There are several different schools of thought when it comes to defining the term wallboard. Broadly speaking, it refers to any acceptable material — wood, plastic or gypsum, for example — used to form finished walls in a building. Plywood or strandboard sheets could be described as wallboard, along with gypsum-based drywall or formed plastic panels. The term is often used interchangeably with drywall, Sheetrock® or paneling. Some builders strictly define it as the gypsum-based drywall sheets most commonly used in home construction.
It is this second definition that appears to be most common. Wallboard is a synonym for plasterboard or drywall, a product created by sandwiching a layer of gypsum between two paper layers. In the factory, it begin as one continuous sheet. Special cutters separate this gypsum-and-paper sheet into individual sections of drywall.
The standard wallboard size is generally 4 feet (1.2 m) wide by 8 feet (2.4 m) long, although the length can be as much as 16 feet (4.9 m) for larger projects. The length can be adjusted in 12 inch (300 mm) increments. The average thickness is around 1/2 inch (12 mm), but it can be up to twice as thick.
Standard wallboard is ideal for forming finished walls in a typical wood stud construction project. The individual panels are placed against the unfinished wall and screwed into the vertical wooden planks, commonly called studs. They can be oriented vertically or horizontally, but horizontal placement is a common way to avoid creating too many seams between panels. Vertical placement works well when the walls are precisely 8 feet (2.4 m) tall.
The seam between the ceiling and the wallboard can be covered with a special drywall tape. All of the other seams between panels can also be covered with tape and a form of wet plaster engineered for this purpose. Once this layer of drywall plaster has dried, it can be sanded down and painted over.
Wallboard has a number of advantages as a building material. Gypsum is cheap to produce and naturally fire-resistant. Repairs to damaged or broken panels can usually be made by trained homeowners in a few hours. The finished wallboard holds interior and exterior paint well, and can even be plastered over for decorative effect.
Be sure to purchase the proper form of wallboard before starting a project. There are three main forms : standard, type X and green. Standard is suitable for general wall construction. Type X is designed to be more fire-resistant, which could be useful in kitchens or living rooms with a fireplace. Green is engineered for high moisture areas, such as the basement or bathroom.