Repairing Drywall

If your home was built after 1940, chances are the walls and ceilings are made of wallboard, also called plasterboard or drywall. These are rigid, factory-made sandwich panels (usually 4 feet wide) nailed to interior studs. Seams, nails, and dents from hammering the panels in place all conspire to confound a painter.

Repairing existing drywall is usually not difficult. The most common problems are popped nailheads (nails that come loose and appear as bumps) and peeling joint tape. Gently tap the nails back into place, and cover the dents with a thin layer of a plasterlike mixture called joint compound, which you sand and repaint. To fix peeling tape, cut away the loose piece with a sharp knife and wipe off any flakes of old adhesive. Cover the open seam with fiberglass mesh tape cut exactly to fit. Cover the tape with a smooth layer of joint compound (use a 5-inch flexible joint knife for this), and sand lightly after it dries. Repeat, using larger knives (an 8-inch and then 10-inch knife) so the repair's edges blend with the surrounding surface. Finally, smooth with a damp sponge and repaint.

Fixing a drywall hole (usually caused by a doorknob, sometimes by deranged sports fans) is trickier. Draw a rectangle around the damage, drill 1/2-inch starter holes at each corner, and cut away the rectangle with a keyhole saw. Place two 1x4 strips of wood just behind the wall surface so they frame the hole, leaving at least an inch of wood showing around the hole's sides. Use drywall screws to attach the strips at each corner, screwing through the surrounding drywall just outside the hole edges.

To fill the neat rectangular hole, cut a drywall insert about 1/8 inch smaller than the hole, fit it in place, and secure it to the side-mounted wood strips with drywall screws (countersink them just below the wall surface). Cover the seams and screw holes with self-adhering fiberglass mesh, and cover that with joint compound using a 4-inch joint knife. Using progressively wider joint knives, apply three to four coats of compound, smoothing and feathering the edges. Prime before painting.

If your room contains new drywall, it should be smooth before you prime and paint it. Check that seams and nails have been covered with joint tape and compound, and that there are no rough spots. If the wall is smooth, there will be no telltale show-through after painting.