[Federal Register Volume 59, Number 77 (Thursday, April 21, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-9689]


[[Page Unknown]]

[Federal Register: April 21, 1994]


_______________________________________________________________________

Part IV

 

Department of Housing and Urban Development





Office of the Assistant Secretary for Housing-Federal Housing 
Commissioner





24 CFR Part 3280
Interpretative Bulletin for Manufactured Home Construction and 
Safety Standards; Final Rule
DEPARTMENT OF HOUSING AND URBAN DEVELOPMENT

Office of the Assistant Secretary for Housing-Federal Housing 
Commissioner
[Docket Nos. R-94-1497; FR-2622-N-06; and R-94-1632; FR-3380-N-05]

24 CFR Part 3280

Interpretative Bulletin for Manufactured Home Construction and 
Safety Standards

AGENCY: Office of the Assistant Secretary for Housing-Federal Housing 
Commissioner, HUD.

ACTION: Notice of interpretative bulletin.

-----------------------------------------------------------------------

SUMMARY: HUD published two final rules amending the Federal 
Manufactured Home Construction and Safety Standards (FMHCSS) on October 
25, 1993 (58 FR 54975), and January 14, 1994 (59 FR 2456). Technical 
corrections for the two rules were published on March 31, 1994 (59 FR 
15113). This notice publishes an Interpretative Bulletin that the 
Department has issued to clarify some aspects of the new standards that 
have been the subject of questions from the industry and the public.

DATES: Issued April 15, 1994.

FOR FURTHER INFORMATION CONTACT: David C. Nimmer, Director, Office of 
Manufactured Housing and Regulatory Functions, Department of Housing 
and Urban Development, 451 Seventh Street SW., ATTN: Mailroom B-133, 
Washington, DC 20410-8000. Telephones: (voice) (202) 755-7410; (TDD) 
(202) 708-4594. (These are not toll-free numbers.)

SUPPLEMENTARY INFORMATION: Accordingly, the following Interpretative 
Bulletin, which includes the Secretary's finding that it should not be 
subject to notice-and-comment rulemaking, has been issued by the 
Department:

Interpretative Bulletin to the Standards

Manufactured Home Construction and Safety Standards 24 CFR Part 3280

    Under Section 604 of the National Manufactured Housing Construction 
and Safety Standards Act of 1974, 42 U.S.C. 5403, the Secretary of the 
U.S. Department of Housing and Urban Development (``HUD'') is 
authorized to issue, amend and revoke by order appropriate Federal 
manufactured home construction and safety standards. On October 25, 
1993, (58 FR 54975) and January 14, 1994, (59 FR 2456), HUD published 
certain changes to the Federal Manufactured Home Construction and 
Safety Standards for energy conservation standards and new standards 
for high wind areas, respectively. The effective date of the energy 
standards is October 25, 1994, while the wind standards are effective 
on July 13, 1994.
    Since the publication of these two rules, the Department has 
received a number of questions asking for clarification of certain 
provisions of the rules. Those who requested the clarifications urged 
the Department to provide a timely response so that industry designers 
can move forward to revise plans and specifications well ahead of the 
effective dates of the new standards. HUD recognizes that it is 
imperative to respond to these requests for clarification as soon as 
possible to assist Primary Inspection Agencies (``PIAs''), 
manufacturers and State Administrative Agencies in understanding the 
changes to the manufactured housing standards well in advance of their 
effective dates.
    Based on these requests for clarifications, discussions with 
manufacturers and PIAs and the fact that many of the changes to the 
standards concern issues of public safety, the Department has concluded 
under 24 CFR 3282.113 of the Manufactured Home Procedural and 
Enforcement Regulations that the immediate issuance of guidance to 
address these technical questions is in the public interest and 
necessary for the orderly redesign of manufactured homes to meet these 
two standards before their effective date. Therefore, due to the need 
for expeditious resolution of these issues and due to that fact that 
this is not a change in the position or policy of the Department but 
merely involves technical clarifications, the Secretary deems it not to 
be in the public interest to issue these interpretations for public 
comment in the Federal Register or to otherwise treat this 
Interpretative Bulletin as rulemaking. The Department is providing this 
guidance to manufacturers and PIAs so that they can proceed immediately 
with the redesign of their homes. Where necessary, the Department may 
provide further assistance in these new standards by letter of 
clarification or by a new Interpretative Bulletin.
    The requested clarifications of the Manufactured Home Construction 
and Safety Standards have been organized into the following questions 
and answers. While the majority of the questions relate to the 
interpretation of the standards, several of the questions relate to the 
enforcement of the standards.
    In addition to those answered below, there are several questions 
which have been submitted to HUD that require additional technical 
analysis before a decision can be made. These questions will be 
addressed in a future Interpretative Bulletin or rulemaking.
    Other questions revealed the need for corrections to mistakes 
within the language of the rules and a few questions raised issues that 
require additional rulemaking. The editorial corrections were made in a 
correction document published in the Federal Register on March 31, 1994 
(59 FR 15113).

I. The Energy Standards

    Questions: 1. The Effective date of the rule is October 25, 1994. 
Does this mean that every home that enters production that day is to be 
built under the new regulations?
    Answer: Yes.
    2. 24 CFR 3280.103(b)(2)--Would the required kitchen/bath fans 
constitute a means of achieving the required 0.10 ACH if automatic 
timers are used to control the fans? This is what the Bonneville Power 
Administration, accepts for whole house ventilation for their Super 
Good Cents Program.
    Answer: No. These fans are for spot ventilation and may not 
effectively change the air in other parts of the home.
    3. 24 CFR 3280.103(b)(2)--Does 0.035 cfm/sq. ft. floor area have to 
be used to calculate the required system capacity, or can 0.10 actual 
house volume/60 min. be used as an alternative?
    Answer: Utilize 0.035 cfm/sq. foot floor area. This formula 
compensates for the decrease in natural ventilation when ventilation 
fans are in operation.
    4. 24 CFR 3280.103(b)(3)--This section requires whole house 
ventilation, but limits the positive or negative pressures, depending 
on the thermal zone. What is meant by ``Mechanical systems shall be 
balanced?''
    Answer: The capacity of the intake fans shall be the same as the 
exhaust fans.
    5. 24 CFR 3280.103(b)(3)--Would the equipment for Zones 1 and 2 
have to be different? Does this mean a house constructed to Zone 2 
insulation cannot be shipped to thermal Zone 1 because of the 
ventilation system?
    Answer: It doesn't have to be different. A Zone 2 home with a 
balanced mechanical system would be acceptable in Zone 1. Manual or 
fixed louvers would be acceptable in both zones. One way registers 
(i.e. those which react to pressure) have to be appropriate to the 
zone. In Zones 2 and 3, a one way register should be set to relieve a 
positive interior pressure. In Zone 1, a one-way register should be set 
to relieve a negative interior pressure.
    6. 24 CFR 3280.103(b)(3)--It is also stated that such systems must 
be ``balanced'' so as to release any ``unbalanced pressure.'' Isn't it 
true that a balanced system would not have any positive or negative 
pressures? Is this two ways of saying the same thing, or are both 
stipulations necessary?
    Answer: Both stipulations are necessary. Please refer to the 
answers in Questions 4 and 5 for a base reference. A system, for 
example, is considered balanced when the fan capacities are equal. A 
passive system is balanced when the system can be expected to release 
any unbalanced pressure. In actual situations, however, it is 
recognized that the deliberate movement of air causes unbalanced 
pressures and this is the reason for the prescription on positive and 
negative pressures.
    7. 24 CFR 3280.103(b)(3)--What kind of mechanical ventilation 
systems do not create pressure differences? Is the presence of a nearby 
equivalent passive system enough to say that the system is 
``balanced''?
    Answer: It is recognized that in operation, mechanical systems 
create unbalanced pressures. Please refer to the answer for Question 6. 
Where the passive portion of a system is evaluated as the functional 
equivalent of the mechanical portion, the system is balanced. An 
equivalent passive system is enough to say the system is balanced. 
However, if the intake and the exhaust are nearby and there is no 
provision to circulate the incoming air throughout the house, then 
there is no whole house ventilation.
    8. 24 CFR 3280.103(b)(5)--Would a mechanical system, that works in 
conjunction with the furnace, and introduces outside air into the home, 
but does not exhaust inside air, meet the ventilation requirements if 
bath/kitchen fans can be used to exhaust inside air?
    Answer: No. A mechanical system that works in conjunction with the 
furnace is acceptable; however, bath and kitchen fans are not 
acceptable for the exhaust.
    9. 24 CFR 3280.103(b)(5)--If the answer to the above question is 
``No'', then would adding a separate exhaust fan, in addition to the 
above system, meet the requirement?
    Answer: Yes.
    10. 24 CFR 3280.103(b)(5)--Would adding a one-way register (to 
depressurize the house) meet the requirements?
    Answer: Yes; (The one way register should depressurize only in 
Zones 2 and 3).
    11. 24 CFR 3280.103(b)(6)--This section requires a manual control 
on the ventilation system. 24 CFR 3280.103(b)(5) says the ventilation 
system may be integral with the heating and cooling equipment. Does 
this mean that the homeowner must be able to operate the ventilation 
system independently of the furnace, or can the two share the same 
controls?
    Answer: They can share the same controls and the ventilation system 
can be designed to operate in conjunction with and simultaneously with 
the furnace or air conditioner. An automatic control to operate the 
system independently of the furnace or air conditioner is permitted. 
However, in all circumstances there must be the capability for the 
homeowner to operate the system continuously and independently of any 
other automatic provision.
    12. 24 CFR 3280.103(b)(7)--This section says that the ventilation 
capacity must be substantiated. What types of calculations or tests are 
acceptable?
    Answer: With mechanical ventilation, a fan or fans rated to provide 
the required cfm is sufficient. Concerning passive systems, rational 
assumptions and engineering calculations, or tests will be acceptable 
when based upon recognized principles and practices. For example, 
ASHRAE Chapter 23 can be used as a resource.
    13. 24 CFR 3280.303(g)--Do old, existing tests that are retested 
for slight material changes have to be submitted to the Department for 
another review?
    Answer: The existing tests do not need to be resubmitted unless:
    1. Minor material substitutions were not verified by tests or 
engineering analysis by a professional engineer or architect as having 
equivalent or superior strength to the material being replaced; or
    2. No follow-up testing has been conducted; or
    3. Tests were not witnessed by a licensed professional engineer or 
architect; or
    4. Higher design loads are required to be used by the new wind 
standards which are effective on July 13, 1994.
    14. 24 CFR 3280.303(g)--How will the Department notify other 
manufacturers of a recently approved protocol? Will a new test protocol 
be distributed to everyone or will it be considered the property of the 
developing manufacturer?
    Answer: The Department will not usually notify other manufacturers 
since new protocols are often of a proprietary nature.
    15. 24 CFR 3280.303(g)--How will the Department assure the 
manufacturer of a prompt response to a protocol review? Will the 
Technical Exchange Group be able to develop protocols and ask the DTAG 
to approve and distribute them?
    Answer: The Department will make every effort to review test 
protocols promptly in those cases where manufacturers will not be using 
recognized testing procedures. We do not anticipate that the Technical 
Exchange Group will be asked to develop test protocols.
    16. 24 CFR 3280.504(c)(1)(i)--Does Section 24 CFR 3280.504(c)(1)(i) 
allow construction of ventilated roof homes without eaves (e.g. single 
section homes) but with ``low roof vents?'' If so, is a 1 inch space 
required between the top of the insulation and the roof sheathing when 
there is no designed air passage to that point?
    Answer: Where eaves or overhangs are not part of the design, low 
roof vents can be used. However, a 1-inch minimum air space directly 
underneath the most outboard point of the vent is needed for a fresh 
air path for the length of the home to insure that the low roof vents 
function.
    17. 24 CFR 3280.504(c)(2)--Would polystyrene or R-5 fiberglass 
insulation be considered sheathing, if it is installed over the roof 
truss top chord on metal roof units, and if it is to be used as a sound 
deadener? The requirement states ``. . . homes constructed with metal 
roofs and having no sheathing or underlayment installed, are not 
required to be provided with attic or roof cavity ventilation . . . ''. 
Is the above type of roof construction required to be ventilated?
    Answer: A rigid polystyrene sheath would be considered a sheathing. 
Fiberglass batts would not be. The rigid polystyrene sheath would 
require the roof to be ventilated.
    18. 24 CFR 3280.506(a)--``The overall coefficient of heat 
transmission (Uo) of the manufactured home for the respective zones and 
an indoor design of 70  deg.F, including internal and external ducts, 
and excluding infiltration ventilation and condensation control, shall 
not . . . '' Should there be a comma (,) between infiltration and 
ventilation? If the answer is yes, does this mean to exclude only the 
passive and/or active 0.10 air changes per hour referred to in 24 CFR 
3280.103(b)(2), and/or does this mean the 0.10 ACH ``plus'' the natural 
infiltration and exfiltration of 0.25 ACH referred to in 24 CFR 
3280.103(b)? If the answer is no, what does this mean?
    Answer: A comma (,) should be between infiltration and ventilation, 
and the 0.10 ACH and the 0.25 ACH are excluded from the calculation.
    19. 24 CFR 3280.508--How is duct loss calculated when duct is 
located (sic) between the floor insulation and the floor (conditioned 
area) for single wides? We suggest there is none.
    Answer: Refer to paragraph 3.2 of the document ``Overall U-values 
and heating, cooling loads Manufactured Homes''. The duct losses for 
this configuration are not included in the calculation. The space where 
the duct is located is considered conditioned and the floor deck is not 
included in the calculation.
    20. 24 CFR 3280.508--What is the duct loss factor when the duct is 
located between the floor insulation and the floor for double wides 
except for the crossover duct? We suggest 2% of calculated transmission 
(Uo) loss.
    Answer: The external ducts are considered to be a component of the 
homes. The area of the duct exposed to the exterior and the level of 
insulation installed are summarized with the overall envelope area. 
Please note that 24 CFR 3280.506 (a) prevails over paragraph 4.4 of the 
document ``Overall U-values and heating, cooling loads Manufactured 
Homes''.
    21. 24 CFR 3280.508--Are people loads (one person per bedroom plus 
one) and appliance loads (1,200 BTUH) ignored when calculating 
``maximum'' heat loss allowed by the Uo? We assume this is ignored, 
except when estimating annual energy usage if desirable under 24 CFR 
3280.508(f), ``Annual Energy Used Based Compliance.
    Answer: People loads are not included in the determination of the 
Uo, when the ``Annual Energy Used Based Compliance'' method is used (24 
CFR 3280.508(b)1). This section says that all heat loss calculations 
should be consistent with the procedures in the February 1992 document 
by PNL.
    22. 24 CFR 3280.506(a)--24 CFR 3280.506(a) says that internal and 
external duct losses must be considered. The PNL document does not 
include duct losses. Will the PNL document be revised to include such 
losses in the overall Uo heat loss?
    Answer: There are no current plans to revise the PNL document. It 
is subject to change by addition or clarification if there is a need to 
do so.
    23. 24 CFR 3280.508--If external duct losses are to be considered, 
can the additional area of the cross-over duct be used in the summation 
of the overall envelope area? If not, it would have to be considered a 
pure loss.
    Answer: The external ducts are considered to be a component of the 
homes. The area of the duct exposed to the exterior and the level of 
insulation installed are summarized with the overall envelope area.
    24. 24 CFR 3280.508(b)--Blown Insulation:--In appendix B (Page b(i) 
of the PNL document), the R-value of blown insulation is taken at R-2.5 
per inch. In the earlier example (Page 4.4), it is shown to be 3.67 per 
inch. Which is correct?
    Answer: The allowed R-value should be determined from the 
recognized R-value for the product employed.
    25. 24 CFR 3280.508(b)--Insulation in Ceiling: Regarding the 
examples on Page 54976, is the R-value in the ceiling the total, 
``nominal'' thickness at the peak? Or is the lesser, ``effective'', or 
``installed'' value of the insulation in the cavity?
    Answer: The ``as installed'' value is to be used.
    26. 24 CFR 3280.508(d)--Section 3280.508(d) provides some potential 
for offering more value to the consumer by considering high energy 
efficiency heating and cooling equipment. Home manufacturers ordinarily 
install heating equipment but most cooling equipment is provided and 
installed by others. Will HUD allow manufacturers to specify on the 
data plate or elsewhere that the home is designed for minimum SEER 
(e.g. 12) air conditioning equipment and calculate the credit based on 
the design even though we do not actually provide the equipment?
    Answer: When the home manufacturer does not provide the cooling 
equipment, the higher energy efficiency credit cannot be used.
    27. 24 CFR 3280.510(b)--The requirement states ``. . . . heating 
equipment will maintain a 70 degree F temperature inside the home 
without storm sash or insulating glass in Zones 1 and 2, and with storm 
sash or insulating glass in Zone 3 . . . .''. Storm windows may be 
necessary to meet the significantly lower whole house ``U'' values 
required in 24 CFR 3280.506(a) for Zones 1 and 2, as well as Zone 3. 
For these homes, a certification temperature without storms makes no 
sense. For heat Zones 1 and 2, may the certification temperature be 
calculated with storm windows if said home is equipped as such?
    Answer: Yes; however, if removable storm windows are provided, the 
heat loss certification temperature will be calculated with the storms 
removed. For permanently installed double or triple glazing, the 
temperature may be calculated utilizing the window assembly U-value.
    28. 24 CFR 3280.806(b)(1). Receptacle outlets within 6 feet of the 
kitchen sink are now required to be GFCI. Neither section 210-7 of the 
NEC nor the NEC 1993 Handbook described the location of the receptacle 
clearly. How is this 6 feet measured? Is it along the wall behind the 
counter where the sink is located, or a 6-foot diameter circle at the 
sink corners, etc. * * *?
    Answer: It is measured between the receptacle and the nearest point 
on the sink. It is a point to point measurement. Refer to Figure 210-14 
in the 1993 NEC Handbook. 2.
    29. 24 CFR 3280.806(b)(1)--NEC 1993, 550-8(d) requires, ``Counter 
tops shall have receptacles located every 6 feet.'' Is a receptacle 
required to be 3 feet or 6 feet from the end of the counter top? Does 
this mean receptacles are to be 6 feet to 12 feet on center?
    Answer: According to 550-8(d), the six foot limit is measured 
between receptacles for the countertops. If the end of the counter is 
less than six feet from the receptacle, no additional receptacle is 
required.
    30. 24 CFR 3280.808(r)(1). Is a wall with wooden studs and gypsum 
paneling considered combustible?
    Answer: The purpose of paragraph (r) is to codify existing practice 
and interpretations concerning the maximum allowable gap. The \1/8\ 
inch gap applies to gypsum paneling as well as plywood paneling.
    31. 24 CFR 3280.808(r)(1)--Is the \1/8\'' gap addressing the size 
of the hole in the wall paneling? Or is it concerning the clearance of 
the rear of the box and other combustible materials, such as Lauan 
paneling? Or is it for both?
    Answer: It addresses the size gap permitted in the wall paneling.
    32. 24 CFR 3280.103(b)(2)--For whole House Ventilation: How should 
manufacturers figure the areas of calculation of additional ventilation 
of 0.10 air changes per hour. The Air Conditioning Contractors of 
America's Manual J used the conditioned space to determine the required 
CFM.
    A. Do you include the bath and the kitchen volume in the whole 
house volume?
    Answer: Yes.
    B. Do you include the partition's volume that surround the 
bathroom?
    Answer: Yes.
    C. Do you include the marriage wall and the endwall volume?
    Answer: Yes at the marriage wall; no at the endwall.
    D. Which dimension, interior or exterior side of walls, do you use 
to figure the volume of the house?
    Answer: The interior side of wall dimension may be used.
    33. 24 CFR 3280.805 (a)(3)(iii)--When is an appliance considered to 
be an ``other continuous duty load'' as prescribed in amended 24 CFR 
3280.805 (a)(3)(iii) for the purpose of adequately rating the appliance 
circuit?
    Answer: In Article 100 of the NFPA-70-1993 (the National Electrical 
Code) continuous duty is defined as: ``Operation at a substantially 
constant load for an indefinitely long time.'' To establish what is a 
constant load for an indefinitely long time, we must refer to the 
Article in the National Electrical Code for the specific appliance. If 
the specific requirements call for a branch circuit rating not less 
than 125% of the nameplate rating, then it is a continuous duty 
appliance. Some specific examples are: Article 422-14 (b) for water 
heaters, Article 424-3(b) for heating equipment, and Articles 440-32 
and 440-33 for air conditioning.

II. The Wind Standards

    Questions: 1. 24 CFR 3280--The effective date is July 13, 1994. 
Does this mean that every home that enters into the first stage of 
production on that date is to be under the new regulations?
    Answer: Every home entering the first stage of production as of 
July 13, 1994 must comply with the new wind safety provisions.
    2. 24 CFR 3280--In the preamble, page 2457, a statement is made 
that the Department expects to publish revised wind standards for the 
rest of the country ``next year.'' That statement may have been written 
in 1993. Please indicate when the Department expects to publish final 
regulations for the rest of the country.
    Answer: We plan to publish revised wind safety standards for the 
rest of the country sometime in 1994.
    3. 24 CFR 3280.304--On page 2463, the preamble indicates that the 
final rule permits the use of the 1991 NDS without exception. Please 
clarify that this reference standard shall be used in redesigning homes 
for Zones II and III not later than July 13, 1994, and for Zone I (the 
rest of the country) the standard shall be enforced not later than 
October 25, 1994.
    Answer: The use of the 1991 NDS will be enforced for designs in all 
Wind Zones, including existing Wind Zone I no later than July 13, 1994.
    4. 24 CFR 3280.5(f)--A new data plate entry is specified to 
indicate that a home has not been designed for ocean/coastal areas, 
within 1,500 feet of the coastline in Wind Zones II or III, unless it 
is designed under Exposure D, ASCE 7-88. It would seem that the 
homeowner will read this and be unsure whether or not the home is 
designed under either Exposure C or D. Recommend that the data plate so 
indicate in a positive statement where the home has been designed to be 
placed, under what exposure.
    Answer: The language on the data plate is clear and will avoid 
placement of homes which have not been designed for the higher design 
requirements of Exposure D from being installed too close to the 
coastline.
    5. 24 CFR 3280.5(g)--The new data plate statement concerning 
shutters is in conflict with the requirements of sections 24 CFR 
3280.403(f), .404(f), and .405(f). That is, the last sentence of the 
data plate statement strongly recommends that the home be made ready to 
be equipped with these devices. However, the sections listed above 
under Subpart E -Testing (page 2474), say that:
    (a) For homes in Wind Zones II and III manufacturers shall design 
exterior walls (make the homes ready) to allow for installation of 
protective covers over window and door openings, and
    (b) If the manufacturer does not provide protective covers, it must 
provide homeowner instructions for one method of protecting the 
openings, and
    (c) The instructions shall indicate whether devices, sleeves, or 
anchors for fasteners have been installed or provided by the 
manufacturer.
    Please modify the new data plate statement to track with these new 
requirements.
    Answer: The new data plate requirements are not in conflict with 
the provisions of 24 CFR 3280.403(f), .404(f) and .405(f).
    6. 24 CFR 3280.303(g)--Staples are not addressed in the 1991 NDS, 
but they are addressed in UM-25D. Can the 1.6 duration factor for wind 
from the 1991 NDS be applied to staples?
    Answer: The 1.6 load duration factor may not be applied to staples; 
however, a load duration factor of 1.33 may be used in accordance with 
UM-25-D.
    7. 24 CFR 3280.305(c)(l)(ii)--The new requirement for manufactured 
home wind loads for high wind areas requires that they shall be 
designed by a professional engineer or architect. This statement 
conflicts with an answer in the preamble (page 2465) which indicates 
that the Department will consider a suggestion for future rulemaking 
that a professional engineer prepare and certify wind load designs and 
calculations. Please clarify the new requirement.
    Answer: The wind resisting aspects of homes to be located in high 
wind areas must be designed by a Professional Engineer or Architect as 
specified by this section of the new wind safety requirements. The 
statement on Page 2465 of the Preamble should have indicated the 
Department's decision to require a professional engineer or architect 
to design homes in high wind areas.
    8. 24 CFR 3280.305(c)(1)(ii)--Please specify which designs and 
calculations shall be sealed by a registered professional engineer or 
architect. In that there is a DAPIA review of all drawings and 
calculations, it appears that sealing by a P.E. or architect should be 
greatly limited.
    Answer: As a practical matter, almost all aspects of the 
manufacturers designs are wind resisting elements and are required to 
be designed by a Registered Professional Engineer or Architect. This 
would include, but not be limited to, the following:
    a. all structural systems, assemblies, subassemblies or components 
and their connections or attachments
    b. exterior covering and sheathings
    c. Window and sliding glass door openings and designs for missile 
protection
    9. 24 CFR 3280.305 (c)(1)(ii)--This section permits the 
manufactured home to be designed either to option (A): Exposure C, ASCE 
7-88, or option (B): The wind pressures in the ``Table'' in the final 
rule. We have been advised by the engineering community for the 
conventional truss industry that truss designs in accordance with ASCE 
7-88 are prepared using criteria under ``main wind-force resisting 
systems,'' rather than under ``components and cladding.'' Please 
confirm that this standard engineering practice is acceptable for 
manufactured home trusses where either design options (A) or (B) is 
selected.
    Answer: Trusses are to be designed as ``Components'' and not as 
``Main Wind-Force Resisting Elements''. The only exception to this 
would be for a spatial truss framework which is designed as part of 
Main Frame System. Accordingly, roof trusses are to be designed as 
``Components'' under Subparagraph (A) or by using the design pressures 
specified in the ``Table'' in (B).
    10. 24 CFR 3280.305 (c)(1)(ii)--The ``Table'' entry for wall studs 
incorrectly shows the pressures for ``Within 3'0'' from each corner'' 
on the line above.
    Answer: The ``Table'' entry for wall studs does contain a 
typographical error in lining up the Design Pressure with the Element 
for wall studs ``Within 3'0'' from each corner of the sidewall and 
endwall''.
    11. 24 CFR 3280.305 (c)(1)(ii)--Studs are designed for a lateral 
load (38 PSF etc.) and no uplift load is specified. Does 
that mean no combined bending and axial tension is necessary for 
designing studs?
    Answer: Wall studs in sidewalls and endwalls are to be designed for 
combined uplift and lateral loads specified in ASCE 7 or by the Table 
of Design Wind Pressures.
    12. 24 CFR 3280.305 (c)(1)(ii)--For designing roof to wall, wall to 
floor and floor to chassis connections, what uplift load should be used 
``anchorage for lateral and vertical stability'' or ``main wind force 
resisting system''?
    Answer: For designing roof to wall, wall to floor and floor to 
chassis connections, the lateral and uplift design pressure 
requirements for Components and Cladding are to be used.
    13. 24 CFR 3280.305 (c)(1)(ii)--The following concerns the ``Table 
of Design Wind Pressures'' (``Table''):
    a. Do the footnotes for the ``Table'', such as no. 6 on shingle 
exemption, no. 7 the roof sheathing exemption, and no. 8 the exterior 
coverings exemption, also apply if method (A), using ANSI/ASCE 7-88, is 
used instead?
    b. Note 4 limits the ``Table'' to 10 degrees (nominal 2/12) minimum 
roof slope. Does this mean that they do not apply to a bowstring type 
roof?
    c. If a designer follows ANSI/ASCE 7-88 in method (A), can he 
ignore the prescriptive element of double trusses in the last 3 feet 
and have trusses designed accordingly?
    d. What are the uplift loads on a porch open on three sides? Are 
they different if the porch is only open on two sides (as on the end of 
a multi-section unit)? Do either of these porch configurations have the 
special 3-foot zones of increased wind pressure (or suction) the walls?
    e. Do each of the corners (looking at the plan view) of a double 
section unit with an offset section have the 3-foot zones as far as 
wall pressures are concerned, or do these zones only apply to the 
``outside'' corners? Or do these zones only apply to the intersections 
of the endwalls and sidewalls?
    f. Concerning bay windows, walk-a-bays, bow windows: do these 
experience the increased uplift on the roof? Do they count as part of 
the 3-foot roof zone?
    Answers: a. The footnotes on exterior coverings do not apply if 
Method (A) is used. All exterior coverings and fastenings must be 
completely designed for the design load provisions of ASCE 7-88.
    b. Truss configurations such as bow-string designs with slopes less 
than 10 degrees are not covered by the ``Table''.
    c. Yes.
    d. The uplift design pressures for a 3 sided open porch would be 
the same as for eaves or gables depending on their location (sidewall 
or endwall). A porch open on two sides at the end of multi-wide section 
would be designed for gable loads. Both of these configurations would 
also be required to be designed for the higher pressures in the 3'0'' 
Zones if located within 3'0'' of the corners.
    e. The 3'0'' regions apply to all corners including offset sections 
and all other conditions cited by the question.
    f. Bay windows, walk-a-bays and bow windows are part of the 3'-0'' 
roof zone unless they are significantly offset below the roof or the 
roof of the unit completely extends over those projections.
    14. 24 CFR 3280.305(c)(1)(ii)--In Zones II and III, under what 
conditions may a manufacturer meet Exposure B, ASCE 7-88? (e.g. when a 
home is permanently sited and the authority having jurisdiction 
verifies the Exposure B authenticity)?
    Answer: There are no conditions in Wind Zones II and III for which 
a home can be designed for Exposure B, ANSI/ASCE 7-88.
    15. 24 CFR 3280.305(c)(1)(ii)--In Alaska, which counties are in 
Zone III?
    Answer: There are no defined boundaries for Wind Zone III other 
than the 90 mph isotach in ANSI/ASCE 7-88 and identified in the Basic 
Wind Zone Map.
    16. 24 CFR 3280.305(c)(1)(iii)--There are many questions concerning 
recessed entries in Zones II and III if the ``Table'' is applied:
    a. Do the corners of a recessed entry have the 3 foot zones of 
higher cladding loads for walls?
    b. Does the soffit of a recessed entry experience a negative 
suction? If so, what is the value?
    c. Does the soffit of a recessed entry experience a positive 
pressure, acting upward? If so, what is the value? If so, is this 
upward pressure an additional load on the roof truss supporting the 
soffit, or is the truss loading still the same without the recessed 
entry?
    Answers: a. The corners of walls at recessed entries within 3'0'' 
of endwalls are to be designed for the 3'-0'' wall corner design 
pressures in the ``Table''. However, recessed entries which are more 
than 3'-0'' from the endwall and bounded on three sides need not be 
designed for the higher wall corner loads.
    b. Soffits of a recessed entry are to be designed as eaves or 
gables for the design pressures specified in the ``Table''.
    c. Soffits of recessed entries are to be designed for the eave or 
gable load requirements of the ``Table'' as positive pressures acting 
upward. For the recessed entry area, no additional design pressures are 
required for evaluation of roof trusses, other than the design 
pressures for eaves and gables as indicated in b. above.
    17. 24 CFR 3280.305(c)(2)(ii)--Table of Design Wind pressures--As 
indicated by Footnote #8, exterior coverings that are secured at 6'' 
o.c. to a \3/8\'' structural rated sheathing that is fastened to wall 
framing members at 6'' o.c. need not be evaluated for the design wind 
pressures shown in the ``Table''. We assume that the 6'' o.c. fastening 
schedule for both structural sheathing and exterior coverings are 
measured 6'' o.c. vertically along the studs. Please confirm this 
assumption.
    Answer: Footnote 8 requires fasteners to attach from the exterior 
covering to the structural sheathing at 6'' o.c. in both vertical and 
horizontal directions. However, fasteners need only be installed at 6'' 
o.c. from the structural sheathing to wall framing members (plates, 
studs, jamb studs, headers). For vertical wall and jamb studs the 
orientation of the 6'' o.c. spacing is in the vertical direction.
    18. 24 CFR 3280.305(c)(2)(ii)--``Table'' of Design Wind pressures--
What is the wind uplift value to be used for stud and jamb stud 
interaction calculations?
    Answer: The design uplift forces to be resisted by studs and jamb 
studs are the combined uplift loads from the ``Table'' for trusses 
(including corner loads from doubling of trusses), and any roof 
projections (eaves, gables, recessed areas, porches).
    19. 24 CFR 3280.305(c)(2)(ii)--``Table'' of Design Wind pressures--
The 6'' o.c. fastening requirement for exterior wall coverings, as 
indicated by footnote no. 8 under the ``Table'' of Design Wind 
Pressures on page 2470 of Federal Register, may pose some difficulties 
in some cases. For example, how can we fasten the \3/8\'' sheathing 
through vertical straps positioned at studs? Double penetration of 
straps will weaken its holding capability. The problem is compounded by 
the installation of a final exterior covering that must also be 
fastened based on 6'' o.c., somehow staggered to miss the \3/8\'' 
sheathing fasteners and the strap fasteners under the sheathing.
    Answer: Fasteners may be staggered at vertical straps to facilitate 
installation of wall and sheathing coverings and to avoid damage to the 
strapping material.
    20. 24 CFR 3280.306(d)--If over-the-roof ties are required, because 
that may be the only way to resist the load, it is not clear that 
diagonal ties would not be required at each vertical tie location along 
the mating line of multi section homes. This requirement needs further 
clarification.
    Answer: Diagonal ties need not be provided at each vertical over-
the-roof tie location along the marriage line of multiple section 
homes, if all design wind forces can be transferred across the mating 
line by the over-the-roof ties and site connections between the units 
specified in the manufacturer's instructions. Additional information on 
this subject is provided in our response to Question 26.
    21. 24 CFR 3280.305(e)(2) --A new prescriptive requirement for 
steel strapping for brackets to fasten walls to floors or roof trusses, 
shall have a maximum spacing of 24 inches on center for Wind Zones II 
and 16 inches on center for Wind Zone III. From a practical standpoint, 
the fasteners generally must be placed over studs. Where trusses are 
not aligned over studs, please confirm that stud-to-truss connections 
do not have to be direct, provided that indirect load transfers are 
substantiated.
    Answer: Trusses in homes designed for Wind Zones II and III must be 
aligned over studs for direct connection of the 26 gage metal strapping 
or brackets required by this section. Trusses may not be offset from 
studs except where they are added to provide reinforcement or as 
otherwise required by the design.
    22. 24 CFR 3280.305(e)(2)--We want to advise you that since nails 
will be driven mechanically through the 26-gage straps, their rejection 
may result in severe injuries to the operator. Therefore, we may have 
to pre-drill holes through straps and \3/8\'' sheathing and hand drive 
fasteners, or use a stronger gun and bigger fasteners.
    Answer: It would appear that it may be necessary to pre-drill holes 
or use larger sized guns or thicker fastener gages to penetrate the 26 
gage strapping materials.
    23. 24 CFR 3280.306(f)--Revised section 24 CFR 3280.306(d) requires 
manufactured homes designed for Wind Zones II and III have a 
supplemental vertical tie installed at each diagonal tie location. A 
written interpretation is needed to confirm the following:
    A. The connection of the vertical strap to the home should be 
designed for the vertical component of the manufacturer's calculated 
diagonal tie load (which corresponds with its anchorage instructions). 
The connection to the home is not required to be designed for 3,150 
pounds (4725 pounds ultimate). The vertical strap design on ``Table'' 
D2 of HUD's Regulatory Impact Analysis (RIA) agrees with this 
assumption. 10--#8 screws per strap calculates to approximately 
1,500 pounds per vertical tie.
    Answer: Connections of vertical ties to wall framing members need 
not be designed for the 3,150# working load requirements of the 
tie itself provided the fastening system and the member to which it is 
attached are capable of resisting the calculated design load imposed on 
the vertical tie.
    B: The connection of the vertical strap may be located at the I-
Beam, provided that the floor-to-frame connection is substantiated. In 
some designs this may be the preferred location (e.g. 5' o.c. diagonal 
tie spacing with a 6' patio door at sidewall).
    Answer: Vertical ties may be provided under the main chassis beams 
provided the design has considered the transfer of all loads assuming 
the vertical tie to be positioned under the I beam.
    24. 24 CFR 3280.306(f)--Since the Department will now require a 
vertical tie at each diagonal tie for Wind Zones II and III, how does 
HUD envision that ties will be properly secured to wall members so that 
the attachment point on the manufactured home is capable of resisting 
the tie allowable working load of 4,725 pounds?
    Answer: Vertical ties can be installed as continuous ties or 
connected to wall framing members by mechanical fasteners. Additional 
information on this subject is provided in our response to Question 23.
    25. 24 C.F.R. 3280.306(c)(2), (d) and (f)--Taken together 24 CFR 
3280.306(c)(2), (d) and (f) could mean that HUD staff anticipates over-
the-roof straps at each diagonal tie. If so, what is the purpose of 26-
gauge uplift straps and stronger trusses?
    Answer: Vertical ties are required to be positioned at each 
diagonal tie for gross stability against overturning. The ties between 
the roof and sidewall are required to resist the high localized uplift 
forces and to prevent roof system failures and separation from the wall 
system.
    26. 24 CFR 3280.306 (f) --Please also confirm that a diagonal tie 
is not required at each vertical tie, both on the perimeter and along 
the marriage wall.
    Answer: For anchoring systems used with multiple section units, 
vertical and diagonal ties may not be required at the marriage wall 
provided all wind forces can be designed to be transferred across the 
mating line without their use. However, diagonal and vertical ties are 
mandatory at the perimeter or exterior sidewall.
    27. 24 CFR 3280.306 (f)--We would also like permission to fasten a 
vertical tie at the I-beam, provided that the floor-to-frame connection 
is substantiated.
    Answer: Vertical ties may be provided under the main chassis beams 
provided the design has considered the transfer of all loads assuming 
the vertical tie to be positioned under the I beam.
    28. 24 CFR 3280.403(f), 404(f) and 405(f): The manufacturer is to 
specify at least one method of protecting exterior openings, without 
taking the home out of conformance with the standards. How does the 
Department envision that a manufacturer might take the home out of 
conformance with the standards when it designs exterior walls 
surrounding exterior openings to allow for the installation of shutters 
or protective covers?
    Answer: One example of how a home could be taken out of conformance 
with the Standards is to reduce the capacity of wall framing members 
due to excessive fastening patterns or large holes needed to install 
the shutters or protective covers.

    Dated: April 15, 1994.
Nicolas P. Retsinas,
Assistant Secretary for Housing-Federal Housing Commissioner.
[FR Doc. 94-9689 Filed 4-18-94; 3:36 pm]
BILLING CODE 4210-27-P