30mm metal back box - do these exist?

[pcdj]

I'm looking to replace an existing metal 30mm single gang back box with a dual gang one, to accommodate a LightwaveRF light switch I'm fitting.

It has to be at least 30mm to accommodate the LightwaveRF modules, and I don't wish to chisel out the existing cavity to accommodate a 35mm deep box, so ideally it'll be 30mm exactly.

Why are these so difficult to find? I'm seeing plenty of 25mm and 35mm boxes but nothing at exactly 30mm.

 

[DetlefSchmitz]

They're probably difficult to find because they don't make them. Why not ust set the 25mm box 5mm back from the surface?

 

[pcdj]

Why not ust set the 25mm box 5mm back from the surface?

Mainly due to the first half of the below...

It has to be at least 30mm to accommodate the LightwaveRF modules

 

[ban-all-sheds]

25 + 5 = __________ ?

 

[pcdj]

I'm sat here reading back the responses trying to understand the context of your reply, and I now acknowledge I misunderstood what was meant by the earlier one, sorry!

Yes, I guess that's an option I hadn't considered. Any downsides to this?

 

[DetlefSchmitz]

Not really - it's a fairly standard situation.

 

[pcdj]

Fair enough.

Thank you - seems an obvious solution now you point it out; I just thought the boxes had to be set to the same depth as they currently are.

 

[ban-all-sheds]

Check just how minimal the minimum depth back-box will be - it's not unknown for manufacturers to be a tad optimistic.

Given that you've got to chisel the wall out anyway it might make sense to go deeper than their minimum because it might make things a lot easier for you.

 

[EFLImpudence]

I just thought the boxes had to be set to the same depth as they currently are.

It will be.

 

[SimonH2]

I suspect he was meaning about the front edge of the box relative to the plaster surface.
The downside to setting a box deeper is that you have to carefully build up the plaster round it - and you often find the plasterer leaves it with gaps that show from behind the fitting. When my mate was doing up his bungalow, I got some of the boxes a bit deeper than planned, and had to go round hacking out some plaster* and redoing around some of the boxes with filler.

* I figured that if I just put a little bit of filler in, it wouldn't have much key and could fall out.

 

[big-all]

I suspect he was meaning about the front edge of the box relative to the plaster surface.
The downside to setting a box deeper is that you have to carefully build up the plaster round it - and you often find the plasterer leaves it with gaps that show from behind the fitting. When my mate was doing up his bungalow, I got some of the boxes a bit deeper than planned, and had to go round hacking out some plaster* and redoing around some of the boxes with filler.

* I figured that if I just put a little bit of filler in, it wouldn't have much key and could fall out.

6mm ply/mdf/osb /any material 3mm bigger than the socket width and height another bit glued to the back 1mm smaller than the lug inserts
selotape/electrical/gaffa/any tape around the block edges
4 tiny spots off superglue to locate
wood screw in the center to remove
this gives the plasterer something to level to and the screw help you find the plug