Hi,

I'm about to tile my bathroom floor and am after some advice.    The floor is currently standard T&G timber floorboards (on joists at 450mm centres, if I remember correctly).  I am going to install an electric underfllor heating mat as well.  My idea is as follows:

Screw biggest sheets possible of 1/2" ply to floorboards.  Overlay this with Auquapanel or Marmox (I think that's what they're called) concrete sheets, again screwed down using the proper fixings.  Apply a layer of flexible adhesive and bed heating mat into this.  Apply further layer of flexible adhesive and affix tiles to this.  Finally, grout with fexible grout.

I know I've read several posts on this site whih all seem to say that you need to use 18 or even 25mm ply on the floor.  The reason I don't want to do this is that with the added thickness of the concrete sheeting (used to prevent most of heat from heating mat simply being absorbed by wooden floor), this would take the floor level way above the height of the carpet the other side of the bathroom door.  I'm hoping that the combination of 1/2" ply and 12mm (I think) concrete sheet should be enough to provide a stable surface for the tiles.

What do you think?

Also, would you lay the ply and concrete sheet layer over the whole floor (i.e. under the shower, bath, etc.) or just over the areas that are actually going to be tiled?

It's a tiny bathroom (about 2.4m x 1.8m) so cost isn't really the issue - I just want to do the best job I can.

Any thoughts and advice would be greatly appreciated.

Jason,

Thanks mate - a very comprehensive reply.  What adhesive would you recommend for bedding the Aquapanel on?

Also, would you lay this over the entire floor (i.e. under the bath, shower tray, etc.) or literally just the areas that will be tiled?  I assume that doing the entire floor would be best?

Cheers.

Thanks Jason.

So are you  sponsored by BAL then?

we use 3/4 in t0 full inch and 1/2 inc cement board. thinset ply and cememt board and screw down with drywall screws or nail with calvanized nails. it is ready to go. and as you tile use flat part of trowell first on joints where boards meet. you wont need flex grout because the boards should not not move.  but if you already have it use it. and caulk baseboards  where it meets the floor. they make a matching sanded caulking (tec) make sure you pull the looks nicer toilets