Hi All

I am looking to get underfloor heating installed soon (sourced from uheat probably) and from reading on here I understand a 15mm sub WBP plywood floor minimum is recommended. There is currently 18mm floorboards down that seem to be in quite good shape and relatively level. Can I simply laydown 10mm Marmox tile backer boards on top of these and then lay the underfloor heating and tiles onto this?

Just seems a bit of a waste to rip out the current floorboards if not necessary. I cant really go much higher than the current floor boards and a 10mm for tile backer if I want to keep the bathroom floor in line with the hall level. Or am I best pulling out the floorboards and replacing them with the plywood?

Also prior to laying the tiles do people use self levelling on top of the Marmox / underfloor heating mats or is it considered OK to go straight on top with flexible adhesive?

Would be grateful for any feedback from the pros out there!

Thanks

You need to determine if there is any deflection in the floor first. If there is then this needs to be sorted. Lets take it from there.

The floor is pretty good, not much if any movement and is only a small area 4m2 odd.

If I was to replace the floor boards how do people deal with it when the same board goes under the wall - do you just cut the board as close as you can to the wall over a joist so it still supported? Thanks

If you can replace the floorboards with 18mm ply (or thicker) then while you have the chance it would be worth adding extra bracing to the joists in the form of noggins. this along with new ply screwed to the joists at200 -300 mm intervals should strengthen the floor substantially .

Originally Posted by siremastimus

The floor is pretty good, not much if any movement and is only a small area 4m2 odd.

If I was to replace the floor boards how do people deal with it when the same board goes under the wall - do you just cut the board as close as you can to the wall over a joist so it still supported? Thanks

the boards may just be going under the wall slightly but if not you need to cut it and put a noggin in to support the other board. if there is no deflection in the old floor you can overboard it as you said using spf adhesive and screwed at 150mm centres