This specification covers the requirements for glass mat gypsum substrates designed to be used as exterior substrate or sheathing for weather barriers. The substrates shall consist of a noncombustible water-resistant gypsum core, surfaced with glass mat partially or completely embedded in the core. Materials shall be sampled, tested, and conform accordingly to specified physical property (flexural strength, humidified deflection, nail pull resistance, water resistance, and core, end, and edge hardness) and dimensional (thickness, width, length, end squareness, and edges) requirements.

1.1 This specification covers glass mat gypsum substrate, which is designed to be used as an exterior substrate for a weather barrier.

1.2 The values stated in either inch-pound units or SI (metric) are to be regarded separately as standard. Within the text, the SI units are shown in brackets. The values stated in each system shall be used independently of the other. Values from the two systems shall not be combined.

1.3 The text of this standard references notes and footnotes that provide explanatory material. These notes and footnotes (excluding those in tables and figures) shall not be considered as requirements of the standard.