ASTM International Standard Specification for Application of Gypsum Sheathing ASTM C1280-09

This specification covers the minimum requirements for and the methods of application of gypsum sheathing for use as a substrate for exterior wall cladding. Gypsum sheathing board is a substrate that shall be covered by an exterior cladding or other weather-resistive barrier and is not intended for long-term exposure. Framing members shall be installed so that the surface will be in an even plane, unless otherwise specified, after the gypsum sheathing has been applied. The gypsum sheathing shall be cut by scoring and breaking or by sawing, working from the face side. The cut edges and ends of gypsum sheathing shall be trimmed to obtain neat fitting joints when installed. Gypsum sheathing shall be fitted snugly around all window and door openings. Control joints, other accessories, and metal plaster base shall be fastened through gypsum sheathing to framing members. Where fire resistance or shear resistance is not required, and when metal lath and Portland cement plaster are to be applied as the exterior cladding over gypsum sheathing installed over framing members and the metal lath shall be installed after the gypsum sheathing, the gypsum sheathing shall be permitted to be applied and fastening of the gypsum sheathing shall be completed with the attachment of the self-furred metal lath.