Substituting Fire Rated Wood Truss Assemblies For Light Gauge Steel
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. Can you furnish me with any laboratory tested (and fully documented) fire-rated wood truss assemblies, which can meet the requirements as indicated above?
Section 17a and section 17b of SBCA’s Metal Plate Connected Wood Truss Handbook describe a variety of one-hour rated wood assemblies. For additional information on fire-resistance-rated assemblies, see SBCA Research Report 1509-01: Fire Resistance Rated Truss Assemblies.
Keep in mind that many fire-rated wood truss assemblies call for a minimum depth of 12 in. Therefore, in most cases, you will need a high heel, whereas in UL P523 you do not. With this in mind, UL P522, P533, P538, P545, P547, P552, P554, P556 and P559 are all suitable wood truss substitutes for UL P523.