What is drywall?

For many years lath and plaster was used to form interior walls. Benjamin Franklin first introduced gypsum plaster to the United States after discovering its use in France. It wasn’t long before plaster was being applied to wood lath on walls.

Lath and plaster is a wet application system. Wet plaster was typically spread over wood strips and toweled to the desired finish. Gypsum board, a core of gypsum with paper facing on each side, is generally a dry material by comparison. Gypsum wallboard was considered to be a “dry wall” compared to plaster, hence the name.

Drywall can also be called gypsum board, plasterboard, and wallboard. The term “sheetrock” is actually a brand name for gypsum board products produced by the United States Gypsum Company (USG).

USG made the first gypsum board panel (drywall). It was 48 inches by 96 inches.

Calcined gypsum is mixed with water and additives to make slurry that is poured between two continuous layers of paper. The slurry hardens as it moves along the conveyor, bonding to the paper, forming a stiffened board that is cut to length.

Gypsum is a naturally occurring mineral known as calcium sulfate dehydrate. The mineral is mined, crushed, ground to fine powder, and dried. The drying process removes three-quarters of the water in the gypsum in a process called calcining. The calcined gypsum can be used to make plaster, gypsum board, and many other gypsum products.

Drywall is used extensively in the United States as a wall board applied over framing. The product is inexpensive and is very versatile in forming wall and ceiling systems. The panels are fastened to the framing and the joints and fasteners are covered with tape and joint compound.

The biggest advantage of using gypsum as a wall material is that it releases steam when subject to fire conditions. The steam suppresses fire making it possible to use gypsum panels as fire protective surfaces in constructing a building. Tested and approved walls can be built with up to four hour fire protection.