[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]
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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.
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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