To avoid construction delays due to the necessity of mixing plaster ingredients with water on the building site and, after application, waiting for the plaster to cure, drytype construction with gypsum products may be used. (For discussion of other drytype interior finishes, see Arts. 11.30 to 11.31.) For the purpose, gypsumboard is factory fabricated and delivered to the site ready for application.
Gypsumboard is the generic name for a variety of panels, each consisting of a non-combustible core, made primarily of gypsum, and a bonded tough paper surfacing over the face, back, and long edges. Different types of paper are used for specific purposes. Gypsumboard with a factory-applied, decorative face or with an aluminum-foil back for insulation purposes also is available.
The panels may be attached directly to framing, such as studs or joists. While gypsumboard also may be attached directly to unit masonry or concrete, use of furring strips between the panels and backing is desirable because of the possibilities of interference from surface irregularities in the backing or of moisture penetration through exterior walls. Successive panels are applied with edges or ends abutting each other. Depending on esthetic requirements, the joints may be left exposed, covered with battens, or treated to present an unseamed, or monolithic, appearance. Gypsumboard also can be used to construct self-supporting partitions spanning between floor and ceiling.
See also Art. 4.26.
General Application Procedures for Gypsumboard Gypsumboards may be used in single-ply construction (Fig. 11.23) or combined in multiply systems (Fig. 11.27). The latter are preferred for greater sound control and fire resistance. Application and finishing should conform with ASTM C840.
Precautions. When outdoor temperatures are less than 55F, the temperature of the building interior should be maintained at a minimum of 55F for at least 24 hr before installation of gypsumboards. Heating should be continued until a permanent heating system is in operation, or outdoor temperatures stay continuously above 55F. In warm or cold weather, gypsumboards should be protected from the weather.
Green lumber should not be used for framing or furring gypsumboard systems.
Moisture content of the lumber should not exceed 19%, to avoid defects caused by shrinkage as the wood dries. For the same reason, dry lumber should be kept dry during storage and erection and afterward.