Fixing a back-box onto fresh air (well, nearly)

[ToughButterCup]

The design of our (ICF -Durisol) house means that a small section of the insulated front wall is inside the house - inside the heated envelope.

And why wouldn't we need to fix a back-box into the insulated part of the wall ? ....?,

I mean come on this is our build, not anyone sensible, or someone with half a brain ...

 

As you can see, the backbox is (in this case too small - 47mm one on order) sitting on the insulation.

 

This is where the back box sits in the wall

 

 

There's just over 200 mm of insulation and then concrete behind that.

• Its naughty to put electrics next to insulation innit?
• Do I have to dig out all the insulation and plug the gap with wood or something?
• Or can I just get a jinormous screw then drill through to the concrete and fix it in that?

Or just knock the house down and start again.....

[PeterW]

Glue it to the wall then foam it in ... 

[Construction Channel]

Agreed. In the past we've made a batten that screws into the faceplate holes. Screw that batten to the wall either side to keep things flush and level. Then foam it

[Jeremy Harris]

I'd be inclined to stick a bit of thin ply to the foam (a bit of 4mm to 6mm ply would do) and then screw the box to that.  PU bubble glue works very well for stuff like this.

[ToughButterCup]

  On 28/10/2019 at 13:03, PeterW said:

Glue it to the wall then foam it in ... 

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oooooowwwww ! ? assseasy innit !

 

  On 28/10/2019 at 13:06, Construction Channel said:

Agreed. In the past we've made a batten that screws into the faceplate holes. Screw that batten to the wall either side to keep things flush and level. Then foam it

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Foam ... I like that.

 

  On 28/10/2019 at 13:07, JSHarris said:

I'd be inclined to stick a bit of thin ply to the foam [...]

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And I've even got the bubblegum errrr,     glue 

 

[ProDave]

Silly question:  Are you plasterboarding the wall?  Or "plastering on the hard?"

[Dee J]

Standard electrician's solution is some left over bonding coat plaster. Out of date bonding coat sets really quickly, so you don't have to hold the box in place very long before it's fixed.

[ToughButterCup]

  On 28/10/2019 at 15:44, ProDave said:

[....]"plastering on the hard?"

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Never ever the easy way, oh no ......

[ProDave]

  On 28/10/2019 at 16:24, AnonymousBosch said:

 

Never ever the easy way, oh no ......

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Then as above a big load of bonding plaster, mix it up thick and it should set pretty quick.

[RichS]

Muti-finish/skim plus cement 50/50 does the same