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Sticking down celotex/Kingspan


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Established Member
18 Jan 2009
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London UK
I have recently installed Polypipe Overlay UFH throughout the ground floor of my house, as part of works including adding an extension.

It's 12mm pipe in 18mm rigid polyeurethane board, and currently it's glued down in the kitchen and rear extension, with 10mm Bamboo flooring floated on top.

I've yet to do the hall, as the floor levels are crazy, and there is no way the bamboo will survive the uneveness without hints failing etc. There was a gas pipe fitted when the house was built, which was above finished slab height, so the hall floor climbs viciously to cover the pipe, and is consequently quite concave.

I'm hoping to address this by putting down 12mm insulation over most of the floor, 6mm in a few spots, and then using self levelling compound to bring up the really curved/wonky area to this new level.

Can I just lay 12mm insulation board on the slab, and then lay the UFH board on top? Should I stick it down? What with? Would I be better off using cement reinforced insulating tile backer board (which is basically what the UFH panels are)?

Any ideas chaps?

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