This specification covers gypsum boards which include the following: gypsum wallboard for use on walls, ceilings, or partitions and that affords a surface suitable to receive decoration; predecorated gypsum board for use as the finished surfacing for walls, ceilings, or partitions; gypsum backing board, coreboard, and shaftliner board for use as a base in multilayer systems or as a gypsum stud or core in semisolid or solid gypsum board partitions, or in shaft wall assemblies; water-resistant gypsum backing board to be used as a base for the application of ceramic or plastic tile on walls or ceilings; exterior gypsum soffit board for exterior soffits and carport ceilings that are completely protected from contact with liquid water; gypsum sheathing board for use as sheathing on buildings; gypsum base for veneer plaster; gypsum lath for use as a base for gypsum plaster application; and gypsum ceiling board for interior ceilings and walls. Gypsum board shall consist of a noncombustible core, essentially gypsum, surfaced with paper bonded to the core. The specimens shall comply with the following required physical properties: core, end, and edge hardness; straightness of the edges and ends; length; tapered edge depth; flexural strength; humidified deflection; nail pull resistance; permeance; water resistance; and surface water absorption.

1.1 This specification covers the gypsum boards described in 1.1.1-1.1.9.

Note 1—Specifications C840, C841, C844 and C1280 contain application procedures for gypsum board.

1.1.1 Gypsum wallboard, designed for use on walls, ceilings, or partitions and that affords a surface suitable to receive decoration.

1.1.2 Predecorated gypsum board, designed for use as the finished surfacing for walls, ceilings, or partitions.

1.1.3 Gypsum backing board, coreboard, and shaftliner board, designed for use as a base in multilayer systems or as a gypsum stud or core in semisolid or solid gypsum board partitions, or in shaft wall assemblies.

Note 2—The terms backing board, coreboard, and shaftliner board refer to different end uses. The term gypsum backing board, as used in this specification, shall include gypsum coreboard and gypsum shaftliner board unless otherwise stated.

1.1.4 Water-resistant gypsum backing board, designed primarily to be used as a base for the application of ceramic or plastic tile on walls or ceilings. This product is also suitable for decoration.

1.1.5 Exterior gypsum soffit board, designed for use on exterior soffits and carport ceilings that are completely protected from contact with liquid water.

1.1.6 Gypsum sheathing board, designed for use as sheathing on buildings.

1.1.7 Gypsum base for veneer plaster, designed for use as a base for the application of gypsum veneer plaster.

1.1.8 Gypsum lath, designed for use as a base for the application of gypsum plaster.

1.1.9 Gypsum ceiling board, designed for use on interior ceilings with framing spaced not more than 24 in. [610 mm] on center and that affords a surface suitable to receive water-based texture and other decoration. This product is also suitable for use on interior walls.

1.2 Specifications applicable to all gypsum boards are located in Section 1-4 and 13-15. Specifications applicable to specific gypsum boards are located in the following sections:

1.3 The values stated in either SI units or inch-pound units are to be regarded separately as standard. Within the text, the SI units are shown in brackets. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard