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DO IT YOURSELF : Drywall Project? Skill With Knives Is the Key

November 03, 1990|From Popular Mechanics

Drywall--also called wallboard, gypsum board or plasterboard--is probably the most versatile and forgiving wall surface available today.

Less expensive and easier to apply than plaster, it can be frustrating to work with in the finishing stages, as it requires some skill with at least three sizes of compound knives--3, 6 and 10 inches.

Individual drywall panels, called boards, come in a common width of 4 feet, in lengths from 8 to 16 feet in 2-foot increments. Thickness starts at 1/4 inch and progresses by 1/8-inch increments to 3/4 inch. The most common size, by far, is 4 by 8 feet by 1/2 inch.

Each board consists of a gypsum core covered with heavy paper on both sides. The ends are cut square exposing the core. The long edges have a tapered depression about 1 1/2 inches wide for the paper and joint compound that makes a seamless surface between panels.

Start your installation with the ceiling, and install any electrical boxes or fixtures first. Cut matching holes before applying panel cement to the bottom of the joists with a caulking gun and raising the board. Adhesive makes a stronger bond and reduces the number of nails required.

Make it easier to hold ceiling boards in place by tack-nailing a 40-inch-long 2-by-4 to the wall about an inch below the ceiling.

Support one end of the ceiling panel on this cleat while you raise the other end and nail it in place. Then move the cleat for the next panel. Use 1 5/8-inch-long drywall nails 8 inches apart around the perimeter and across the face of the board into every joist that's covered. Dimple, or slightly recess, the nail heads into the paper for future filling.

The same methods cover the walls.

Place panels horizontally so you won't have to apply joint tape while climbing a ladder. Remember to minimize butt joints with their taping bulges. Push the upper wallboards tight against the underside of the ceiling boards. This drastically reduces future cracking. If the ceilings are eight feet or lower, a second board around the perimeter of the room does the job, but higher ceilings in older homes take a third, partial board.

Finish in four steps: apply joint compound, embed paper tape in it directly over the joint line, cover the tape with more compound and let it dry before skimming the joint with a final very thin layer of compound. There are probably as many ways of doing this as there are professional drywall installers, but for beginners, the three-knife method works well.

Start compounding a tapered joint with the six-inch knife. Hold the knife at a 30- to 45-degree angle to the joint, pressing the compound into the depression. Then wipe off the excess.

Tear off a length of tape to cover the entire joint. Press it in place with your fingertips and then lightly smooth it in place with the three-inch knife. If you see a bubble under the tape when you finish there is too little compound in the joint. Fixing this is impossible. Remove the tape and start over.

Once the tape is embedded, cover it with another layer of compound with the six-inch knife. Smooth the joint with the 10-incher. Let the joint dry for a day and then sand with 120-grit paper.

Finish up by lightly sanding the whole job and applying a very thin skim coat of compound to each joint. Wait a day for it to dry, sand the whole job with 180-grit paper and touch up imperfections before priming and painting.

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