Performance

The Gypsum Association “Fire Resistance Design Manual” (GA-600-12) lists file RC2601 with two layers of 5/8 in. gypsum wallboard (GWB) on wood joists.

We recently received bids on a school project, which referenced UL P523. This assembly used light-gauge steel trusses. We noted on the drawing that we could accept an alternate design using wood trusses in lieu of light-gauge steel framing, if the alternate design could meet the fire ratings.

Are there any typical wood truss span tables for roofs and floors available? Standard framing details for use in preliminary design?

We have a customer that bought trusses in June. The trusses were shipped [ and one month later are] being set. The chords have weathered and bowed. What is the industry standard for dealing with this problem? What is our liability in this situation? We were not aware of any delays on the customer’s part and shipped as requested. Note: These trusses are 62 ft. scissor trusses.

I need to obtain some information on fire-retardant-treated roof trusses.

Are there any schematics available on how to horizontally brace a 7/12 pitch roof?

Is lag bolting the bottom chord of a truss to the top plate of a wall a proper fix to correct truss arching, assuming the attic is properly vented?

Are there any associations that have recommendations for the installation of wood trusses?

Some building designers believe that gable end webs need to be L-braced to 90% of the web length, which sounds fine. However, they spec that scissors gable end webs need to be braced to 100% of the web length. That means that in the field they are notching the braces to fit around top and bottom chords – you can imagine how difficult that can be. Is that necessary or even the intent of the web L-bracing?

How long does it take the moisture content to stabilize in a wood truss? I live in southern California. Also, how much deflection should be expected in a scissors truss over a partition wall?