Best way of fixing boxes to crumbly walls.....

[LewisM]

Hi I'm doing a rewire of an old victorian terraced house built in the 1890s the plaster and bricks are extremely fragile even with a hammer and scutch chisel the brick just crumbles away leaving no solid fixing, what is the best way of fixing boxes back square? I've thought about expanding foam but will that not expand and push the boxes back out?

It's hard to see from the picture but the brick is all jageded and in pieces.

 

[WallaceP]

I would use gripfill or something similar. If you need lots I would get the adhesive they use for dot and dab walls

 

[Baddegg]

Pva it and then use some bonding, might have to screw a pice of timber across the front as well…..once dry they’ll never move,most all houses down here are victorian or older and that’s how I do all of em

 

[brianmoooore]

A technique I've used in the past is to take a 12" - 18" length of batten, drill a couple of 4mm holes in it at the same spacing as the holes in a fitting, then use 3.5mm screws to attach the batten to the front of the box.
Offer this up to the wall, and nail, wedge, prop or any way else you can think of the batten flat against the wall. Mix up some mortar and pack around the box.

 

[nicebutdim]

Expanding foam will grip very well, but make sure to use a low expansion variety.

CT-1 or similar might also be a good option.

Think I prefer the idea of bonding after priming with dilute PVA.

 

[Dustydazzler]

recently Done a few new sockets in a really old crumbly house and I used coving adhesive as an emergency from wickes and that stuff sticks boxes in beautiful and it was cheap as well

 

[LewisM]

recently Done a few new sockets in a really old crumbly house and I used coving adhesive as an emergency from wickes and that stuff sticks boxes in beautiful and it was cheap as well

I'll give it a go, so just splat a load in the back then push the box in the it holds it firmly while it dries?

 

[Dustydazzler]

I'll give it a go, so just splat a load in the back then push the box in the it holds it firmly while it dries?

That is how I did it , make sure you scrap off any excess when its still wet as the stuff dries rock hard

 

[LukeD]

If thats ground floor dont use bonding .Use hardwall . Bonding will soak up moisture

 

[telectrix]

Good box in with some adhesive begged off the dot and dab monkeys.

 

[Vortigern]

Bonding plaster with a screw in the centre is my preferred method.

 

[davesparks]

Spray it with water and slap some bonding in there.

If you want it to go off quick mix a bit of cement in with the bonding and it'll go off in no time.

 

[buzzlightyear]

Cement mixed with plaster goes off quick. Drat beaten to it above.

 

[Intoelectrics]

As all the above ^^^^

In the past I have used a couple blobs of grip fix to stick all the boxes in position then filled round them after with either bonding or drywall adhesive. This way you can get all the cables in then do the back filling all in one go.

Be sure to prime the brick first ideally with a very watered down pva mix.

 

[Megawatt]

Hi I'm doing a rewire of an old victorian terraced house built in the 1890s the plaster and bricks are extremely fragile even with a hammer and scutch chisel the brick just crumbles away leaving no solid fixing, what is the best way of fixing boxes back square? I've thought about expanding foam but will that not expand and push the boxes back out?

It's hard to see from the picture but the brick is all jageded and in pieces.

View attachment 103260

What about surface mounting all boxes and sleeve it up the wall or across the wall using PVC conduit