Drywall panels cover most walls and ceilings built over the last 40 years. These panels have a layer of gypsum sandwiched between heavy paper facings. A waterproof type sometimes called green board is used in bathrooms and other areas subject to heavy moisture. The sheets, which are relatively inexpensive, are 4 feet wide, 1/4 to 5/8 inch thick, and 6 to 16 feet long. The standard size is 1/2 inch thick and 8 feet long.

Drywall sheets are applied to studs, joists, or rafters with drywall nails or screws, or with adhesive. Joints between the panels are covered with a paper or fiberglass tape and coated with several layers of smooth, plasterlike joint compound.

Most ceilings are built with the same materials and methods as walls. They consist of wood framing members joists rather than wall studs and normally are clad with drywall or plaster.

A conventional drywall ceiling consists of drywall panels screwed or nailed to ceiling joists. Joints between the panels are taped and finished with drywall compound using the same methods as for walls. These ceilings are normally hung before the drywall is applied to the walls. Older ceilings often have lath-and-plaster construction.

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Drywall styles: There are two basic drywall finish styles: smooth and textured. Textured finishes range from light to medium and heavy, with both simple and complex textures. There are two types of smooth wall finish: smooth for wallpaper and smooth for paint (paint roller leaves a slight stipple finish).

Most people elect to keep their walls unfinished in garages, storage and other work areas. A sprayed drywall texture is the most popular application method today. It uses less labor and isn't as costly as hand-applied finishes.

Fine to coarse grades of texture can be sprayed. The texture is made coarser by adding textured granules (of foam, for instance) to the drywall compound or paint.

Matching drywall: If you are matching existing drywall and having it professionally installed, it's important to let your service professional know the size and texture type so a more accurate estimate can be delivered.

While metal studs make for stronger, straighter frames, wooden studs are America's most popular way to frame. Kiln dried studs have all the moisture removed before they are used so they stay straight. Untreated lumber will warp as it ages.