Manufactured Home Construction and Safety Standards: Metal Roofing; Interpretative Bulletin I-2-98

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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