DRYWALL CONSTRUCTION

a type of construction in which the interior wall is applied in a dry condition without the use of mortar. It contrasts with the use of plaster, which dries after application. The materials used in drywall construction are gypsum board, plywood, fibre-and-pulp boards, and asbestos-cement boards. The large, rigid sheets are fastened directly to the frame of the building with nails, screws, or adhesives or are mounted on furring (strips of wood nailed over the studs, joists, rafters, or masonry, which allow free circulation of air behind the interior wall). Specialized tools for hanging drywall include the drywall hammer and the joint tool, which is similar to a plastering trowel but made of flexible steel with a concave bow. It is used to apply and smooth a plasterlike compound in joints between wallboards, feathering it out so that the outer edges virtually disappear and the joint, when painted, effectively becomes invisible. Nailheads, slightly depressed or dimpled by the hammer, disappear when similarly treated. Drywall construction is used to avoid delays, because the interior walls do not have to dry before other work can be started, and to obtain specific finishes. Wallboard is manufactured in both finished and unfinished forms. Finished wallboards are faced with vinyl or other materials in a variety of permanent colours and textures, so that they need not be painted when installed. Backing materials and composition of the panel base determine the degree of insulation, fire resistance, and vapour barrier afforded. Wallboards are fire-rated from 1 hour to 4 hours according to the time that a fire's progress would be retarded by the wallboard. Because drywall is mounted on the frame of a building, the framing lumber must be straight for the interior wall to align perfectly; and the lumber must have low moisture content to avoid loosening of the drywall nails. These problems are not encountered in the use of plaster for interior finishes. However, because of the time that it saves, drywall construction has become relatively common in residential buildings.