Hello chaps

Looking for a little advise, I,m building an on-suite which will be a wet room upstairs.

I am double boarding the floor, batons along the joists with 18mm chipboard in between then top of this goes another layer of 18mm chipboard (the original floor) then a further layer of 6mm ply to lift the level to that of the wet room ply former which is 24mm thick.

The floor is pretty flat between the joist, maybe a couple of mm low in a couple of areas so should I pour some levelling gear across the first layer of boards then drop on and screw the second on or just paint with PVA and screw it all together?

Cheers Mark

Are you tiling on top, and if so, is it likely to get wet? If so Wedi board or tile backer board might work better. I think both are 6mm.

Either way a couple of mm can be taken up with tile adhesive.

Stu

I,ll be fully tanking the room with epoxy matting then tiling floor and walls, having tiled on a suspended floor I know all about the floor moving and grout cracking so going a bit OTT on this room.

Just finished one,.. Glue and screw, make sure you tank completely, when tiling use a flexible waterproof adhesive wickes stuff pretty good. 40kg for £35 apply with a large notch trowel. This will help take out the uneven floor. Check with a bubble first before starting so you know where the dips etc are.

6mm ply isn't thick enough to tile onto, infact ply is not the best at any thickness. i use marmox tile backer boards available at lots of thickness's including 6mm. they also have some insulation properties to them.
screw/ stick them down using the correct washers, lay the heat mat and then self level over the lot. as well as leveling the floor it also protects the heat mat while your tiling.
if no UFH forget about self leveling if its only a few mm and sort that with the adhesive although with the cheapness of heat mats i don't see the point of tiling it without one. its years since i tiled a floor without some type of UFH.

as above flexible adhesive and also flexible grout but your probably better of going to a local tile shop that supplies to the trade.

If you are tiling over wood the adhesive is so important, have a look at : ardex 7001

If you are not used to tiling mix in smaller amounts, it's the best adhesive I have used for wood.

Although given the choice I would use 12mm backer board and then the flexible adhesive and grout.


Roger