Backbox

Backbox is a term used primarily in construction and electrical work to describe a hollow enclosure installed in a wall or partition to contain electrical devices and wiring. Its main purpose is to provide a mounting point for outlets, switches, or fixtures, while protecting the conductors and helping to create a clean, flush wall surface.

Backboxes come in various forms and sizes. Common configurations include single-gang boxes for a single device, double-gang boxes for two devices, and larger sizes for multiple controls or outlets. They may be made from metal (often galvanized steel), plastic, or other composite materials. Depth options range from shallow to deep, depending on the number of cables and the thickness of the device to be mounted. There are new-work boxes that are installed before wall material is applied and old-work (retrofit) boxes that secure to finished walls, often with mounting wings or clamps. Plaster rings or extension rings are sometimes used to bring the finished wall surface to the correct level.

Installation considerations include ensuring the box has adequate volume for the cable fill required by the electrical code, proper cable clamps or connectors, and a mechanism to secure devices with a stable mounting surface. Fire-resistance ratings and compatibility with the surrounding wall material may also be factors, particularly in hidden or shared-wall installations.

Beyond electrical use, the term backbox can refer to any enclosure used behind a device to conceal wiring or components, such as housings for audio/visual equipment or appliances. In all cases, a backbox serves to organize and protect wiring while providing a stable mounting point.