This product consists of a core of set gypsum surfaced with specifically manufactured paper firmly bonded to the core. It is designed to be used without addition of plaster for walls, ceilings, or partitions and provides a surface suitable to receive either paint or paper (see also Sec. 11). Gypsumboard is extensively used in drywall construction, where plaster is eliminated. It is also available with one surface covered with aluminum or other heat-reflecting type of foil, or with imitation woodgrain or other patterns on the exposed surface so that no additional decoration is required.
The types of gypsumboard generally available include wallboard, backing board, coreboard, fire-resistant gypsumboard, water-resistant gypsumboard, gypsum sheathing, and gypsum formboard.
Gypsum Wallboard. This type is used for the surface layer on interior walls and ceilings. Regular gypsum wallboard comes with gray liner paper on the back and a special paper covering, usually cream-colored, on facing side and edges. This covering provides a smooth surface suitable for decoration. Foil-backed gypsum wallboard has aluminum foil bonded to the liner paper to serve as a vapor barrier and, when contiguous to an airspace, as thermal insulation. Predecorated gypsum wallboard does not require decorative treatment after installation because it comes with a finished surface, often a decorative vinyl or paper sheet. Wallboard should conform with ASTM C36.
Wallboard usually is available 4 ft wide in the following thicknesses and lengths:
1â„4 in for covering and rehabilitating old walls and ceilings, 4 to 12 ft long
5â„16 in where thickness greater than 1â„4 in is desired, 4 to 14 ft long.
3â„8 in mainly for the outer face in two-layer wall systems, 4 to 16 ft long
1â„2 in for single-layer new construction with supports 16 to 24 in c to c, 4 to 16 ft long
5â„8 in for better fire resistance and sound control than 1â„2 in provides, 4 to 16 ft long
Standard edges are rounded, beveled, tapered, or square.
Backing Board. This type is used as a base layer in multi- ply construction, where several layers of gypsumboard are desired for high fire resistance, sound control, and strength in walls. It has gray liner paper on front and back faces. Also available is backing board with aluminum foil bonded to the back face. Gypsum backing board should conform with ASTM C442. The boards come 16 to 48 in wide, 4 to 16 ft long, and 1â„4 to 1 in thick.
Gypsum Coreboard. To save space, this type is used as a base in multi-ply construction of self-supporting (studless) gypsum walls. Coreboard may be supplied as
1-in-thick, solid backing board or as two factory-laminated, 1â„2-in-thick layers of backing board. Coreboard too should conform with C442.
Type X Gypsumboard. For use in fire-rated assemblies, Type X may be gypsum wallboard, backing board, or coreboard with core made more fire resistant by addition of glass fiber or other reinforcing materials.
Water-Resistant Gypsum Backing Board. This type comes with a water-resistant gypsum core and water-repellant face paper. It may be used as a base for wall tile in baths, showers, and other areas subject to wetting. The board should conform with ASTM C630.
Gypsum Sheathing. This type is used as fire protection and bracing of exterior frame walls. It must be protected from the weather by an exterior facing. Sheathing should conform with ASTM C79. It comes 24 to 48 in wide, 6 to 12 ft long, and 3â„8, 4â„10, 1â„2, and 5â„8 in thick.
Gypsum Formboard. This type is used as a permanent form in the casting of gypsum-concrete roof decks.
