Also called wallboard, gyproc, or plasterboard, it is used to cover interior walls and ceilings, and sometimes as an underlay for ceramic tiles. Composed of gypsum (calcium sulfate dihydrate) sandwiched between two layers of kraft paper, it has a fire rating of approx. 30 minutes, and offers reasonable soundproofing, especially when installed in two layers.

Hanging drywall can be fairly heavy work, but not overly difficult to master. It ranges from 1/4" to 5/8" in thickness, with 1/2" being the most common in residential work. The sheets are normally 4 feet wide and 8, 10 or 12 feet long, conforming to standard measuring increments, such as framing studs placed at 16 or 24 inch intervals.

Standard drywall sheets have tapered long edges and the shorts ends are squared off. One face is rough, and one face is smooth, for painting and papering. Water resistant drywall also has tapered edges, and is used for kitchens, bathrooms and laundry rooms. Use cement-based backer board under tub surrounds or ceramics, in tub and shower areas. Some drywall comes pre-finished in different textures, colors and patterns, and some are vinyl-coated.

Wallboard (drywall) sheathing has tongue and groove edges, and is used under exterior claddings, including masonry to provide water and wind protection.

Wallboard sheathing and water-resistant drywall will both sag if used on ceilings - use standard drywall on ceilings, and cover with alkyd primer to water-proof the surface.

Drywall must be carefully measured and cut, before fastening to wood or metal studs, preferably with special drywall screws applied with a drywall gun or a drill, fixed with a drywall "dimpler" to properly counter-sink the screws. Use Type W screws for fastening to wood studs, Type G for fastening one sheet to another, and Type S for fastening sheets to metal studs. The joints are finished with joint compound (mud) and tape (paper or fibre mesh). Outside corners are covered with a metal corner (drywall "bead"). A T-square and utility knife are used for cutting, and a drywall knife (a smooth, broad spreader) is used for applying the compound.

To estimate quantities, add up the square footage to be covered, and divide by the number of square feet in a sheet (eg. 32 for a 4X8 sheet). One pound of nails or 1/2 pound of screws will fasten 200 square feet of drywall. Have a friend help you with the heavy sheets, especially when hanging a ceiling!

Drywall is easiest to install and finish if you hang it sideways, although if your ceiling is higher than 8'1" you might be tempted to hang the sheets vertically.

CAUTION

If hanging sheets vertically, you will be screwing very close to the tapered edge, and if the framing is not perfect, your vertical joints might be weak, or not line up at all!