Top 5 Gang Boxes Compared for 2026 - Depths, Volumes and BS 4662 Fitment for UK Installations
A gang box houses two or more switches or sockets behind one faceplate. In the UK the part is normally called a back box: flush metal and dry-lining boxes are made to BS 4662 in 16, 25, 35 and 47 mm depths, and a UK accessory screws to 60.3 mm fixing centres on a single gang, 120.6 mm across a double. Installation itself is governed by BS 7671, the IET Wiring Regulations. One thing to be clear about before you read the list below: all five boxes here are North American parts, built to NEC dimensions and typically 3-1/2 in (89 mm) deep with imperial device centres. They will not accept a BS 1363 socket or a UK switch plate. Use them as a reference, or for work on a North American installation; for a UK job, buy a BS 4662 back box in the right depth (Appleby, MK, Schneider, Deta and BG all make them).
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Top Picks Summary
Thomas & Betts Steel City 2-Gang Adjustable Depth Device Box
This Steel City 2-gang adjustable depth device box earns a best-in-class position for gang boxes thanks to its heavy-gauge steel construction and robust adjustable-depth feature that simplifies flush mounting in commercial and retrofit jobs. Compared with the lighter PVC options on this list (like IBERVILLE and Carlon) it offers superior grounding, fire resistance and long-term durability, which justifies a modestly higher upfront price for projects where longevity and code compliance matter.
Estimated£3 – £8
IBERVILLE 3-Gang PVC Electrical Box
The IBERVILLE 3-gang PVC electrical box stands out as the cost-conscious choice for gang box needs, offering corrosion-resistant, nonconductive PVC at a lower price point ideal for residential and damp-location installations. While it lacks the depth adjustability and metal grounding benefits of the Steel City, Carlon and steel boxes, its affordability and ease of installation make it the practical market leader for basic, budget-focused applications.
Estimated£2 – £6
Carlon B234ADJ 2-Gang Adjustable Wall Box
Carlon's B234ADJ 2-gang adjustable wall box combines the economic advantages of PVC with the flexibility of an adjustable depth feature, making it a top pick for retrofit and new-construction residential gang box installs. It strikes a middle ground between the inexpensive fixed PVC IBERVILLE box and heavier steel boxes like Arlington and Thomas & Betts, delivering lower material cost than steel while avoiding some of the fitment compromises of nonadjustable plastic boxes.
Estimated£3 – £8
Arlington Industries F102 2-Gang Steel Box
Arlington's F102 is the non-metallic pick in this group: a one-piece 2-gang One Box, 3-1/2 in (89 mm) deep with 42 cu in of volume, screw-mounted for new or old work. It is frequently mistaken for a steel box. It is not one, and it carries no metallic grounding path, so the circuit protective conductor has to land on the accessory itself. Against the steel Steel City and RACO boxes it trades mechanical protection for lower cost and faster fitting.
Estimated£3 – £10
What UK Standards Say About Back Boxes
Two documents set UK practice, and neither is a North American code. BS 4662 defines the dimensions and test requirements for flush boxes used with switches and sockets - depth, knockouts, earth terminal, and the adjustable lug that lets you square a faceplate up. BS 7671 (IET Wiring Regulations, 18th Edition) governs the installation: earthing, space for conductors, and enclosure suitability for the location. Depth is the most common thing people get wrong. A 25 mm box is fine behind a plain switch but too shallow for many dimmers and smart modules, which is exactly why 35 mm and 47 mm boxes exist.
Standards: BS 4662 covers the box itself; BS 7671 (IET Wiring Regulations, 18th Edition) covers how it is installed and earthed. NEC or CSA markings on an imported box carry no weight for a UK inspection.
Depth drives compatibility: 25 mm suits plain switches and standard sockets; dimmers, USB sockets and smart modules usually need 35 mm, and 47 mm gives room for thick cable or several T&E entries.
Fixing centres are fixed: UK plates screw to 60.3 mm centres on a single gang and 120.6 mm on a double, so box and accessory must both be BS 4662. A North American device box will not line up.
Metal or moulded: galvanised steel boxes accept an earth terminal and give mechanical protection in solid walls; dry-lining boxes clip into plasterboard, and with a plastic box the circuit protective conductor lands on the accessory instead.
Wet and outdoor locations: BS 7671 requires an enclosure with an IP rating suited to the location. A standard indoor back box is not weatherproof - use a purpose-made IP-rated box for external sockets.
Frequently Asked Questions
Will a US or Canadian gang box fit a UK socket?
No. UK switches and sockets screw to 60.3 mm fixing centres on a single gang and 120.6 mm on a double, on a BS 4662 box. North American device boxes use imperial device centres and are typically 3-1/2 in (89 mm) deep, so the screws do not line up and the plate will not cover the aperture. Every box listed on this page is a North American part.
What depth back box do I need?
25 mm is enough for a plain switch or a standard socket. Dimmers, USB sockets, smart switches and anything with a module behind the plate generally need 35 mm, and 47 mm gives room for thick cable or multiple T&E entries. BS 4662 boxes are made in 16, 25, 35 and 47 mm depths.
Which gang box should I buy for retrofits?
Of the boxes listed here, the Thomas & Betts Steel City 2-Gang Adjustable Depth Device Box - its sliding depth lets you sit the front edge flush across varying wall finishes. For a UK retrofit into plasterboard, use a BS 4662 dry-lining box instead, and go to 35 mm if the accessory is a dimmer or a smart module.
Does the Carlon B234ADJ support flush mounting?
Yes. The B234ADJ is a 2-gang, 34 cu in PVC new-work box on an adjustable bracket, so the box face can be set flush with the finished surface. It is a North American box and will not take a UK faceplate.
Conclusion
The five boxes above - Thomas & Betts Steel City 2-gang adjustable-depth box, IBERVILLE 3-gang PVC box, Carlon B234ADJ 2-gang adjustable wall box, Arlington F102 2-gang non-metallic box, and the Hubbell RACO 697 3-gang masonry box - are all North American parts. Of them, the Steel City box is the most adaptable and the RACO 697 the most robust, but none of them will take a BS 1363 socket or a UK switch plate. For UK work, match the accessory to a BS 4662 back box in the right depth (25 mm for a plain switch, 35 mm or 47 mm for dimmers, USB sockets and smart modules) and follow BS 7671 for earthing. Use the site search to compare depths and mounting styles.