Flush metal mounting boxes

matt84 · 7 Apr 2014

Hi

I'm burying some existing surface mounted sockets into the walls of our house which are brick and plaster.

However I'm looking at the metal boxes and they seem to come in a range of sizes! Could anyone tell me the standard depth of mounting box i'll be needing? Options seem like a 25mm, 35mm or 47mm.

Also forgot to ask size needed for light switches also. Thanks

Thanks!

pjcomp · 7 Apr 2014

For most uses the 25mm deep boxes are adequate. If there are a lot of wires to accommodate, or you're using slimline sockets (where all the works sit further back into the wall) go for the 35mm. The 47mm are usually only for cooker sockets (where the cable is heavier and needs more space) or shaver sockets (which need the depth for the transformer).

For light switches the 16mm is often deep enough, but I prefer to fit 25mm as standard (35mm if lots of wires) as that usually allows for a dimmer to be fitted later on - though for some dimmers you really need a 35mm.

pj

matt84 · 7 Apr 2014

Thanks!

Would 35mm be appropriate if the socket was being used to spur another double? I imagine the three 2.5mm t+e might get crowded?

Thanks

Jackrae · 7 Apr 2014

matt84 said:
Thanks!

Would 35mm be appropriate if the socket was being used to spur another double? I imagine the three 2.5mm t+e might get crowded?

Thanks

Especially with current specification for crappy solid conductors - as against the sensible stranded type we used to use.

pjcomp · 7 Apr 2014

35mm will give you more room to work if you're not experienced at fitting wires, but they also require deeper chasing out (ie more work wall bashing!!)

25mm would be adequate for what you want to do - you pays your money, takes your choice

pj

Taylortwocities · 7 Apr 2014

Also depends on the type of socket/switch you are fitting.

Don't use 25mm boxes if you are going for flat plate sockets. They arent deep enough.

phatboy · 7 Apr 2014

I would never use 25mm boxes for anything except lighting. Maybe even then 35mm.

I found with MK sockets, 25mm with cable entering from the bottom can be an issue.

If you are chasing a wall anyway, 10mm isn't much more work and worth the effort

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Flush metal mounting boxes

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