Wednesday, December 4, 2013

It's Almost Here! New HUD Roof Truss Testing Procedures

The deadline is fast approaching for HUD home manufacturers to start using roof trusses that meet the new requirements of 24 CFR 3280.402. The document was approved on Jan. 18, 2013, and becomes effective Jan. 13, 2014.
We’re on it
At NTA, we’ve has been working with our roof truss manufacturing clients over the past year to make sure their roof trusses meet the new requirements in time to supply HUD homemanufacturers. When you consider that all wind zone II and III roof trusses have to be requalified, the scope of the changes are pretty epic. Luckily, existing wind zone I roof trusses were grandfathered in. 
Let’s review the changes
The changes in 24 CFR 3280.402 fall into three basic categories:
1. Test procedures
2. Test criteria
3. Quality system
Test procedure changes
The test procedure changes start with the names of the procedures, but also include loading and load duration changes.
o   The old ‘non-destruct’ test procedure is now called a ‘proof load’ test.
o   The old ‘destruct’ test procedure is now called an ‘ultimate load’ test. 
The old test procedures specified applying loads 12 inches on center to simulate uniform loading. The new procedures have diagrams showing load points 6 inches on center. Due to a criteria change, the overhang deflection must be measured during the tests.
The non-destruct test required that 1.75 times the live load be maintained for 12 hours. The proof load procedure calls for the same or, by increasing the safety factor to 2 times the live load, the time can be reduced to 6 hours.
 Despite its name, the destruct procedure didn’t require destroying the roof truss if 2.5 times the live load could be held for 5 minutes. At that point, the test could be stopped. The ultimate load procedure is similar, but after the roof truss maintains the required load, there’s a recovery phase where deflection is measured no more than 4 hours after the load’s been removed.
Uplift testing can be performed with the roof truss in either an upright or inverted position. With the old procedure, the maximum load was 1.75 times the design uplift load held for 3 hours. With the new procedure, upright testing is the same, but inverted testing uses 2.5 times the load for wind zone I, and 2 times the load for wind zones 2 and 3. However, the new procedure only requires holding the load for 1 minute.
Test criteria
The test criteria have changed due to the afore-mentioned increase to the safety factors for the inverted position uplift testing and to the new requirement on overhang deflections.
Quality system
The new program is much more specific about quality system requirements than the old program. The quality control program must address, at a minimum, but is not limited to:
1. Lumber quality
o   Material grade
o   Allowable splits or knots            
2. Workmanship
o   Plate placement and embedment tolerances
o   Other manufacturing tolerances
3. Calibration of equipment
4. Follow-up testing
5. Procedures in the event of non-complying test results
At NTA, our standard quality system requirements already addressed these new HUD requirements, but it’s good to know they’ll be more uniformly addressed across the industry moving forward. 
A closer look at follow-up testing
All trusses qualified under 24 CFR 3280.402 are now subject to a follow-up testing program. Because the code text is a little vague on the subject, we engaged in communications and discussions with HUD and Manufactured Housing Institute (MHI), and determined this requirement includes the grandfathered-in wind zone I roof trusses. The test frequency depends on the type of testing that was initially performed: 
o   Proof load qualified roof trusses and inverted uplift qualified roof trusses must be tested within the first 100 trusses and after every 2500 trusses, or every 6 months, whichever comes first. 
o   Ultimate load qualified roof trusses must be tested after every 4000 trusses, or every 6 months, whichever comes first. Additionally, if a roof truss hasn’t been produced within 6 months, as soon as one is, it needs to be tested, even though the standard count hasn’t been reached.
The takeaway
On Jan. 13, 2014, if you’re a HUD home manufacturer, you need to be using roof trusses qualified under the requirements of 24 CFR 3280.402, and if you’re a roof truss manufacturer, you need to be supplying your clients with properly certified roof trusses. 

As a leader in the HUD industry, NTA has a fully developed program to help you test and certify your roof trusses to meet the new requirements. To learn more about what we're doing right now, read the press release. If you need assistance or want more information, contact us today.

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