Flush socket installation

[Scotland89]

I'm trying to install a new socket and am having some issues fitting the 35mm pattress.

The wall is an external cavity wall with the inner leaf being only 35mm including the plaster. So I have nowhere to mount the box to!

Unfortunately I have already knocked through a small area (which is how I found out the wall is so thin)

Any recommendations appreciated.

 

[WabbitPoo]

Can I ask what your inner skin is made of?

 

[sparkwright]

I assume we are talking about brickwork/blockwork.

You could try cementing the box in. Might work, might not bearing in mind there's nothing at the back to cement to, just the edges.

Also, many metal flush back boxes have small holes round the sides. If not you can drill some. You could try screwing the sides of the box to the remaining brickwork.

 

[WabbitPoo]

I am interested as to what blockwork is only 30mm or so thick. Doesn't sound very strong! lol

 

[sparkwright]

Another possibility is getting a piece of wood, put it inside the hole.

Drill a few holes through the blockwork, and using some 2 1/2 inch long screws screw through the wall into the wood - and fix the box to the wood.

Not ideal we know, but what do you do...

 

[PrenticeBoyofDerry]

If the age of the house/property dates back 60 yearish, there is every chance that the inner leaf and inner walls are clinker blocks, and are very thin, sinking 35mm backboxes can be a bit of a headache! If you have broke into the cavity you do not want to be bridging it to the outer leaf, as you could then come across some damp issues!

 

[Scotland89]

Thanks for the quick response guys.

Its a breeze block under the plaster. On closer inspection it seems to be the voids in the blocks I've broken through to rather than the cavity.

Drilling into the sides might be a plan, also going to try a 25mm box.

 

[Scotland89]

If the age of the house/property dates back 60 yearish, there is every chance that the inner leaf and inner walls are clinker blocks, and are very thin, sinking 35mm backboxes can be a bit of a headache! If you have broke into the cavity you do not want to be bridging it to the outer leaf, as you could then come across some damp issues!

Yep spot on 60 years so I think you're right.

 

[PrenticeBoyofDerry]

You have hollow blocks as the inner leaf, another pain in the rear.
If you have not broken into the cavity, I would recommend using some drywall adhesive to set the boxes into.
http://www.british-gypsum.com/products/gyproc-dri-wall-adhesive

 

[sparkwright]

Thanks for the quick response guys.

Its a breeze block under the plaster. On closer inspection it seems to be the voids in the blocks I've broken through to rather than the cavity.

Drilling into the sides might be a plan, also going to try a 25mm box.

If the voids you have discovered are within the block itself, then it's a bit different.

You will find a solid section somewhere that you can get a fixing.

You can even put cement in some of the voids in the block, then fix to this when dry.

 

[Gaz the Sparky]

If you struggle to get a fixing you might have to stick the box in

I use a mix of bonding plaster and cement. the cement makes the bonding go of super quick you can then make the mix stiff and stick the box in. Leave it half an hour and it's solid

Rough mix of
75% bonding plaster
25% cement

The more cement you add the quicker the bonding goes off

 

[RF Lighting]

Expanding foam is your friend here. Never met a wall yet it hasn't managed to fix a flush box to.

 

[WabbitPoo]

How to use it? Squirt, push box in and secure it to stop it being pushed out again by foam?

 

[RF Lighting]

Hold the box in place by what ever means you can. wedges, tape, bits of stone, whatever, then a small bead of foam is all you need right around the box. Less is more.

Once this has gone off about half fill the void behind the box with foam and once cured it'll be rock solid. Again, don't use too much. Once you get the hang of it, it's really quick, clean and easy.

Get a proper expanding foam gun. the diy cans are less than useless.