Construction techniques
As an alternative to a week-long plaster application, an entire house can be drywalled in one or two days by two experienced drywallers, and drywall is easy enough to be installed by many amateur home carpenters. In large-scale commercial construction, the work of installing and finishing drywall is often split between drywall mechanics, or hangers, who install the wallboard, and tapers and mudmen, or float crew, who finish the joints and cover the fastener heads with drywall compound.[citation needed] Drywall can be finished anywhere from a level 0 to a level 5, where 0 is not finished in any fashion and 5 is the most pristine. Depending on how significant the finish is to the customer the extra steps in the finish may or may not be necessary, though priming and painting of drywall is recommended in any location where it may be exposed to any wear.
Drywall screws for wood, with parallel-threaded woodscrew shanks and bugle heads
Drywall is cut to size, using a large T-square, by scoring the paper on the finished side (usually white) with a utility knife, breaking the sheet along the cut, and cutting the paper backing. Small features such as holes for outlets and light switches are usually cut using a keyhole saw or a small high-speed bit in a rotary tool. Drywall is then fixed to the structure with nails or drywall screws and often glue. Drywall fasteners, also referred to as drywall clips or stops, are gaining popularity in both residential and commercial construction. Drywall fasteners are used for supporting interior drywall corners and replacing the non-structural wood or metal blocking that traditionally was used to install drywall. Their function saves material and labour cost, to minimize call-backs due to truss uplift, to increase energy efficiency, and to make plumbing and electrical installation simpler.
When driven fully home, drywall screws countersink their heads slightly into the drywall. They use a 'bugle head', a concave taper, rather than the conventional conical countersunk head; this compresses the drywall surface rather than cutting into it and so avoids tearing the paper. Screws for light-gauge steel framing have an acute point and finely spaced threads. If the steel framing is heavier than 20-gauge, self-tapping screws with finely spaced threads must be used. In some applications, the drywall may be attached to the wall with adhesives.
Applying "joint compound" to drywall
After the sheets are secured to the wall studs or ceiling joists, the installer conceals the seams between drywall sheets with "joint tape" and several layers of "joint compound" (sometimes called "mud"), typically spread with a taping knife or putty knife. This compound is also applied to any screw holes or defects. The compound is allowed to air dry then typically sanded smooth before painting. Alternatively, for a better finish, the entire wall may be given a "skim coat", a thin layer (about 1 mm or 1/16 inch) of finishing compound, to minimize the visual differences between the paper and mudded areas after painting.
Another similar skim coating process is called veneer plastering, although it is done slightly thicker (about 2 mm or 1/8 inch). Veneering uses a slightly different specialized setting compound ("finish plaster") that contains gypsum and lime putty. This application uses blueboard, which has special treated paper to accelerate the setting of the gypsum plaster component. This setting has far less shrinkage than the air-dry compounds normally used in drywall, so it only requires one coat. Blueboard also has square edges rather than the tapered-edge drywall boards. The tapered drywall boards are used to countersink the tape in taped jointing, whereas the tape in veneer plastering is buried beneath a level surface. One coat veneer plaster over dry board is an intermediate style step between full multi-coat "wet" plaster and the limited joint-treatment-only given "dry" wall.
Water damage and mold
Drywall water damage in a closet
Drywall is highly vulnerable to moisture due to the inherent properties of the materials that comprise it: gypsum, paper, and organic additives and binders. Gypsum will soften with exposure to moisture, and eventually turn to a gooey paste with prolonged immersion, such as during a flood. During such incidents, some or all of the drywall in an entire building may need to be removed and replaced. Furthermore, the paper facings and organic additives mixed with the gypsum core are food for mold.
The porosity of the board—introduced during manufacturing to reduce the weight of the board, lowering construction time and transportation costs—enables water to rapidly reach the core through capillary action, where mold can grow inside. Water that enters a room from overhead may cause ceiling drywall tape to separate from the ceiling as a result of the grooves immediately behind the tape where the drywall pieces meet becoming saturated. The drywall may also soften around the screws holding the drywall in place and with the aid of gravity, the weight of the water may cause the drywall to sag and eventually collapse, requiring replacement.
Drywall's paper facings are edible to termites, which can eat the paper if they are infesting a wall cavity that is covered with drywall. This causes the painted surface to crumble to the touch, its paper backing material having been eaten. In addition to the necessity of patching the damaged surface and repainting, if enough of the paper has been eaten, the gypsum core can easily crack or crumble without it and the drywall must be removed and replaced.
Drywall damage caused by termites eating the paper, causing the paint to crumble
In many circumstances, especially when the drywall has been exposed to water or moisture for less than 48 hours, professional restoration experts can avoid the cost, inconvenience, and difficulty of removing and replacing the affected drywall. They use rapid drying techniques that eliminate the elements required to support microbial activity while also restoring most or all of the drywall.
It is for these reasons that greenboard and ideally cement board are used for rooms expected to have high humidity, primarily kitchens, bathrooms, and laundry rooms.
Other damage
Foam insulation and the gypsum part of sheetrock are easily chewed out by honeybees when they are setting up a stray nest in a building and they want to enlarge their nest area.