Drywall

Wallboard, the ubiquitous interior building material.

Drywall (also called Wallboard, gypsum board, GWB, plasterboard, SHEETROCK® and Gyproc®) is an inexpensive building material consisting of gypsum formed into a flat sheet and sandwiched between two pieces of heavy paper. As of 2005, it is the most common material globally for the construction of interior walls and ceilings.

Drywall is made primarily from gypsum rock (hydrous calcium sulphate) and is formed by sandwiching a core of wet gypsum between two sheets of heavy paper. When the core sets and is dried, the sandwich becomes rigid and strong enough for use as a building material. Drywall is fire-resistant because in its natural state, gypsum contains water, and when exposed to heat or flame, this water is released as steam, retarding heat transfer. A special fire-rated (Type X) drywall is formulated by adding noncombustible fibers to the gypsum, helping to maintain integrity at high temperatures.

Drywall is typically available in four-foot wide sheets of various lengths, commonly 8 feet, 10 feet, or 12 feet. In some commercial applications, sheets up to 16 feet are used. Larger sheets make for faster installation, since they reduce the number of joints that must be finished. The most commonly used drywall is 3/8 inch and 5/8 inch thick, but can range from 3/8 inch to 1 inch thick.

Drywall is cut to size by scoring the paper on the front side (usually white), breaking the sheet along the cut, scoring the paper backing, and finally breaking the sheet in the opposite direction. Small features such as holes for outlets and light switches are usually cut using a keyhole saw. Drywall is then fixed to the wall structure with nails, or more commonly in recent years, screws. In some applications, the drywall may be attached to the wall with adhesives.

After the sheets are secured to the wall studs and/or ceiling joists, the seams between drywall sheets are concealed using joint tape and several layers of joint compound. The compound is then typically sanded before painting. Alternatively, for a better finish, the entire wall is given a skim coat (a thin layer of finishing plaster). For this application square-edged boards are used, rather than the tapered edge boards that are used to conceal the tape in taped jointing.

The name drywall derives from drywall's replacement of the lath and plaster wall building method, in which plaster was spread over small wooden formers while still wet. This method was time consuming and labor intensive (although skilled plasterers could do the job with great rapidity), whereas an entire house can be drywalled in a day or two by two experienced "drywallers", and drywall is easy enough to use that it can be installed by many amateur home carpenters. In large-scale commercial construction, the work of installing and finishing drywall is often split between the drywall mechanics, or hangers, who install the wallboard, and the tapers and mudman, or float crew, who finish the joints and cover the nailheads with drywall compound.

Greenboard is water resistant drywall. 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.

Drywall provides an R-Value of 0.32 for 3/8" board, 0.45 for 1/2" board, 0.56 for 5/8" and 0.83 for 1" board. In addition to increased R-Value, thicker drywall has a higher STC.

Common Drywall Tools

• Keyhole saw
• Drywall screws or nails
• Electric screwdriver
• Dimpler
• Taping knives of several sizes, commonly 6", 8", 10", and 12"
• Inside/outside corner trowels

System manufacturers

• British Gypsum (see the industry standard manual the White Book)
• Lafarge
• United States Gypsum (USG)