WALLBOARD

any of various large, rigid sheets of finishing material used in drywall construction to face the interior walls of dwellings and other buildings. Drywall construction is the application of walls without the use of mortar or plaster. Wallboard materials include plywood and wood pulp, asbestos-cement board, and gypsum. Wood fibre and pulp boards are made by compressing together layers or particles of wood with adhesives and are manufactured with wood grain and a variety of other surface effects. They are also available with high acoustic (sound-suppressing ) and thermal (insulating) capacities. Asbestos-cement boards are formed from a mixture of portland cement and asbestos fibre that has been wetted and then pressed into a board or sheet form. Organic fibres are added to some asbestos-cement boards to promote resiliency and ease of machining, and boards can also be treated with curing agents, water-repellent admixtures, and a variety of other substances to improve their performance and the ease with which they can be worked. Thin asbestos-cement sheets are usually backed with plywood or insulating board to increase their resistance to impact. One of the most common wallboard types is the gypsum panel. Gypsum, a natural mineral in crystalline form, is a hydrous sulfate of calcium. Gypsum board contains a gypsum rock core sandwiched between two layers of special paper. In fire-resistant panels, required for many types of construction, glass fibres are mixed with the gypsum base. Panels manufactured with an aluminum backing are used for insulation. Gypsum wallboard is manufactured both unfinished and finished with a variety of vinyl and other finishes in permanent colours and textures that require no additional treatment to complete the appearance of interior wall surfaces. Gypsum boards, wood sheets, and wood pulp boards are also used as a sheathing material to cover the exterior of a building's wood superstructure.