There are several different schools of thought when it comes to defining the term wallboard. Broadly speaking, wallboard 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 wallboard is often used interchangeably with drywall, sheetrock or paneling. Some builders strictly define wallboard 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, wallboard begin as one continuous sheet. Special cutters separate this gypsum-and-paper sheet into individual sections of wallboard, or drywall.

In the United States, the standard wallboard size is generally four feet wide by eight feet long, although the length can be as much as sixteen feet for larger projects. Elsewhere, the standard wallboard panel is approximately 1,200 mm wide by 2,400 mm long, but the length can be adjusted in 300 mm increments. The average thickness of wallboard 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. The wallboard can be oriented vertically or horizontally, but horizontal placement is a common way to avoid creating too many seams between panels. Vertical wallboard placement works well when the walls are precisely eight feet (2,400 mm) 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 wallboard. 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 wallboard 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 of wallboard: standard, type X and green. Standard wallboard 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 wallboard is engineered for high moisture areas, such as the basement or bathroom.