Fire Rating For Truss Assemblies Built With 2x3 Lumber
Are there any published studies or guidelines on the fire rating of floor trusses built with 2x3 lumber?
Jager Industries of Canada has tested some 45-minute and one-hour rated assemblies for trusses with 2x3 material using Jager/Truswal connector plates. Alpine Engineered Products’ assemblies also include the use of 2x3 members. Contact SBCA if you would like a copy of these assemblies. See Intertek Directory of Certified Products: TSC/FCA 60-02, MCI/FCA 60-02, TSC/FCA 60-06, TSC/FCA 60-10, TSC/FCA 60-08, or TSC/FCA 60-04.
One assembly option that will provide a one-hour rating is a directly applied ceiling of two layers of 5/8-in. type X gypsum board (Gypsum Association “Fire Resistance Design Manual” FC 5406). The assembly is drawn using 2x10 joists. However, the note at the bottom of the assembly description indicates that the two-layer gypsum wallboard ceiling will provide one-hour protection, and therefore wood trusses can be used in place of the wood joists.
For additional information on fire-resistance-rated assemblies, see SBCA Research Report 1509-01: Fire Resistance Rated Truss Assemblies.