[Federal Register Volume 63, Number 91 (Tuesday, May 12, 1998)]
[Rules and Regulations]
[Pages 26386-26389]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-12341]
[[Page 26385]]
_______________________________________________________________________
Part VI
Department of Housing and Urban Development
_______________________________________________________________________
24 CFR Part 3280
Manufactured Home Construction and Safety Standards: Metal Roofing;
Interpretative Bulletin I-2-98; Final Rule
Federal Register / Vol. 63, No. 91 / Tuesday, May 12, 1998 / Rules
and Regulations
[[Page 26386]]
DEPARTMENT OF HOUSING AND URBAN DEVELOPMENT
24 CFR Part 3280
[Docket No. FR-4271-N-01]
RIN 2502-AH05
Manufactured Home Construction and Safety Standards: Metal
Roofing; Interpretative Bulletin I-2-98
AGENCY: Office of the Assistant Secretary for Housing--Federal Housing
Commissioner, HUD.
ACTION: Interpretative Bulletin.
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SUMMARY: In January 1994 HUD amended the Manufactured Home Construction
and Safety Standards to improve the resistance of manufactured homes to
wind forces in areas prone to hurricanes. In part, the amendments
provided that manufactured homes designed to be sited in high wind
areas must be designed to resist either the design wind loads in a
specified industry performance standard or alternative wind pressures
set out in a prescriptive Table included in the regulations. Some
questions have arisen concerning: Whether manufacturers that design
their products using the wind pressures in the Table must provide roof
sheathing under metal roofing; and the appropriateness of the testing
of metal roofing that has been done. Therefore, the Department finds it
necessary to reiterate, through this Interpretative Bulletin (IB), its
current policy with regard to the regulations. A related advance notice
of proposed rulemaking is published elsewhere in today's Federal
Register.
DATES: Effective Date: May 12, 1998.
FOR FURTHER INFORMATION CONTACT: David R. Williamson, Director, Office
of Consumer and Regulatory Affairs, Department of Housing and Urban
Development, 451 Seventh Street, SW, Room 9156, Washington, DC 20410,
telephone: (202) 708-6401 (this is not a toll-free number). For
hearing-and speech-impaired persons, this number may be accessed via
TTY (text telephone) by calling the Federal Information Relay Service
at 1-800-877-8339.
SUPPLEMENTARY INFORMATION: In this Interpretative Bulletin (``IB'') HUD
clarifies the meaning of the standard in 24 CFR 3280.305(c)(1)(ii)(B)
as applied to metal roofing. Under this provision, elements of
manufactured homes that are designed for high wind areas currently must
be designed to resist wind pressures prescribed in a Table of Design
Wind Pressures (``Table''). (Alternatively, under
Sec. 3280.305(c)(1)(ii)(A), the design may be qualified using general
performance standards that utilize the design wind loads in ANSI/ASCE
7-88; this IB does not affect the option to use those performance
standards.) This IB is issued pursuant to 24 CFR 3280.9 and 3282.113.
HUD has received requests from manufacturers and Design Approval
Primary Inspection Agencies (DAPIAs) for clarification of design and
testing requirements for metal roofing in wind zones II and III under
the provisions in Sec. 3280.305(c)(1)(ii)(B). Because these
requirements are not being applied uniformly by DAPIAs and
manufacturers, and HUD agrees with industry representatives that the
regulation needs clarification, the Secretary has determined that the
public's interest in the manufacture of housing that is safe for the
conditions under which the housing is sited would best be served by the
issuance of this IB. Issuance of the IB also is in the interest of
competitive fairness to members of the industry. This IB does not
denote any change in policy or interpretation formulated by HUD, but
clarifies requirements that were adopted as part of an extensive
notice-and-comment rulemaking process.
Therefore, because of the need for resolution of any question
regarding the requirements applicable under the Manufactured Home
Construction and Safety Standards (``standards'') to metal roofing in
wind zones II and III, and the fact that this is not a change in the
position or policy of the Department, in accordance with 24 CFR
3282.113, the Secretary has deemed it not to be in the public interest
to issue the interpretation for public comment under 24 CFR part 3282,
subpart C.
The Department understands, however, that there may be concerns
about the requirements or implementation of roofing standards for
manufactured homes sited in high-wind areas. In that regard, persons
interested in recommending any changes to the policy clarified in this
IB are directed to the advance notice of proposed rulemaking published
elsewhere in today's Federal Register.
Background
The manufactured housing construction standards in 24 CFR
3280.305(c)(1)(ii) for wind zones II and III were established by HUD in
a rule published on January 14, 1994 (59 FR 2469) (``January 1994
rule''). It is clear from the history of this rule, which amended the
Federal Manufactured Home Construction and Safety Standards in 24 CFR
part 3280 to improve the resistance of manufactured homes to wind
forces in areas prone to hurricanes, that HUD was intending to create
prescriptive standards that manufacturers could elect to comply with as
an alternative to the general performance standards that utilize the
design wind loads in ANSI/ASCE 7-88. In particular, the January 1994
rule provided that each manufactured home designed for wind zones II or
III must be designed to resist either the design wind loads in ANSI/
ASCE 7-88 or the wind pressures specified in the Table.
A question has been raised concerning whether manufacturers that
design their homes using the wind pressures in the Table must provide
roof sheathing under metal roofing to meet the requirement for
resisting the wind pressures specified for roof coverings in the Table.
Although the preamble of the January 1994 rule does not address the
issue of metal roofing and roof sheathing directly, there is ample
evidence of HUD's objectives in establishing the higher wind standards.
The January 1994 rule clearly reflects HUD's intent to provide, through
the prescriptive Table, an option that would provide comparable
rigidity (``a rigid box''),1 as an alternative to designing
manufactured homes using the design wind loads of ANSI/ASCE 7-88. This
intent also is consistent with the statement in Sec. 3280.301 that
subpart D of 24 CFR part 3280, which includes Sec. 3280.305, is
intended ``to assure that the manufactured home will provide: (a)
Structural strength and rigidity * * *.''
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\1\ Note, i.e., the option of using the Table would provide
structural performance within permissible deflection limits.
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The January 1994 Rule
Although it is more prescriptive than the ANSI/ASCE 7-88
performance standard, the Table allows manufacturers to use alternative
materials for the roof structure as long as those materials, and the
entire manufactured home, meet the requirements in the
Table.2 In explaining the need for the January 1994 rule,
HUD noted that storm damage to manufactured housing is primarily in the
form of roof failure, loss of roof diaphragm material, connection
failures, and tiedown/foundation failures. HUD also noted that in
Hurricane Andrew, manufactured homes ``became dangerous flying
missiles, inflicting more property damage on neighboring
[[Page 26387]]
structures.'' (See 59 FR at 2457, ``Problem to be Addressed.'') In the
``Summary'' in the preamble of the January 1994 rule, HUD stated: ``The
revised standard also requires exterior roof and wall coverings to be
fastened adequately to sheathing and framing members, to resist higher
design wind pressures. The purpose of this rule is to increase the
safety of manufactured homes, thereby reducing deaths and injuries and
extensive property damage losses in areas where wind-induced damage is
a particular hazard and risk.'' (59 FR at 2456.)
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\2\ One kind of roof design, which is specified in footnote 7 of
the Table, has been deemed to meet the performance requirements of
the Table without the need for additional engineering analysis or
load tests.
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Also in the preamble, HUD related that ``[a]mong the major
deficiencies contributing to manufactured housing damage in Hurricane
Andrew were inadequate connections between exterior roof or wall
coverings and supporting sheathing or framing and between walls, roofs,
and floors'' (59 FR at 2458, ``Field Investigations''). This portion of
the preamble continues:
In particular, losses of roof coverings were widespread, and
were considered by some to be the first mode of failure for
manufactured homes damaged in Hurricane Andrew. Other roof-related
damage was due to loss of sheathing, failure of connections, or a
combination of these problems * * *
* * * Metal or plastic siding used in manufactured housing was
readily damaged or penetrated by flying debris during the high winds
in Hurricane Andrew. Loss of roof or wall cladding allows the
building to be penetrated by the weather and has far-reaching
consequences beyond the area of envelope integrity.
* * * In addition, failure of coverings or attachments to the
manufactured home structure also caused missile-type damage to other
homes.
* * * Edges and corners of roofs and endwalls of manufactured homes
appeared to have been particularly vulnerable to the high wind forces,
according to the damage typically reported in these areas * * * (59 FR
at 2458)
Later in the preamble, these same themes were sounded. For example:
``Commonly observed failures included loss of roof membranes and blow-
off of roof sheathing * * *.'' (59 FR at 2458.)
HUD also cited a Federal Emergency Management Agency (FEMA) report
on the damage in Hurricane Andrew:
It was observed that the breakup of corrugated metal siding and
roofed buildings such as manufactured homes and pre-engineered metal
frame buildings contributed significantly to the generation of
airborne debris. This was evident from debris damage to nearby
downwind structures.
(59 FR at 2462, ``Cost Considerations'').
HUD did state its expectation that the manufactured housing
industry would be innovative in developing designs, components, and
construction techniques that meet the standards but maintain the
affordability of manufactured homes. It was clear, however, that the
final product would be expected to perform at an acceptable level. In
fact, HUD's stated intent was to strengthen the requirements for
structural assemblies, components, connectors, fasteners, and a number
of other areas so that the manufactured home would be able to resist
the same wind forces as required for site-built and modular housing.
(59 FR at 2467.)
HUD also notes that the economic analysis prepared by an industry
trade association factored into the predicted costs of compliance with
HUD's higher wind standard proposals the cost of roof
sheathing.3 Therefore, the indications are that the industry
itself, at the time the rule was being developed, understood that the
requirement was for a rigid box.
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\3\ See attachments to the comments submitted by the
Manufactured Housing Institute (commenter #112 in Docket #FR-3380)
on the proposed rule that was finalized in the January 1994 rule.
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Finally, in summarizing the changes made by the January 1994 rule
to Sec. 3280.305(c), the preamble states that:
Exterior roof and wall coverings (excluding glazing), sheathing,
and fastenings need not be evaluated for the design pressures
specified by the Table, when fastened to a 3/8'' structural rated
sheathing and the sheathing is oriented and secured to framing
members in accordance with the fastening schedule specified in the
Table. (59 FR at 2467.)
An IB that was published by HUD in the Federal Register on July 1,
1994 (59 FR 34294), further bolsters the intent of the January 1994
rule. In that IB, HUD recognized that metal siding (such as vertical
steel siding) could, under strict circumstances, be approved as both a
structural wall sheathing and an exterior covering material. The strict
circumstances specified in the IB ensured that the metal siding/
exterior covering would, in effect, maintain a rigid box, including
covering and fastening requirements, and would resist the full design
pressures specified in the Table. The same reasoning applies to metal
roofs in Wind Zones II and III in this IB.
Subsequent Testing of Metal Roofs
In reviewing tests performed under the higher wind standards on
metal roof systems without sheathing, the Department has found that
none of the tests satisfied all of the requirements of the standards.
The test methods used introduced additional resistance for the test
assemblies that would not be available under actual conditions of
application or construction, contrary to the requirements of
Sec. 3280.303(c). The test methods also did not consider the combined
effect on fasteners and components of horizontal wind forces, nor the
compression load added as a result of the sole use of metal roofing
without sheathing. The tests also did not measure deflection, as
required under Sec. 3280.401 and as would be necessary to ensure
compliance with Secs. 3280.305 (a) and (h).
Other specific questions about the tests include:
Concerns about whether the laboratory tests simulated
factory conditions for replicating the workmanship associated with the
small edge distance and installation of the large number of fasteners
required;
The ability of the quality control system to prevent
production problems that would be caused because of the large number of
fasteners required and the small edge distance for the outermost row of
fasteners at the metal-to-rim rail connection of the roof, which is
likely to cause damage to wood rim members or tearing of the metal
during production or when design wind loads are applied;
Failure of the tests to include all of the fasteners
required in actual production, which would have further damaged the rim
rail and weakened the tested assemblies; and
Lack of information about deformation criteria for the
connectors (fastener slip) or other conditions that would constitute
failure of the test assembly, such as rim rail rotation.
Accordingly, under the authority of 42 U.S.C. 3535(d),
Interpretative Bulletin I-2-98 is issued by the Department as follows:
Note: HUD Interpretative Bulletin I-2-98 will not appear in the
Code of Federal Regulations.
Interpretative Bulletin I-2-98--Manufactured Home Construction and
Safety Standards: Metal Roofing (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 is
authorized to establish, amend, and revoke by order appropriate Federal
manufactured home construction and safety standards (``standards''). On
January 14, 1994 (59 FR 2456), HUD published certain changes to the
standards for high wind areas, as codified in 24 CFR part 3280.
Subsequently, HUD has published interpretations of the January 1994
rule at 59 FR 19072 (April 21, 1994) and 59 FR 34294 (July 1, 1994). In
the April 21,
[[Page 26388]]
1994, Interpretative Bulletin, HUD indicated that it may issue
additional Interpretative Bulletins to provide further assistance in
the implementation of the new standards. This Interpretative Bulletin
I-2-98 1 is issued to clarify requirements applicable to the
use of metal roofing in wind zones II and III. All section references
are to sections of 24 CFR part 3280.
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\1\ This designation indicates that this is the second
interpretive bulletin issued in 1998. The interpretive bulletin
issued on February 18, 1998 (63 FR 8330) was not officially
designated as I-1-98 because it was an amendment to an earlier
interpretative bulletin designated as J-1-76.
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HUD interprets Sec. 3280.305(c)(1)(ii)(B) to require every design
for manufactured housing for high wind areas to include roof sheathing
or alternative roof material that performs like sheathing in resisting
the wind pressures specified in the Table of Design Wind Pressures
(``Table''), whenever the Table is used as the basis for qualifying the
design. The phrase ``performs like sheathing'' means that the roofing
system will transfer the higher wind loads to which the Table is
formulated to structural support members and components without
compromising the integrity of those members and components to such an
extent that they cannot resist the applicable design pressures
specified in the Table.2 In developing the Table, HUD
contemplated a design that utilizes structural rated roof sheathing
that is at least \3/8\ of an inch thick and is installed in accordance
with footnote 7. If roof sheathing is not used in the design for the
roof system, in accordance with Sec. 3280.303(c) load tests or
engineering analyses used to determine that the manufactured home
complies with the Table must account for the additional high-wind loads
transferred to other parts of the structure because of the absence of
separate load-resistant sheathing. Thus, metal roofs without sheathing
may be used if they are strong enough to perform like sheathing and can
meet all of the requirements discussed in this paragraph.
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\2\ In order for the metal roof to resist the uplift loads
applicable in Wind Zones II and III and transfer the design loads,
the Department expects that the metal roof would be fastened to the
support members (trusses, edge members, etc.).
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When separate sheathing is utilized in a design, the sheathing must
be shown to be capable of resisting the wind pressures specified for
sheathing in the Table, unless the sheathing is structural rated roof
sheathing that is at least 3/8 of an inch in thickness and is installed
and secured as provided in footnote 7 of the Table. A manufacturer that
includes in its design sheathing that complies with the specifications
set out in footnote 7 can avoid having to substantiate the sheathing as
being in compliance with the loading requirements for sheathing in the
Table. In both of these cases, however, all other loading requirements
in the Table and requirements of the standards would still have to be
met.
Of course, manufacturers continue to have the additional option,
set forth in Sec. 3280.305(c)(1)(ii)(A), to design any manufactured
home, including the roof (metal or nonmetal), using the design wind
loads for Exposure C as specified in ANSI/ASCE 7-88 and the applicable
design wind speed.
Testing Protocols
To be acceptable under the standards, all roofs, including metal
roofs, must be designed using either engineering analysis or suitable
load testing protocols, in accordance with Sec. 3280.303(c). Until the
higher standards were adopted for wind zones II and III, metal roofs
for manufactured homes generally had been qualified using engineering
analysis. Manufacturers have chosen to test metal roofs intended for
wind zones II and III using the design wind pressures in the Table,
apparently because the metal roofs may not have been able to qualify
under the higher standards through engineering analysis.
The regulations set forth a series of requirements regarding
testing. Under Sec. 3280.303(c), if the strength and rigidity of a unit
or component is to be determined by testing, the load tests must
replicate the actual loads and conditions of application, not just
approximate those loads and conditions. A manufacturer relying on
Sec. 3280.401 to establish the acceptability of a compliance
alternative also must meet all of the requirements established in that
section. Section 3280.401(b), for example, requires that deflection
measurements be taken.3 Further, if a manufacturer cannot
perform an engineering analysis to demonstrate compliance with the
Sec. 3280.305(h) design requirements for roofs and the Sec. 3280.305(c)
design requirements for systems, components, and framing, the
manufacturer must comply fully with established testing protocols or
obtain HUD approval of special testing under Sec. 3280.303(g).
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\3\ This concern with deflection measurements, and the concept
of a sound structural frame, are also seen in Sec. 3280.305(h),
which specifically requires that roofs be of sufficient strength to
withstand the load requirements in Sec. 3280.305(c) without
exceeding established deflections, and in Sec. 3280.305(a), which
states:
Each manufactured home shall be designed and constructed as a
completely integrated structure capable of sustaining the design
load requirements of this standard, and shall be capable of
transmitting these loads to stabilizing devices without exceeding
the allowable stresses or deflections* * * .
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Section 3280.303(g) allows for the development of special testing
procedures that demonstrate structural properties and significant
characteristics when there is no recognized or suitable testing
procedure. In the absence of an established suitable testing protocol,
a manufacturer that wants to establish compliance with a standard
through testing must submit the testing protocol to HUD for approval.
HUD would anticipate that such a protocol would address test set-up,
loading apparatus, and size and dimensions of the test assembly, and
would establish failure criteria. Section 3280.303(g) places the burden
on manufacturers for developing such testing procedures to demonstrate
structural properties and significant characteristics of a material,
assembly, component, or member.
Summary of Requirements, Using Table
Because there has been confusion about the requirements of the
regulations in question, HUD will allow a grace period of 30 days after
the date of publication of this IB for compliance with the requirements
as clarified in this IB. Thus, in qualifying any roof through testing,
HUD will not recognize as being in compliance with the requirements of
the Table a metal roof system that is installed on any unit for which
the manufacturing process is completed beyond the grace period, unless
that metal roof system is able to resist the appropriate wind pressures
specified in the Table and complies with at least one of the following
conditions:
(1) The metal roofing is a covering, which is designed to resist
the applicable wind pressures specified for roof coverings in Table and
is installed in conjunction with structural rated roof sheathing that
is at least \3/8\ of an inch in thickness and is fastened as provided
in footnote 7 of the Table;
(2) The metal roofing is a covering, which is designed to resist
the applicable wind pressures specified for roof coverings in Table and
is installed in conjunction with roof sheathing that does not qualify
as acceptable automatically under footnote 7 in the Table, but that has
been qualified through engineering analysis or appropriate testing
procedures as capable of resisting the wind pressures established for
roof sheathing in the Table; or
(3) The metal roof itself has been tested, using procedures that
either meet all of the requirements of Secs. 3280.303(c)
[[Page 26389]]
and 3280.401 (or another suitable load test) or have been developed and
approved in accordance with Sec. 3280.303(g), and the metal roof has
been determined to perform like sheathing by transferring the higher
wind loads to structural support members and components without
compromising the integrity of those members and components to such an
extent that they cannot resist the applicable design pressures
specified in the Table.4
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\4\ See footnote 2, above.
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As noted, in the absence of recognized testing procedures, a
manufacturer may develop and submit to HUD for approval, in accordance
with Sec. 3280.303(g), a testing procedure that would demonstrate the
requisite structural properties and significant characteristics of the
alternate design or material.
Authority: 42 U.S.C. 3535(d) and 5424.
Dated: April 29, 1998.
Art Agnos,
Acting General Deputy Assistant Secretary for Housing.
[FR Doc. 98-12341 Filed 5-11-98; 8:45 am]
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