25mm generally suits standard light switches, 35mm helps with flat‑plate fronts or extra terminations, and 47mm gives more space for USB sockets, smart modules or heavier cabling. Always allow room for gentle cable bends and connectors.
Back Boxes, Pattress & Dry Lining Options Explained
Socket and switch boxes provide a safe, secure housing for wiring and fittings behind faceplates. This range covers flush metal back boxes for masonry, dry lining boxes for plasterboard, and surface pattress boxes where chasing isn’t practical, along with accessories such as joint boxes and terminal strips. Typical depths include 25mm, 35mm and 47mm to accommodate standard switches, deeper socket modules and multi‑cable terminations, with metal boxes generally supplied with an earth terminal and 20mm knockouts for conduit or glands. Use these boxes for new points, refits and upgrades, pairing with Switches and routing with Trunking & Conduit to keep runs protected and tidy.
In practice, metal flush boxes suit brick or block walls, offering rigid support and earthing continuity for faceplates to BS 4662, the UK standard that sets box dimensions and test requirements. Dry lining boxes clamp to plasterboard without studs, making cut‑outs fast and clean, while pattress boxes allow surface mounting where wall depth or services prevent recessing. When selecting depth, allow space for cable bends, connectors and any extra‑deep accessories such as USB sockets or flat‑plate fronts, which often benefit from 35mm or 47mm boxes. For wiring, combine with Electrical Cable, then use grommets or glands in knockouts to protect sheaths and maintain tidy cable entry.
When installing choose 60.3mm fixing centres for single‑gang plates and 120.6mm for doubles, check knockouts, and position boxes flush with the finished surface for a neat fit. On plasterboard, mark and cut carefully, then tighten the lugs evenly on a 1 Gang Dry Lining Box; for retrofits on solid walls, set a metal box level, fix securely and earth it using the provided terminal before fitting your accessory. Surface wiring to sheds, garages or utility areas can be finished quickly with a 2 Gang Pattress Box 47mm and mini trunking, while quick joins inside enclosures are simplified with a 5 Amp Strip Connector. If the location is damp or exposed, select appropriately IP‑rated enclosures and accessories, following BS EN 60529 guidance on ingress protection.
Socket & Switch Boxes FAQ's
Metal boxes are supplied with an earth terminal and, while many installations achieve earth continuity through the fixed lug and faceplate screws, best practice is to fit a short earth link to the box’s terminal when practical.
Boxes must be paired with accessories and enclosures that match the environment. In wet or exposed areas, check IP ratings under BS EN 60529, and follow the placement rules in BS 7671 for zones, RCD protection and suitable equipment.
Single‑gang accessories use 60.3mm fixing centres, doubles use 120.6mm. This ensures compatibility with UK back boxes specified to BS 4662.
Use a dry lining box on plasterboard where there’s no stud or you want to avoid chasing. The spring or clamp lugs grip the board, giving a secure mount for the accessory; use a metal flush box when recessing into masonry.