Backboxes

Backboxes are enclosures installed in walls, ceilings, or other surfaces to house electrical outlets, switches, or other devices. They provide a mounting point, protect cables, and allow devices to sit flush with the finished surface. In the UK and Ireland the term back box is common; in other regions these may be referred to as electrical boxes or recessed boxes.

Design and variants: The most common types are single-gang, double-gang, or larger, with depths ranging from shallow to deep (roughly 25 mm to 50 mm) to fit cables and devices. Materials include plastic (often PVC or ABS) and metal (galvanized steel or steel with plaster-in). There are recessed boxes installed within a wall cavity and surface-mounted boxes fixed to the surface. For tiling or plasterwork, plaster rings or adjustable backboxes help achieve a flush finish.

Installation and use: Selection depends on the device footprint and wall construction. Backboxes must be securely fixed and sized to provide enough volume for cables and devices; in tiled or plastered walls they should accommodate tile thickness and allow plastering. Fire-rated boxes may be required in walls with fire resistance requirements; wet-area boxes provide protection in bathrooms or kitchens.

Standards and safety: Work should comply with local electrical codes and building regulations. Cables should be routed correctly, boxes should not be overfilled, and devices should not protrude beyond the finishing surface.

Common applications: powering outlets, light switches, dimmers, and modular devices; used in homes, offices, and other buildings. Related concepts include electrical box, plaster-in box, and flush-mounted box.