Drywall Raw materials

Drywall is made primarily from the semi-hydrous form of calcium sulphate (CaSO4.½ H2O) plaster created by heating ground gypsum rock (hydrous calcium sulfate). The plaster is mixed with fibre (typically paper and/or fibreglass), foaming agent, various additives that increase mildew and fire resistance, and water and is then formed by sandwiching a core of wet gypsum between two sheets of heavy paper or fiber glass mats. When the core sets and is dried, the sandwich becomes rigid and strong enough for use as a building material.


Types of Drywall

Regular white board
Fire-resistive ("Type X") comes in various ratings based the time the product can withstand standardized fire test. Often perlite, vermiculite and boric acid are added to improve fire resistance.
Green—for use in washrooms and other areas expected to experience elevated levels of humidity. This product contains an oil-based additive that provides moisture resistance.
Greenboard is water resistant drywall. Early versions had asphalt added which gave it a brown gypsum core. It is suitable for humid areas, but not areas that actually get wet. Concrete backerboard (concrete reinforced with fiberglass) should be used where actual moisture is expected. Concrete backerboard is typically used as the underlayment for ceramic tile. Enviroboard is a board made from recycled agricultural materials.