Hi Guys, just about to start a job for a new client who wants UFH which I havent done before.

They have timber floorboards at present, whats the best solution, tear them up, lay ply (say 12mm), then bond insulation board (say 10mm), lay the wire and then SLC?

What would you recomend to bond the insulation board to the ply?

Cheers

Sounds about right, apart from the thickness of the wbp ply, minimum of 18mm, prime the under side and edges and make sure there's no deflection in the floor.

So you would end up with 18+10+3-4mm SLC + Adhesive + tile? Or would you go 6mm on the insulation, other wise it comes out at say 45mm depth?

How big is the floor ?
The criterea is that you have a solid floor. Seeing as you say you can take the old boards up then you have the chance to strengthen the joists in a number of ways. then add quality 18mm 0r 25mm ply.

2.4 x2.7m

I am laying 10mm polished porcelain 60x60

Originally Posted by bmf

So you would end up with 18+10+3-4mm SLC + Adhesive + tile? Or would you go 6mm on the insulation, other wise it comes out at say 45mm depth?

Yes, but your getting rid of the floor boards, so will be loosing 20 - 25mm so that takes the overall height down, and as SR says, you can add noggins to joists if needed to re-enforce the floor space to negate any deflection

Yep very true!

What would you recommend to bond the board to the ply and what slc?

Id see what the manufactureres instructions recommend. As for the SLC it will need to be a modified one such as mapei latex plan