Building Design and Construction Handbook - Merritt - Ventech!

4.36 SECTION FOUR
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:
1 ⁄4 in—for covering and rehabilitating old walls and ceilings, 4 to 12 ft long
5 ⁄16 in—where thickness greater than 1 ⁄4 in is desired, 4 to 14 ft long.
3 ⁄8 in—mainly for the outer face in two-layer wall systems, 4 to 16 ft long
1 ⁄2 in—for single-layer new construction with supports 16 to 24 in c to c, 4 to
16 ft long
5 ⁄8 in—for better fire resistance and sound control than 1 ⁄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 1 ⁄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, 1 ⁄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
3 ⁄8, 4 ⁄10, 1 ⁄2, and 5 ⁄8 in thick.
Gypsum Formboard. This type is used as a permanent form in the casting of
gypsum-concrete roof decks.
(‘‘Architect Data Book—Construction Products and Systems,’’ Gold Bond Building
Products, a National Gypsum Division, 2001 Rexford Road, Charlotte, NC