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A wall box is a type of building material used to safely hold electrical wiring within a wall. Typically, these boxes are recessed into the wall so that the edge of the box sits flush with the face of the plaster or drywall. Finish plates are installed over the face of the box to give it a smooth, finished appearance. Installers typically secure the wall box to wood framing members within the wall cavity to hold it in place. Electrical wall boxes can be used to hold almost any type of cable or wiring, and may also be joined together to hold multiple sets of wiring in close proximity.
The wall box serves a number of functions, both during construction and after. It protects the components within the box from damage as drywall is hung and finished. It also protects installers from electrical shock by shielding the wires or cables. This prevents an installer from accidentally hammering a nail into a live wire, and helps to minimize the risk of electric shock.
Electrical wall boxes also make it easier to organize and locate wires, and also to determine which wires are linked to each wall outlet or other device. By insulating these wires from other structures within the wall, the wall box also lowers the risk of fire. Finally, if the builder plans to install electrical elements that the homeowner may not use immediately, the wall box stores and protects these devices, and also allows the homeowner to locate them more easily in the future.
Different types of boxes are designed for each type of electrical device. For example, power outlets and light switches each require a specific type of box that is designed to hold all the elements required for each of these devices. The boxes are designed as single-gang, double-gang or even more depending on the number of switches or receptacles it can hold. Larger wall boxes hold sound wiring, thermostats, or other electrical devices. These boxes are made from both plastic and metal, and the choice between the two depends both on budget and local building code requirements.
The size of each wall box depends on the number of wires it contains. Building codes typically have very specific requirements as to how much of the box can be filled with wires or cables. Most builders also choose boxes with some extra space to allow for future renovations or additions. The size requirements can vary widely depending on the type of cable used and how much space it takes up.