Dry Lining Back Boxes

Aug 05, 2026 Last reply: 3 hours ago 3 Replies

Just over two weeks in the new bungalow and starting to find all the bodge jobs. Today’s issue is back boxes, the bungalow has two bedrooms in the loft with four double sockets between them mounted in the dwarf walls which are of unusual construction in that it is the first time I have seen this. What I thought was PB turns out to be 25mm thick PIR boards lined both sides with paper rather than foil with the facing side skimmed with plaster.



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Now for the bodge! Went to disconnect a small strip light dangling from its wire just above a socket. I removed the socket to find an undersized hole cut in the PIR, on the left an extra long screw was driven through the PIR with the dry lining box on the back its lugs removed and the screw driven through the back of the box. On the right the screw completely missed the box and simply held the front on by the PIR. Another socket looks like it is held on loosely in a similar way and I suspect all four are the same. Sod’s Law of course the light was not wired into the socket which only has one cable coming into it so somewhere in the void is a junction box.



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Now for the fix. I just need a quick and dirty way to get the sockets safely back into use for now, long term I want to increase the number of sockets and restoring the ring main in the process. For now I plan to open out the holes and insert Tower 47mm dry line boxes which according to SF will fit board thicknesses up to 42mm can anyone confirm this before I order them?



Richard


Quick and dirty way is to use either hot glue or expanding foam I am amazed that PIR is being used on what I presume are internal walls?

AS an aside, do not be afraid or ripping out huge chunks of the wall material - the process of wedging it back in place with hot clue and re-filling any seams is a lot less than trying to work through a laparoscopy...

Which leads to the thought that you could cut out a section of wall and replace with ordinary PB and backbox and skim over

I've probably got a couple of spares kicking around, not sure if they're Tower or Appleby though ... I'll venture into the shed.

I'd be a bit worried about their fire worthiness. On my build, it was stressed that the plasterboard needed to be 13mm to keep the fire integrity.

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