One-hour fire-rated wall boards include Sheetrock Brand Ultralight FirecodeX Gypsum panels, Durock Brand Cement Board Next Gen, and Sheetrock Brand Firecode Core - Type X. Wall board assemblies consist of wood, steel or concrete block framing, insulation and gypsum wall board. These materials, combined with wood or steel studs, appropriately-sized air cavities, and sheathings, batts, blankets and bracings meet various fire test standards qualifying them for a one-hour fire-rating.
A typical one-hour fire-rated wall assembly, approved by Universal Laboratories, consists of 2 x 4 inch wood wall studs and R-13 glass fiber insulation, faced with a vapor-retarding foil, filling the cavities. A 5/8-inch thick, Type X gypsum wallboard hangs vertically, to reduce the number of joints and possible fire entry points, inside the studs. Type X gypsum wallboard, with a core that is 21 percent water, includes additives that release steam under high heat, which reduces the spread and heat of a fire. A sheathing then covers the wallboard; another layer of Type X wallboard covers the sheathing; and finally, an air/vapor barrier completes the assembly, which is then ready for cladding. Framing with metal studs or concrete blocks instead of wood studs, and increasing the thickness of the sheathing, eliminates the need for the second layer of wallboard in this assembly.
Type X 5/8-inch gypsum wallboard must meet the international standards of the American Society for Testing and Materials, but the wallboard is not tested by itself. Testing standards mandate the inclusion of all the wall assembly components to establish the fire rating.