Professional Guide

Best Deep Back Boxes for Smart Lighting: 2025 Expert Review

Oli

Fully Qualified 18th Edition Electrician

Published 17 December 2025

If you have ever tried to squeeze a smart lighting module or a bulky WiFi dimmer into a standard UK back box, you know the struggle. Standard 25mm boxes just don't cut it anymore. You end up crushing cables, which isn't just frustrating—it's potentially dangerous.

In Leeds, we have a mix of solid brick back-to-backs (where chasing deep holes is hard work) and stud-wall partitions in newer builds. Choosing the right back box is critical for thermal dissipation and wire management, especially with smart devices that generate a bit of heat.

In this review, I'm looking at three options that help solve the space issue: deep dry-lining boxes for hollow walls and a robust surface-mount solution for those solid walls where chipping out brick isn't an option.

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Specs vs. The Real World

The Spec: "25mm vs 35mm vs 47mm"

The Theory

"Standard light switches fit in 16mm or 25mm boxes."

The Reality

Smart modules (like Shelly or Sonoff) and dimmer packs typically require minimum 35mm, ideally 47mm, to accommodate the neutral wires and connectors without overheating.

The Spec: "Dry Lining Lugs"

The Theory

"They grip any plasterboard automatically."

The Reality

Cheap lugs often snap or strip the thread if you over-tighten them. You need boxes with robust, spring-loaded yellow lugs that don't fail under torque.

My Top 3 Recommendations

Three options to cover different needs and budgets

Evoges 1 Gang Dry Lining Back Box 47mm | Deep Electrical Wall Box

Budget Pick

EVOGES

This 47mm box is the gold standard for installing smart relays behind switches in stud walls. The extra depth provides ample room for Wago connectors and the module itself.

Price£4.99 (at the time of writing)

BrandEVOGES

Depth47mm (Essential for smart modules)

MaterialFlame-retardant plastic

The Good

Generic 47mm depth is perfect for smart home relays
Fast-fix lugs save time on installation
Flame-retardant material adds a layer of safety

The Bad

Only suitable for hollow/stud walls (not solid brick)
Requires cutting a larger hole if retrofitting from a metal box

Installer Tip:

When cutting the plasterboard, ensure you don't cut the hole too wide. The flange on these boxes is minimal. Measure twice, cut once, and verify the cables have enough slack to reach the deeper position.

Priced at £4.99 at the time of writing

Check Price on Amazon

4 Pcs Double Socket Back Box, 2 Gang Surface Mount Pattress Back Box 25 mm Deep

Quality Option

SNSYGN

In many Leeds terraced houses, chasing 47mm into a single-skin brick wall isn't possible or safe. These surface mount boxes are the quality alternative for adding smart sockets without structural damage.

Price£10.99 (at the time of writing)

BrandSNSYGN

TypeSurface Mount (Pattress)

Depth25mm

The Good

Ideal for solid walls where chasing isn't feasible
Clean white finish matches most electrical accessories
Includes knockouts for mini trunking (25x16mm)

The Bad

At 25mm deep, you cannot fit a smart relay BEHIND the socket
Surface mounting is less aesthetically pleasing than flush

Installer Tip:

Since these are only 25mm deep, do not try to squeeze a Shelly or Sonoff relay behind a standard socket here—it will overheat. Instead, use these boxes to install 'all-in-one' smart sockets where the Wi-Fi tech is built into the faceplate itself.

Priced at £10.99 at the time of writing

Check Price on Amazon

Evoges 1 Gang Dry Lining Back Box 47mm (Pack of 5)

Problem-solving

EVOGES

When you are upgrading a whole room to smart lighting, buying singles gets expensive and frustrating. This 5-pack solves the problem of consistency during renovations.

Price£8.49 (at the time of writing)

BrandEVOGES

QuantityPack of 5

Cost per unitApprox £1.70 per box

The Good

Excellent value per unit compared to singles
Ensures consistency across a full room renovation
Same high-quality 47mm depth for smart modules

The Bad

Only useful if you have multiple points to upgrade
Same limitation: strictly for plasterboard/hollow walls

Installer Tip:

If you are batch installing these for smart switches, ensure you label your neutrals clearly. With a pack of 5, you'll likely be dealing with 2-way or 3-way switching setups; having that 47mm depth makes organising the strapper wires significantly safer.

Priced at £8.49 at the time of writing

Check Price on Amazon

Frequently Asked Questions

Why do I need a 47mm back box for smart switches?

Smart switches, or smart relays (like Shelly devices) that sit behind normal switches, take up physical space. A standard 25mm box is often full just with the household wiring. A 47mm box gives the specialized device 'breathing room' to prevent overheating and prevents crushing the cables.

Can I use dry lining boxes in brick walls?

No. Dry lining boxes rely on 'wings' or lugs gripping the back of plasterboard. For solid brick walls (common in Leeds terraces), you need metal back boxes cemented in, or surface-mounted pattress boxes if you don't want to chase out the brick.

What if I can't chase the wall deep enough?

If you have solid walls and can't chase 47mm deep (which is difficult in hard engineering brick), use a spacer frame or a surface mount box. Alternatively, locate the smart module in the ceiling rose or near the consumer unit where space is less restricted.

Are plastic back boxes safe?

Yes, provided they are UKCA/CE marked and made of flame-retardant material (like thermoplastic). In some ways, they are safer for DIY enthusiasts as they are non-conductive, reducing the risk if a wire comes loose and touches the box.

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