Best Metal Back Boxes for Safe Wiring: 2025 Expert Review
Oli at OR Electrics
Fully Qualified 18th Edition Electrician
Most homeowners never give a second thought to metal back boxes—until a socket comes loose or a dimmer switch won't fit flush against the wall. In Leeds, especially in our older solid-brick properties, the back box is the anchor that holds your electrical accessories secure.
A poor quality back box can twist when screwed into uneven brickwork, strip its threads easily, or fail to provide a safe earth connection. With the rise of USB sockets and smart dimmers, standard depth boxes often aren't enough anymore, leading to crushed cables and dangerous faults.
In this review, I've selected three metal back boxes I use on jobs ranging from budget-conscious student HMO repairs to high-spec kitchen rewires. We will look at a standard budget option, a heavy-duty quality pick, and a specialist dual box for specific layout problems.
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Specs vs. The Real World
The Spec: "25mm Depth 'Fits All'"
"Standard 25mm boxes are sufficient for all switches and sockets."
Modern accessories, especially USB sockets and dimmer switches, are bulky. A 25mm box often leaves no room for wiring, risking crushed insulation. I always recommend 35mm where wall depth allows.
The Spec: "Knockouts are Easy to Remove"
"You simply tap the circular 'knockout' to create a cable entry point."
On cheap boxes, tapping the knockout can warp the entire frame, making the faceplate sit unevenly. You need rigid steel to ensure the box keeps its shape during installation.
My Top 3 Recommendations
Three options to cover different needs and budgets
Single Metal Back Box 25mm Flush Wall Pattress
Lyvia
If you are doing a standard switch replacement and space is tight, this Lyvia box is a cost-effective solution. It is a no-frills galvanised box suitable for standard lighting circuits where you don't have excessive cabling to house.
The Good
- Very affordable for bulk renovations
- Standard size fits all basic single faceplates
- Includes earth terminal
The Bad
- 25mm is too shallow for USB sockets or dimmers
- Thinner metal can distort if overtightened on uneven brick
Installer Tip:
When chasing this into brick, ensure you clear out the chase thoroughly. Because the metal is standard gauge, any debris behind it will bow the back panel and make your faceplate wonky.
Priced at £3.70 at the time of writing
Check Price on AmazonEvoges Single Metal Back Box, 35mm, 1.0mm Thickness
EVOGES
This is the sort of back box I prefer to use on my own jobs. The 1.0mm thickness means it is incredibly rigid—vital when fixing to old, uneven mortar. The 35mm depth is the 'gold standard' for modern homes, accommodating deep USB sockets and ensuring cables aren't crushed.
The Good
- Superior 1.0mm thickness prevents warping
- 35mm depth accommodates USBs and dimmers safely
- Adjustable lug helps level the socket if the box is slightly off
The Bad
- Requires a deeper chase in the wall
- Slightly more expensive than standard options
Installer Tip:
Always opt for 35mm boxes like this if you can satisfy the chase depth. It gives you room to neatly dress cables at the back, reducing stress on the terminations and preventing fire risks associated with crushed wires.
Priced at £4.99 at the time of writing
Check Price on Amazon1G+1G 25mm Metal Back Box Dual Mount
Generic
Sometimes you need two single accessories side-by-side—like a light switch next to a fused spur—but getting two separate boxes perfectly level is a nightmare. This dual 1G+1G box solves that alignment problem instantly, providing a neat, unified solution.
The Good
- Guarantees perfect alignment of side-by-side accessories
- Easier to chase one large hole than two separate ones
- Ideal for media centres or kitchen counter setups
The Bad
- 25mm depth is limiting for bulky switches
- If you mess up the levelling, both accessories fit significantly askew
Installer Tip:
Use a spirit level on the box itself before tightening the screws. Because this box is wide, even a millimetre of tilt will look very obvious once the faceplates are on. Perfect levelling at the deeper stage is crucial.
Priced at £5.92 at the time of writing
Check Price on AmazonFrequently Asked Questions
Why do I need a metal back box instead of plastic?
Is 25mm or 35mm depth better?
Do I need to earth the metal back box?
Can I install these myself?
What if my wall is too shallow for a deep box?
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