Fitting sockets into a lath and plaster stud wall

[Nigel Watts]

Does anyone have any good tips for fitting sockets into lath and plaster stud walls without resorting to plasterboard?

I was trying to install an ethernet socket this morning. Having carefully threaded the cable down the hollow wall from the roof void (with not a little smugness at avoiding the need to doing any chasing in) I tapped at the plaster where the socket is to go and ended up with this:

When my builder had installed the double socket, which is in front of a stud, he had packed the void behind with large amounts of scrunched up newspaper and then filled the entire space with a block of gypsum plaster. Being directly behind a socket this strikes me as a fire hazard. I need to fix a socket box and replaster in lime.

 

[Feltwell]

I fitted one just the other day Nigel, using my new CEL tool - the Fein Multimaster copy, as described in another thread.

I located a stud and plunge cut the hole for the new box over the stud but slightly off-centre - so that I had the stud to fix the box to, but the box overhangs the side of the stud slightly to give easy access for the cable. I then plunge cut a series of cuts into the stud to the depth of the box, and carefully chiselled away the timber.

You could do it without the CEL tool, although it would be hard to get a job as neat. I would personally start off by drilling holes at the four corners of where the box is to go, then drilling holes as close together as possible around the edge line of the box, then finally cut with a keyhole saw. I do find though that using a keyhole saw means it can catch on the laths and cause surrounding plaster to fail, hence drilling as many holes as possible first. If you want a new toy then a Multimaster copy makes the whole job very quick, neat and easy.

If you can't fix the box over a stud then your options are limited. You could use a plasterboard box, which grips the back of the lath & plaster - maybe OK for something like a data socket that won't be unplugged very often, but I certainly wouldn't use it for a power socket - the force of the socket being pushed and pulled as it is used would eventually cause the plaster to break up I reckon.

Failing that it's trying to get something behind to bridge between the 2 adjacent studs to fix your box to.

 

[Lime]

Well, looking at the hole I think the double socket needs putting in correctly too!
The laths and plaster are not suitable to hold any flush socket by themselves without additional support.

What I'd do is remove the plaster extending to each stud either side of the double socket and proposed postion of the ethernet socket.
I'd carefully cut (with chisel) the laths continuing on into the rest of the wall and make sure they are fixed properly (screw or nail).
Then I'd use a piece of plywood of suitable dimensions (from stud to stud) to take both the double socket box and the ethernet box cut into it.
I'd attach a few laths to the plywood to give grip for the plaster.
Then I'd plaster over the plywood (probably polyfilla ) before installing the sockets.

Plasterboard would not give a suitable fix to either boxes.
Wood could be used instead of plywood but plywood is normally stronger in such restricted dimensions and space.

 

[Moo]

That's the sort of really useful information typical of Ppuke. I shall store it away for future reference.
Many thanks, Lime.

 

[Feltwell]

If you're going to use Lime's suggestion of ply then a plasterboard "dry lining" back box will be much easier to fix into it than a normal metal back box.

18mm ply would be nice and strong and be close enough to the thickness of plasterboard for it to work no problem with those style of boxes.

http://www.screwfix.com/prods/36960...kets/Mounting-Boxes/Appleby-2g-Dry-Lining-Box

Mounting boxes directly into plasterboard instead of ply would not be my favoured method, but it is how many modern houses have their sockets put in.

Alternatively, if you want to save lots of filling to get the whole surface smooth, use ply as above but recess it slightly and stick plasterboard on it with grab adhesive to be level with the surrounding wall - then you've only got the joints to make good.

But - if you can locate your boxes on studs then that's best of all I reckon, and you can make good the hole with lath & plaster again.

 

[chuckey]

One immediate point, if you use a saw to cut from hole to hole, arrange that it cuts when its pulled towards you, that way you can support the L&P with your other hand. If you use a conventional saw, it will work but will tend to catch on the lathes and peel them backwards out of the plaster.
I always cut the hole as close to a stud as possible (ideally right in front of one, and notch it). then use some Heath Robinson system with blocks of wood and screws driven in at 45 degrees to fix a conventional plaster box. Plasterboard box's ears do not go back far enough to grab a lump of plaster (would it be strong enough anyway?).
Frank

 

[MdB]

If you're going to use Lime's suggestion of ply then a plasterboard "dry lining" back box will be much easier to fix into it than a normal metal back box.

18mm ply would be nice and strong and be close enough to the thickness of plasterboard for it to work no problem with those style of boxes.

This will depend on the type of dry lining box and the thickness of plaster you put over the top. I had quite some fun fitting some recently which only had a maximum working thickness of 18mm. (18mm for the ply seems way over the top to me too - I would have thought 8mm would have been fine if there was something proper to fit it to.)

 

[Feltwell]

This will depend on the type of dry lining box and the thickness of plaster you put over the top. I had quite some fun fitting some recently which only had a maximum working thickness of 18mm. (18mm for the ply seems way over the top to me too - I would have thought 8mm would have been fine if there was something proper to fit it to.)

Sounds like a dodgy brand of dry lining box! (You didn't buy them from me did you? )

You're quite right, on further thought. Plasterboard for walls is usually 1/2" - 12mm, near enough - so with a skim of plaster allowed for, some boxes probably will only go to 18mm. I do tend towards over-engineering - I would worry about 8mm ply being too flexible and the plaster "overlay" cracking with movement as the socket is used.

8mm but with a couple of timber battens fixed to the back above and below where the socket goes, no problem!

 

[michael]

Have you considered fitting the sockets to the skirting board rather than the wall? That’s assuming you have no plans to change the skirting for the next 25 years or so.
In my home , the walls are timber panelled from floor to about 4ft above FFL and the wall sockets (back boxes) have spring loaded wings on either side which retract into the back box and release out when they have cleared the hole in the timber. Screwing the face plate on the front then pulls everything together. Wonder if something like this might work for you?

 

[michael]

Researching this a bit further, I think my electrician has just installed a fancy version of a dry lining back box with adjustable lugs (springs not really required as lugs can be pushed out from within the box). Again I’m wondering if this could be installed within your skirting board?

This example fits into a plasterboard depth of up to 20mm. I wonder if you can find lugs that fit behind say 25mm thickness.

http://www.elvets.co.uk/dry-lining-back-box--47mm-deep--2-gang-flush-mount-fitting-2621-p.asp

 

[Lime]

It is a retrograde step to lower a power point and fix it to a skirting board.
Unless other sockets are already fitted in or on skirting boards in the same area it will not comply with building regulations.

 

[Nigel Watts]

Thanks for al the good ideas.

My inclination is to try to fix some kind of noggin between the studs to which the back box can be fixed:

then to try to reinstate the laths or perhaps use some metal mesh as a background for a repair with haired lime plaster.

 

[Lime]

My inclination is to try to fix some kind of noggin between the studs to which the back box can be fixed:

Even better if you have enough access and space within the wall.
The plywood could be fitted in much the same way too.

then to try to reinstate the laths or perhaps use some metal mesh as a background for a repair with haired lime plaster.

I would not recommend any metal mesh whatsoever in and around any electrical outlet, high voltage or low.

Bonding the mesh to both socket outlets or just one is not recommended either.
Earthing the mesh to the MET (main earth terminal near service head) requires further wiring and perhaps may introduce further problems.