| Drywall
(also called wallboard, gypsum board, GWB, plasterboard, SHEETROCK®
and Gyproc®) is a building material consisting of gypsum
formed into a flat sheet and sandwiched between two pieces
of heavy paper. As of 2005, it is the most common material
globally for the construction of interior walls and ceilings.
Drywall
is made primarily from gypsum rock (hydrous calcium sulphate)
and is formed by sandwiching a core of wet gypsum between
two sheets of heavy paper. When the core sets and is dried,
the sandwich becomes a strong, rigid building material. Drywall
is fire-resistant because in its natural state, gypsum contains
water, and when exposed to heat or flame, this water is released
as steam, retarding heat transfer. A special fire-rated (Type
X) drywall is formulated by adding noncombustible fibers to
the gypsum, helping to maintain integrity at high temperatures.
Drywall
is typically available in four-foot wide sheets of various
lengths, commonly 8 feet, 10 feet, or 12 feet. In some commercial
applications, sheets up to 16 feet are used. Larger sheets
make for faster installation, since they reduce the number
of joints that must be finished. The most commonly used drywall
is 3/8 inch and 5/8 inch thick, but can range from 1/2 inch
to 1 inch thick.
Drywall
is cut to size by scoring the paper on the front side (usually
white), breaking the sheet along the cut, scoring the paper
backing, and finally breaking the sheet in the opposite direction.
Small features such as holes for outlets and light switches
are usually cut using a keyhole saw. Drywall is then fixed
to the wall structure with nails, or more commonly in recent
years, screws. In some applications, the drywall may be attached
to the wall with adhesives.
After
the sheets are secured to the wall studs and/or ceiling joists,
the seams between drywall sheets are concealed using joint
tape and several layers of joint compound. The compound is
then typically sanded before painting. Alternatively, for
a better finish, the entire wall is given a skim coat (a thin
layer of finishing plaster). For this application square-edged
boards are used, rather than the tapered edge boards that
are used to conceal the tape in taped jointing.
The
name drywall derives from drywall's replacement of the lath
and plaster wall building method, in which plaster was spread
over small wooden formers while still wet. This method was
time consuming and labor intensive (although skilled plasterers
could do the job with great rapidity), whereas an entire house
can be drywalled in a day or two by two experienced "drywallers",
and drywall is easy enough to use that it can be installed
by many amateur home carpenters. In large-scale commercial
construction, the work of installing and finishing drywall
is often split between the drywall mechanics who install the
wallboard, and the mudman or tapers, who finish the joints
and cover the nailheads with drywall compound.
Greenboard
is water resistant drywall. It is suitable for humid areas,
but not areas that actually get wet. Concrete backerboard
(concrete reinforced with fiberglass) should be used where
actual moisture is expected. Concrete backerboard is typically
used as the underlayment for ceramic tile.
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