Drywall

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MOTHER'S HANDOOK

For the Wet-Behind-the-Ears

Hanging sheets of gypsum is a rough job-but someone's got to do it.

YOU MAY KNOW IT BY ANY OF ITSmany names-drywall, gypsum, gypboard, plasterboard, or the familiar brand name, Sheetrock. Whatever the label, it can be heavy, cumbersome, and tedious to work with. Yet over 400 billion square feet of the mineral-based material have been wrestled into place in homes and buildings in our collective lifetime.

Gypsum-the earthbound sulfate of calcium to which plaster of paris owes its existencehas been around forever. But it's been only since the turn of the century that an enterprising soul named Sackett developed a method of layering it between sheets of felt paper to produce a "plaster board" that made the hand-troweled wall a thing of the past.

Plasterboard has come a long way since that time, but one thing hasn't changed: It still looks best when installed or repaired according to Hoyle. And even though you may not know a putty knife from a plaster pan, you can learn how drywalling is supposed to be done, make a small investment in tools, and then have an honest go at it. Actually, gypboard is well suited to those who expect to make mistakes, simply because it's relatively inexpensive.

Even if you didn't know it at the time, you've probably seen an unfinished drywall sheet somewhere. Its face (the side that goes toward the interior of the room) is finished in a cream- or natural-colored paper. The back is usually gray, and the edges are trimmed with folded tape to protect them.

Typically, you'll see '/z"-thick paperfaced panels measuring 4' X 8' or 4' X 12', though they're available in lengths up to 16 ' . In better-quality construction, 5/a" board is

used; conversely, 3/a" panels are suitable for economy or two-layer work and when bending radii, while '/4" drywall is reserved for surfacing existing plaster walls.

But the choices don't stop there. Aside from the standard drywall, there's also a 5/a"thick fire-rated sheet (used on walls common to the garage and house and in commercial work), a water-resistant board with specially treated facings and core (for bathrooms, and as a backing for tile and plastic wallboard), and a foil-backed gypboard that incorporates a vapor retarder.

If you sight down the long edge of a drywall panel, you'll notice that the face is tapered toward the edge (Fig. 1). That's to allow a slight recess to accommodate the tape and reinforcing compound, which makes a smooth, strong joint. You cold still use the older style of square-edged panel, however, if you're planning to cover the surface with wallpaper, since the joints won't show.

There's also a special round-edged tapered board that's used on walls and ceilings that might be exposed to high humidity and temperature swings during construction. Conditions like these often cause ridges and beading in the joints; the design allows for an initial filling of setting plaster, which bonds permanently, without shrinking, in an hour or two. Afterwards, a regular joint compound would be used to finish the job.