One Hour Roof Ceiling Assembly
Question:
I am looking for a 1-hour roof/ceiling assembly for wood truss construction. I would like to apply the drywall directly to the bottom of the truss and also have insulation for sound control. Is this possible without using channels and what UL number would I use?
Answer:
UL does not appear to list an assembly as described. In fact, there is no tested assembly that matches in all regards. For details about rated truss assemblies, see SBCA Research Report 1509-01: Fire Resistance Rated Truss Assemblies. In addition, SBCA’s Metal Plate Connected Wood Truss Handbook is a comprehensive reference book that contains information about the truss manufacturing industry, including history, design, fabrication, testing, quality assurance and connection details. The handbook includes the following about fire resistance assemblies (see section 17a and section 17b): “Since the insulation will retard the transfer of heat, any insulation incorporated into a rated assembly should be kept as far away from the gypsum surface as possible. Since the plenum cavity helps to dissipate the heat as it passes through the gypsum membrane, maintaining a plenum space that is greater than or equal to that of the tested assembly is critical to the field assembly's performance in a fire.”