Metal back box / big gap to plaster in front

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I'm fitting a fused spur at the moment and I took off the 2-gang socket I was going to spur from and was presented with this behind the socket (photo below)

There is a metal back box screwed to the block wall, with quite a gap between it and the front face of the plaster. The face plate had extra long screws to reach all that way.

Is this ok?


Also, whilst there is an earth connector on the back box, the electrician hasn't used it. Is this ok?

Some other factors:
- 2009 new build
- this isn't a dot and dab wall, this has metal vertical rails, don't know if that affects electrical regs?

Thank you all, these forums are a godsend
 
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Those metal studs are fairly common, don't worry about them.

As for your box, it looks like a 25mm box, you could try changing for a 35mm or 47mm box, this might get the box to sit flush to the plasterboard.

If there is one fixed lug on the box (which your box has) you do not need the earth flylead. You can add one if you like, but no need. If you can get your box to sit flush to your socket front, you'll get a better earth connection anyway
 
There is a metal back box screwed to the block wall, with quite a gap between it and the front face of the plaster. The face plate had extra long screws to reach all that way.
Is this ok?
Yes.
You could put a block behind it or replace it with a deeper one or a plasterboard plastic one but what would be the benefit?

Also, whilst there is an earth connector on the back box, the electrician hasn't used it. Is this ok?
Yes.
Again, you could add a length of green and yellow from socket to back box for belt and braces.

this isn't a dot and dab wall, this has metal vertical rails, don't know if that affects electrical regs?
Do you have to run the cable through a stud (vertical rail) to connect the new socket?
 
IMO It's one thing to have a bit of plaster exposed between the box and the socket but from the looks of your picture it's much worse than that. The back of your socket looks like it will be completely exposed to the void behind the plasterboard. Anyone trying to fish something through that void risks coming into contact with the live terminals of the socket.
 
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IMO It's one thing to have a bit of plaster exposed between the box and the socket but from the looks of your picture it's much worse than that. The back of your socket looks like it will be completely exposed to the void behind the plasterboard. Anyone trying to fish something through that void risks coming into contact with the live terminals of the socket.
Indeed. In fact, it doesn't look as if the socket would in any real sense be "in" the back box at all - which, as you say, is somewhat less than ideal. There will probably also be enough of a gap for a mouse, let alone massive spiders, to get into the box!

Kind Regards, John
 
In fact, it doesn't look as if the socket would in any real sense be "in" the back box at all - which, as you say, is somewhat less than ideal. There will probably also be enough of a gap for a mouse, let alone massive spiders, to get into the box!
I did consider all that before my reply, anticipating the subsequent replies, but could not think of any particular way this was different than other circumstances.

Mice can chew the cable outside the backbox. It would probably be better if they did it near the socket.
Frequently there are other knock-outs missing from back boxes for spiders.

Are you and others stating this is not allowed or just 'does not seem right' but doesn't really matter.


Are those things the actual purpose of the back box - even when completely surrounded by masonry (buried) - bearing in mind that plastic back boxes have a large hole in them.
 
I did consider all that before my reply, anticipating the subsequent replies, but could not think of any particular way this was different than other circumstances.
I suppose that, as I implied, it differs from the usual situation in that the socket, and its terminals, are not real "in" the back box - whether that matters or not.
Mice can chew the cable outside the backbox. It would probably be better if they did it near the socket.
They can (you don't need to tell me :) ). However, I was thinking more of them meeting their end trapped behind the socket and then, from the grave, tormenting one's RCDs!
Are you and others stating this is not allowed or just 'does not seem right' but doesn't really matter.
I certainly haven't said that it's not allowed, and (without thinking/looking too deeply) I can't off the top of my head think of why it would not be 'allowed'. ...
Are those things the actual purpose of the back box - even when completely surrounded by masonry (buried) - bearing in mind that plastic back boxes have a large hole in them.
Indeed. I'm not at all sure that BS7671 has anything to say about back boxes (or the lack of them). When I moved into my present house, many moons ago, I inherited a number of sockets and light switches which were simply screwed to walls (both masonry and lath/plaster), and in some cases skirtings, into which holes had be cut but no back boxes installed. As you suggest, it just "did not seem right", so I put back boxes in - but whether there was actually any (regulatory) need to, I'm not at all sure. Probably not. When one mounts sockets etc. on 'boxes' etc. (e.g. my 'check box') one certainly doesn't usually have any sort of 'back box'.

Kind Regards, John
 
Thanks for the replies everyone much appreciated.

I think this weird setup is lack of planning at first fix. The wall goes through slight curve here and I expect the thinking at first fix was that the plasterboard would be closer to the back box than it is. Evidence of this is adjacent to the plug where the metal rail holding the plasterboard has been 'fattened up' with additional thicknesses of plasterboard, which makes the wall the right shape but increases the thickness of this void.

I think I'll put a plastic backbox in as it just 'seems' right. But based on the above I'll conclude that the current setup is legal, just sub optimal?
 
Yea. Plasterers are a law unto themselves! If you can get a plasterboard box in the hole, do it, it'll certainly look tidier.
 

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