Source: https://www.federalregister.gov/documents/2013/01/18/2013-01066/manufactured-home-construction-and-safety-standards-test-procedures-for-roof-trusses
Timestamp: 2018-07-16 09:25:15
Document Index: 267625887

Matched Legal Cases: ['§\u20093280', '§\u20093280', '§\u20093280', '§\u20093280', '§\u20093280', '§\u20093280', '§\u20093280', '§\u20093280', '§\u20093280']

4060-4070 (11 pages)
HUD's Further Modifications to MHCC's Proposed Revision to § 3280.402(d)(3)
https://www.federalregister.gov/d/2013-01066 https://www.federalregister.gov/d/2013-01066
In 2002, MHCC began considering revisions to the Construction and Safety Standards and, in 2003, recommended revisions to the current requirements for roof truss testing.[1] Those recommendations were included in HUD's proposed rule to amend the Construction and Safety Standards, published in the Federal Register on December 1, 2004 (69 FR 70016). After considering public comment received on the proposed rule, HUD returned the proposal on truss testing procedures to MHCC. As indicated in the preamble of HUD's final rule published in the Federal Register on November 30, 2005 (70 FR 72024), which followed the December 1, 2004, proposed rule, HUD stated that truss testing procedures are too important a safety consideration to leave unaddressed. In returning the rule, HUD also stated that the standards had not been modified in a number of years and needed to be examined to determine whether they were adequate to protect homeowners in all geographic areas of the country. HUD's review of damage assessments following Hurricane Charley reinforced its conclusion regarding the need for the MHCC to ensure that truss testing procedures were updated and adequate to protect homeowners from roof and structural damage accompanying high wind events.
HUD requested MHCC to work expeditiously to reevaluate and resubmit new proposals for truss testing procedures. As a result, the Truss Test Task Force of MHCC's Standards Subcommittee was established. Five teleconferences of this task force were held, and the full MHCC held two teleconferences to review and vote on new truss testing procedures. HUD worked closely with MHCC throughout the review and reevaluation process, and agreed with the majority of the proposals to strengthen the truss testing procedures made by MHCC, but made editorial revisions and modified the Start Printed Page 4061MHCC's proposal on uplift testing. Those recommendations and modifications were included in a proposed rule published in the Federal Register on June 16, 2010 (75 FR 34064). After careful review of the public comments received in response to the proposed rule, HUD made additional editorial and other revisions and further modified the MHCC's proposal regarding uplift testing. HUD's additional revisions in response to public comment are reflected in this final rule.
Proof Load: 1.75/12 hours or Ultimate Load: 2.5/5minutes. Proof Load: 1.75/12 hours or 2.0/6 hours or Ultimate Load: 2.5/5minutes.
Wind Uplift Loads Wind Uplift Loads
* Wind Zone I: 1.75/3 hours—inverted. Wind Zone I: 2.50/1 minute—inverted.
* Wind Zone I: 1.75/3 hours—upright. Wind Zone I: 1.75/1 minute—upright.
* Wind Zones II/III: 1.75/3 hours —inverted. Wind Zones II/III: 2.0/1 minute—inverted.
* Wind Zones II/III: 1.75/3 hours—upright. Wind Zones II/III: 1.75/1 minute—upright.
* Note—The previous standards do not specify either the inverted or upright uplift load test method. Therefore, either method was acceptable under the existing standards and most roof truss designs were certified using the inverted/nonconservative roof truss testing procedure.
Question 1: Under the proposed rule, the proof load test or the ultimate load test can be used to qualify trusses in high snow load areas. Should the more stringent and reliable ultimate load test procedure be required only to qualify roof trusses designed for use in high snow load areas, such as the North and Middle Roof Load Zones, where the risk of roof and truss failure is greater?Start Printed Page 4062
Comment: The commenters indicated that HUD should maintain the option to use either test method in all roof load zones and that HUD should not adopt different requirements for North and South roof load zones because of past performance history of roof trusses in high snow load areas.
After considering the issues raised by the commenters and HUD's own evaluation of issues related to this final rule, HUD is making the following specific changes to the June 16, 2010, proposed rule and current roof truss testing requirements in § 3280.402 of the Construction and Safety Standards.
1. In § 3280.402(a), upon the effective date of the rule, testing procedures will be required for new roof truss designs in all three wind zones and for existing truss designs used in high wind areas (Wind Zones II and III).
2. In § 3280.402(d)(1), the proof load test (formally known as the non-destructive test procedure) contains both the proposed test method (2.0 times the design live load for 6 hours) as well as the existing non-destructive test method (1.75 times the design live load for 12 hours). Three consecutive tests of truss assemblies made with average quality materials and workmanship must meet all acceptance criteria, including new deflection limits for dead load, in order for the truss design to be acceptable.
3. In § 3280.402(d)(2), the ultimate load test procedure (2.5 times the design live load for 5 minutes) requires that two consecutive tests of truss assemblies made with average quality workmanship and materials meet all acceptance criteria, including new deflection limits for dead load, in order for the truss design to be acceptable.
4. In § 3280.402(d)(3), the final rule requires that for new truss designs to be used in Wind Zone I, when deemed necessary by a Professional Engineer or Registered Architect, at least one truss must meet all acceptance criteria and sustain 2.5 times the net design uplift load (22.5) for the inverted test procedure or 1.75 times the design uplift load (15.75) for at least 1 minute. For Wind Zone I, this results in an increase in the factor of safety from 1.75 to 2.5 for trusses tested for uplift in the inverted position, maintains the current factor of safety for uplift testing at 1.75 for trusses tested in the upright position, and reduces the period of overload testing from 3 hours to 1 minute for both test methods. For roof trusses designed to be used in Wind Zones II and III, both the currently utilized inverted test method and new upright test method may be used for conducting the wind uplift load test. However, there are different factors of safety and the number of tests required for each test procedure. For the inverted test method (load applied to the bottom chord of the truss), three consecutive tests must meet all acceptance criteria and sustain at least 2.0 times the design uplift load for 1 minute. For the upright test method (load applied to the top chord of the truss), two consecutive tests must meet all acceptance criteria and sustain 1.75 times the design live load for 1 minute.
5. In § 3280.402(e), the follow-up testing procedures and in-house quality control program requirements have been clarified for both manufacturers of roof trusses and for home manufacturers producing roof trusses for their own use. In addition, one truss test is to be conducted after the first 100 trusses have been produced, with a subsequent test for every 2,500 trusses qualified by either the proof load test procedure or by the inverted test procedure. One truss test will also be required for every 4,000 trusses produced, for trusses qualified under the ultimate load procedure or the upright uplift test procedure.
Based on the review of comments received from the public, HUD is further modifying the recommendation from MHCC on uplift testing, because MHCC's overload provisions for uplift load tests in the inverted position were deemed to be too conservative. HUD Start Printed Page 4063now agrees with MHCC that either test method, inverted or upright, should be permitted to evaluate uplift resistance of trusses designed to be used in Wind Zones II and III. However, this final rule requires that three consecutive trusses be successfully tested utilizing an overload factor of safety of 2.0 for trusses evaluated using the inverted test method. HUD's modification for upright testing is based in part on the findings of a study conducted by the National Association of Home Builders Research Center (NAHB-RC), “Comparison of Methods for Wind Uplift Load Testing of Roof Trusses for Manufactured Housing,” and the requirements of the National Fire Protection Association (NFPA) consensus process related to uplift testing. In particular, the NAHB-RC study found that trusses tested in the inverted position failed at higher loads, had smaller mid-span deflections, and experienced different fail modes than trusses tested in the upright position. This is because the difference in truss orientation results in the uplift load being applied by pulling up on the top chord of the truss in the upright position (in the manner in which the wind would apply load to the trusses), while, in the inverted position, the uplift load is applied by pushing down on the bottom chord of the truss.
HUD estimates that there are approximately 150 truss designs in use for Wind Zones II and III, and that the cost of retesting, recertifying, and redesigning the truss designs will cost producers approximately $500 per truss design. As a result, the total cost of retesting, re-certifying, and redesigning truss designs for Wind Zones II and III is assessed to be $75,000 based on current production levels of 4,620 shipments.Start Printed Page 4064
In order to meet the testing standards provided by this final rule, HUD expects that 75 percent of the designs currently used for Wind Zones II and III will require modification. The increased construction cost to meet the new standards is estimated at $1.00 per truss. Based on an average of 51 trusses per transportable section in Wind Zones II and III, and 1.64 transportable sections per home, the annual increase in truss construction costs total $289,170 (7,560 transportable sections * 51 trusses per section * $1.00 increase in production cost * 75 percent of trusses produced). Over a 30-year period, the discounted value of the increase in production costs total $4.8 million, assuming a 7 percent discount rate, or $7.4 million, assuming a 3 percent discount rate.
Based on 2008 housing data from the U.S. Postal Service [2] and the Census Bureau's Survey of Manufactured Housing, newly shipped manufactured housing accounts for 0.076 percent of the total housing stock in states prone to hurricane strikes. An approximation of the damage occurring to manufactured housing totals $836,634 ($1,194,4 million * 0.076 percent). The discounted value of the annual damage over 30 years is $11.1 million, assuming a 7 percent discount rate, or $16.9 million, assuming a 3 percent discount rate. The higher standards resulting from the tests required by this final rule would prevent a portion of this damage, although the annual variability in the number and strength of high wind events makes it difficult to provide a precise estimate. In order for the benefits to exactly offset the costs imposed by this rule, 44 percent of the damage would need to be prevented This percentage should not be considered a maximum, as it does not include damage from other types of weather events, such as heavy snowfall, or prevented deaths, which is also discussed below.
The Regulatory Flexibility Act (RFA) (5 U.S.C. 601 et seq.) generally requires an agency to conduct a regulatory flexibility analysis of any rule subject to notice and comment rulemaking requirements, unless the agency certifies that the rule will not have a significant economic impact on a substantial number of small entities. This rule would regulate establishments primarily Start Printed Page 4065engaged in making manufactured homes under North American Industry Classification Standard (NAICS) 32991. The Small Business Administration's size standards define as small an establishment primarily engaged in making manufactured homes if it does not exceed 500 employees. Of the 123 manufactured home operations included under this NAICS definition, 55 are small manufacturers that fall below the small business threshold of 500 employees. The rule would apply to all of the manufacturers and would, therefore, affect a substantial number of small entities. For the reasons stated below, HUD knows of no instance in which a manufactured home manufacturer with fewer than 500 employees would be significantly affected by this rule.
2. Revise § 3280.402 to read as follows:
Start Printed Page 4067
(vi) Final recovery phase. Remove 2.5 times the design live load but not the Start Printed Page 4068dead load. Measure and record deflections within 4 hours after 2.5 times the design live load has been removed.
(ii) Wind Zones II and III uplift loads test. This test is required for all trusses designed for use in Wind Zones II and III. A minimum of three average quality/consecutive uplift load tests are to be conducted for each truss design when tested in the inverted position and a minimum of two average quality/consecutive uplift load tests are to be conducted for trusses in the upright position. The trusses must pass all requirements of the test for initial qualification of the truss design. The uplift load for trusses designed to be used in Wind Zones II and III for the clear span or eave cornice projections is to be determined by subtracting the dead load applied to the truss from the uplift load provided in the Table of Design Wind Pressures in § 3280.305(c)(1)(ii)(B).
(ii) Those home manufacturers producing trusses for their own use, and which are not listed or labeled, must have an in-house quality control program (see paragraph (i) of this section) that includes follow-up testing, as specified in this section, and is Start Printed Page 4070approved by their Design Approval Primary Inspection Agency (DAPIA).
2. See http://www.huduser.org/​datasets/​usps.html.