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This specification covers the minimum requirements for the installation of cast-in-place reinforced gypsum concrete over permanent formboard. Subpurlins shall be designed to support live and dead loads of the roof deck. Got-rolled and cold-rolled steel shapes other than bulb trees or truss tees shall meet the requirements of this specification. Mineral fiber formborad shall be tested in accordance with the transverse loading test. Hexagonal reinforcing mesh, rectangular reinforcing fabric, gypsum concrete, and expansion filler strip shall be fabricated in accordance to the specification. The subpurlins shall be placed transversely to the purlins and primary framing and shall be spaced to suit the size of the formboards. Cross tees shall be provided where formboard ends are supported by purlins or the primary framing. Formboards shall be located face down on the flanges of the supporting members and with the ends on top of the purlins. The mesh of wire fabric shall be located with the main longitudinal wires at right angles to the subpurlins and adjacent to the formboard at midspan between the purlins. Expansion filler strips shall be placed continuously against the walls, curbs, nailers, or other rigid surfaces that gypsum concrete will abut. Gypsum concrete mixing and placement shall be performed. Mixing shall be thorough but not overmixed.