1973. 93rd Congress, 1st Ses- servers Institute, 1971. sion, January 3, 1973. This eight-page publication thoroughly reviews ASTM standard D25 - 70, Round Timber Piles. It points out The Act extends the emergency flood insurance pro- that use of D25 - 70 will greatly increase efficiency and gram through December 31, 1975, and addresses three economy in pile construction. 5-15 FHA Pole House Construction. Washing- flood insurance is contained in this manual. The rules and requirements for flood insurance are reviewed and ton, D.C.: American Wood Preservers In- rate tables and sample forms are presented. stitute, 1971. An excellent basic manual on the engineering and con- National Water Commission. New Directions in struction of pole houses. Useful tables and details are U.S. Water Policy, Summary, Conclusions presented. and Recommendations. Washington, D.C.: Anderson, L. 0. and Smith, Walton R. Houses Government Printing Office, 1973. Can Resist Hurricanes. Madison, Wiscon- A thorough analysis of U.S. water problems and sin: U.S. Forest Products Laboratory, recommendations for water resource management. sin: U.S. Forest Products Laboratory, 1965. Patterson, Donald. Pole Building Design. Wash- A 48-page paper presenting construction methods, ington, D.C.: American Wood Preservers materials, and details to resist hurricane damage. Existing, hurricane codes and factors to consider in new codes are Institute, 1972. reviewed. This is a good presentation with much of the This 48-page manual covers the engineering and pre- data applicable to flood resistant construction. servative treatment of wood poles and piles in a most complete manner. All the formulas, tables, and explana- tory notes necessary for good design are presented. Degenkolb, H. J. and Associates. Design Notes and Criteria Pole Type Buildings. San Shaeffer, John R. Introduction to Flood Proof- Mateo, California: J. H. Baxter Co., 1968. ing, An Outline of Principles and Methods. A brief review of a structural design method for pole: University of Chicago, 1967. type buildings. Sixty pages of flood proofing techniques for both resi- dential and commercial properties. General Adjustment Bureau, Inc. Floodwaters, Everybody's Problem. New York: General Sumrall, Clinton L., Jr. Prudent Construction in Adjustment Bureau, 1973. the Flood Plain. Varna, Bulgaria: 8th An insurance industry publication providing a very good overview of the scope of the nation's flood problem. Irrigation and Drainage, May 1972. Nature's Destructive Forces. New York: This paper says that many areas within flood plains can be economically utilized for development if adequate General Adjustment Bureau, 1973. consideration is given to flood problems and proper en- A review of the characteristics and forces associated gineering techniques are applied. Examples of various with the various types of wind storms that occur in the "prudent" types of construction are reviewed. U.S. and the forecasting and protection methods that are available. Southern Forest Products Association, National Forest Products Association, and American The Hartford. Flood-Proofing, A Technique of Wood Preservers Institute. How to Build Wood Preservers Institute. How to Build Avoiding Flood Damage. n.p., n.d. Ob- tained from The Hartford Insurance Group, Storm Resistant Structures. n.p., n.d. Hartford, Conn. A short manual of construction details. Designed to increase safety and building resistance to storms and This 12-page manual is a presentation of some basic floods. techniques for protecting property from flood damage if it is located in a flood hazard area. Tennessee Valley Authority. Flood Damage Kusler, Jon A. and Lee, Thomas M. Regulations Prevention: An Indexed Bibliography. for Flood Plains, Richard Spicer, ed. Knoxville, Tennessee: Tennessee Valley Chicago: American Society of Planning Authority, August 1973 (7th ed.) Officials, 1972. A comprehensive bibliography of flood related publi- cations listed by publication date. It covers the period A comprehensive discussion of the necessity for, the from 1920 to 1973. 496 entries. problems of, and approaches to flood plain management. United States, Department of Commerce, Nation National Flood Insurers Association. National Oceanicand Atmospheric Admin- Flood Insurance Program - Flood Insurance istration. Floods, Flash Floods and Warn- Manual, N FIA - ED 7/74. New York: ings. Washington, D.C.: Government National Flood Insurers Association, July Printing Office, 1973. 1974 This is a six-page flyer on the scope of flash flooding Ail the basic information for obtaining and writing in the U.S. and a review of how people and communities can protect themselves from them. 5-16 Department of Housing and Urban Devel- VI. Washington, D.C.: Government Print- opment. Criteria for Compacted Fills. ing Office, 1971. Washington, D.C.: Government Printing This second volume is a more detailed investigation of Office, 1973. (4075.6). techniques for regulating subdivisions of land in riverine and coastal flood hazard areas. It contains draft regula- A Comprehensive review of criteria for fills for tions for flood hazard areas. single and multi-story residential properties. , Minimum Property Standards for . The Nation's Water Resources. One and Two Family Dwellings. Washing- Washington, D.C.: Government Printing ton, D.C.: Goverment Printing Office, Office, 1968. 1973. A comprehensive assessment of the water and land related resources of the U.S. It has sections reviewing Revised Minimum Property Standards. They are ori- flooding and flood control. This is a good reference re- ented toward stating requirements in performance terms. source. �__ ._ _ Slope Protection for Resi- United States Army, Corps of Engineers, Albu- dential Developments. Washington, D.C.: querque District. Flood Plain Management Government Printing Office, 1973. (4075.7). Services. Albuquerque, New Mexico: De- Recommendations for improving slope stability and partment of the Army, June 1967. controlling slope erosion. This is a one-page flyer outlining the flood related ser- vices of the Army Corps of Engineers. _ i When You Return to a Storm Damaged Home. Washington, D.C.: Gov- , , Galveston District. Appendix B. ernment Printing Office, 1972. Criteria Relating to the Adoption of the This booklet thoroughly reviews the economic and 3-Foot Breaking Wave. Galveston, Texas: safety steps the home owner should take to put his flood Department of the Army, n.d. damaged home and its contents back in operating and A discussion of wave forces on standard wood frame living condition. construction. /Federal Housing Administration. , , Vicksburg District. Guidelines for Minimum Property Standards For One and Reducing Flood Damages. Vicksburg, Miss Two Living Units. Washington, D.C.: Mississippi: Department of the Army, Government Printing Office, 1966. May 1967. A ten-page manual reviewing three ways to prevent Minimum Standards for constructing safe, well plan- flood damages: control over the river, control over the ned and soundly built homes that will be eligible for land and other measures mortgage insurance. mortgage insurance. land, and other measures. Federal Insurance Administration. , Office of the Chief of Engineers. Flood- Flood Insurance Study Guidelines, Proofing Regulations. Washington, D.C.: HUD-1-58. Washington, D. C.: Govern- Government Printing Office, 1973. ment Printing Office, April 1974. This 77-page manual is one of the most comprehensive flood-proofing publications yet available. It is written in a Presents a step-by-step procedure for defining the code format that is adaptable for use in local building flood hazard conditions of an area. These guidelines codes. must be followed by Agencies and/or Consultants performing Flood Insurance Studies for the Federal Insurance Administration. , Water Resources Council. Regulation of Flood Hazard Areas to Reduce Flood Losses. Vol. I, Parts I-IV. Washington, ARTICLES & PERIODICALS D.C.: Government Printing Office, 1970. This volume explores selected issues in regulation of private and public land uses as a tool of flood plain man- agement. It focuses primarily on basic regulatory issues Dorram, Peter B., "Flood Loss Reduction through and riverine flood problems. through Planning and Regulating Flood Plain Development," Federal Planning In- _, __. Regulation of Flood Hazard Areas formation Report (N.J.) 5, No. 3 (May to Reduce Flood Losses. Vol. II, Parts V-V 1970). 5-17 Mr. Dorram's paper reviews planning approaches and ment of Criteria for Evaluating Alternative zoning and code regulations that can be applied to mini- Flood Damage Prevention Measures with mize flood losses. 75d from Executive Secretary, N.J. Federation of Planning Officials, 1308 Wood Valley Road, Lmited Information: CaseStudyof Road, Mountainside, N.J. 07092. Martins Ferry, Ohio." Prepared for State of Ohio, Department of Natural Resources, Haddon, William, Jr., "On the Escape of Tigers: Flood Plain Management Section, Decem- An Ecologic Note," from Technology Re- ber 12, 1973. view 72, No. 7 (May 1970). This 62-page report develops criteria for assessing This short paper proposes a systematic technique flood damage prevention alternatives. The report for identifying loss reduction strategies resulting from attempts to specify the types of data needed, assess the the transfer of energy. availability of the data, and suggest methods for dealing with inadequate information. Lin, T. Y. and Talbot, W. J., Jr., "Pretensioned Plaquemines Parish Commissioners. "Storm Re- Concrete Piles, Present Knowledge Sum- sistive Construction for Plaquemines Parish, marized," Civil Engineering (May 1961). La." [1970?] A six-page review of the design, detailing, manufac- Th ture, driving, and applications of pretensioned concrete tion subjected to Hurricane Camille's (1969) destruct forces. It presents 28 pages of building details and methods for minimizing storm damage to residences. Phippen, George R., "A New Course to Ararat," Water Spectrum 3, No. 2 (Summer 1971): Sutton, Walter G. "Planning for Optimum 9 - 15. Economic Use of Flood Plains," ms. Feb- This is an excellent background article on flood plain ruary 1963. Done at Atlanta, Georgia. management. It reviews the attitudes, consequences, ap- A short paper comparing the alternative costs of site proaches, economics, federal involvement and future of development in and out of the flood plain. flood plain management. Wall, Glenn R. Administrative Law and the Use of Flood Plain Lands. Lexington, Univer- UNPUBLISHED RMATERIAL sity of Kentucky, Spring 1968 (Repro- duced and distributed by Tennessee Valley Authority). Lee, Thomas M., ."Factos in Floodway Selec- and A good analysis of the legal background, concepts, and precedents of administering flood plain regulations. tion." Paper presented at the August 18 - 20, 1971 ASCE, 19th Specialty Conference Establishing an Engineering Basis for of the Hydraulics Division, Iowa City. Flood Plain Regulations. MA Thesis. Uni- A 32-page paper intended to acquaint the engineer versity of Tennessee, December 3, 1969. with the planning, social, and political aspects involved in floodway selection. The floodway being the river channel (Reproduced and distributed by Tennessee and adjacent flood plain needed to effectively convey Valley Authority). flood flows. This Master's thesis' thoroughly tests the hypothesis that "the use of land use controls is a desirable and legal Moore, John L., Middlebrooks, Burton, and element in any plan for reducing flood damage when sup- Crawford, Beth. Battelle Columbus Labor- ported by an adequate engineering basis." After testing Crawford, Beth. Battelleolubus Labor- the hypothesis a process is proposed by which community atories. "Draft Final Report on Develop- officials can reach decisions concerning the flood problem. lem. 5-18 ACI(NOWLEDGEMENTS This report was prepared by the Federal Insurance Administration of the Department of Housing and Urban Development. The following provided cost estimating data for the foundation types reviewed in this manual: Roy D. Rainey & Co., Little Rock Arkansas; James R. Pittner, Davenport, Iowa; Ryan Homes, Pittsburgh, Pennsylvania; Byers Construction Co., Altus, Oklahoma; Whitewood Post & Pole Co., Whitewood, South Dakota; Roanoke Wood Preservers, Roan- oke, Virginia; W. Paynter Sharpe and Sons, Inc., Milton, Delaware; Agway, Inc., Syracuse, New York; Miller Leisure Homes, Inc., Dauphin Island, Alabama; John C. Cahill, Associ- ates, Rehoboth Beach, Delaware; J. H. Baxter & Co., San Mateo, California; Umbaugh Pole Building Co., Inc., Ravena, Ohio; and the FHA offices in Cincinnati, Ohio; Denver, Colorado; Memphis, Tennessee; Sacramento, California; Albany, New York. The following architectural firms provided design concepts: Zane Yost and Associates, Bridgeport, Conn.; KEF Corporation, Metairie, La.; Keck and Keck Architects, Chicago, III.; and Duval/Johlic Architects-Planners, San Francisco, Ca. Background data and design concepts were contributed by Louisiana State University, Department of Architecture; Rhode Island School of Design; University of California at Los Angeles, School of Architecture and Urban Planning; and University of Miami School of Architecture. PHOTO CREDITS PAGE vii 1st column - General Adjustment Bureau, Inc., New York, N.Y. viii 1st column - American Red Cross, Washington, D.C. ix 2nd column - American Red Cross, Washington, D.C. x 2nd column - General Adjustment Bureau, Inc., New York, N.Y. 1-5 2nd column - American Red Cross, Washington, D.C. 1-14 Middle - Howard Anderson, Architect, Del Mar, California 5-19 * U. S. GOVERNMENT PRINTING OFFICE: 1976 O - 222-193