ASTM C1280-18 PDF Download

The ASTM C1280-18 standard sets forth the minimum requirements and methods for the application of gypsum sheathing as a substrate for exterior wall cladding. The gypsum sheathing is intended to be covered by an exterior cladding or weather-resistive barrier and is not designed for long-term exposure.

The standard specifies that framing members must be installed in such a way that the surface is even after the gypsum sheathing is applied, unless otherwise specified. The gypsum sheathing can be cut either by scoring and breaking or by sawing from the face side, with the cut edges and ends trimmed to achieve neat fitting joints during installation. It is also required that the gypsum sheathing be fitted snugly around all window and door openings.

Additionally, the standard outlines the use of control joints, other accessories, and metal plaster base that shall be fastened through the gypsum sheathing to the framing members. In cases where fire resistance or shear resistance is not required, and when metal lath and Portland cement plaster are applied as the exterior cladding, the gypsum sheathing can be applied first, with fastening completed through the attachment of self-furred metal lath.

The standard includes specifications for the application of exterior gypsum panel products specifically designed for use as a substrate for exterior cladding, excluding products designed for interior applications. It also acknowledges that specific construction details for achieving required fire resistance, sound control, or resistance to racking loads or shear should be obtained from reports of fire-resistance tests, acoustical test reports, or racking/shear test reports, respectively.

Furthermore, the standard notes that some sections reference additional explanatory material but clarifies that these notes should not be considered as requirements of the standard.