Best Socket Spacers for Shallow Back Boxes: 2025 Expert Review
Oli at OR Electrics
Fully Qualified 18th Edition Electrician
If you live in a Victorian terrace or an ex-council property in Leeds, you've likely encountered the 'shallow back box' problem. You buy a sleek new USB socket or a dimmer switch, take the old faceplate off, and realise the existing metal box in the wall is only 16mm or 25mm deep. Your new accessory needs 35mm. It simply won't fit.
The 'proper' way to fix this involves getting a chasing tool, hammering out more brick, creating a massive dust cloud, and re-plastering. However, for a simple swap, that is often overkill. This is where socket spacers (or finger plates) are a lifesaver. They extend the box outwards, giving you the extra depth needed for modern electronics without the masonry work.
In this review, I'm looking at three specific spacers that solve this issue. I've categorised them into a budget standard option, a robust quality kit with screws, and a deep problem-solver for those tricky media walls or acoustic panel installations.
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Specs vs. The Real World
The Spec: "Universal Fit"
"All single gang spacers fit all single gang sockets."
Not exactly. Whilst screw centres (60.3mm) are standard, the corner profiles differ. A square-edged spacer looks awful under a rounded-edge socket (like MK Logic). Always match the profile.
The Spec: "Included Screws"
"You just use the old screws."
Rarely works. If you add a 10mm spacer, your existing 25mm screws won't reach the back box lug. You nearly always need to buy longer M3.5 screws (40mm or 50mm) separately unless provided.
My Top 3 Recommendations
Three options to cover different needs and budgets
Schneider Electric - Lisse White Moulded, Single Socket Spacer
Schneider Electric
This is a bread-and-butter component for electricians. It provides a neat 9mm extension, which is often exactly what is needed to turn a 25mm back box into a 34mm space suitable for most USB sockets or dimmer modules.
The Good
- Specifically designed to match rounded-edge profiles (like the Lisse range)
- Anti-microbial properties (good for kitchens/high traffic)
- Very affordable solution
The Bad
- 9mm might not be enough for very deep smart home modules
- Round edges won't look right with sharp, square-edged accessories
Installer Tip:
These are designed for the 'Lisse' range, which has a slight curve. If you are fitting flat-plate or square-edged switches, this spacer will be visible and might look slightly odd. Check your socket profile first.
Priced at £3.78 at the time of writing
Check Price on AmazonAcmerota 10mm Square Spacer 2 Pack with Mounting Screws
ACMEROTA
The biggest headache with spacers is realising you don't have long enough M3.5 screws in the van. This kit from Acmerota solves that by including 40mm mounting screws. It offers a solid 10mm lift and is made from robust ABS.
The Good
- Comes with long (40mm) screws – a massive time saver
- Durable ABS construction, won't crack easily
- 10mm depth is versatile for most shallow box issues
The Bad
- Higher price point, though you get two in a pack
- Basic finish might clash with premium metal faceplates
Installer Tip:
The inclusion of screws justifies the price here. Trying to source 40mm or 50mm M3.5 screws on a Sunday afternoon is a nightmare. Keep a pack of these in the drawer if you are planning to upgrade to smart switches.
Priced at £9.99 at the time of writing
Check Price on Amazon1-Gang 20mm Black Single Socket Spacer - Wall Box Extender
Alchemy Collectives
Sometimes a standard 10mm spacer isn't enough. If you have installed acoustic slat panels, thick tiles, or have a severely sunken back box, this 20mm extender is the solution. It is UK-manufactured via 3D printing and offers huge clearance.
The Good
- Massive 20mm depth solves extreme installation issues
- Perfect for bringing sockets flush with new acoustic wood panels or tiles
- Internal dimensions optimised for smart home modules
The Bad
- Black colour is specific – best for dark walls or industrial looks
- 3D printed texture is different from moulded plastic
Installer Tip:
This is brilliant for the current trend of media walls with slat cladding. If you fit the cladding over the plaster, your existing socket is suddenly 20mm too deep. Use this to bridge the gap safely without rewiring the back box.
Priced at £6.49 at the time of writing
Check Price on AmazonFrequently Asked Questions
Why do I need a socket spacer?
Are socket spacers safe?
Do spacers come with longer screws?
Can I use spacers in a bathroom?
I have old Leeds Victorian brick walls, are these suitable?
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