Advice for Wetroom Floor - TilersForums.com

[Flintstone]

Ufh straight on the ply? I don’t think so. The insulation board is there.... to insulate and send the heat up to the tiles, not into the ply wood. The bond to ply wood is not good ether compared to cement boards or cement coated boards.

 

[NWTiles]

Waste of money even the reps & manufactures state it’s not worth using insulation Boards on wooden floors only need them on concrete floors.

You won’t get a return on investment for years. The savings on a concrete floor, pay for the boards after 2 years. So what’s the stat for wood which is a good insulator in itself it’s gonna be more like 10 years

Which is why you don’t need to use them waste of time and cash

You could even just use a product like warmup dcm pro for speed and less height which would also require no screed and is self adhesive

 

[Bill]

@NWTiles has a point re costs - this is where an independent scientist is needed to realise all the facts, pro & con.

 

[Flintstone]

Personally, I would want something inert between my adhesive and the wood

 

[SimpleSimon]

Deffinately seal slate before grouting. What sort of slate is it? Tell me it’s not riven !

Thanks for the extra comments - still reading through them - the slate is polished / honed so is very flat and smooth (much smoother than roof slates). It was from fired earth so cost a fair bit but fortunately not too big an area!

Edit: I'll let you pros fight it out about discuss what's best, but a couple more things that might be helpful to know is that I've already bought the underfloor heating mat - the wires on it are about 3mm thick.

Also, I'm not too worried about some of the heat going downwards, since the room below is the kitchen, and I've put some mineral wool insulation between the joists to help muffle sound which will insulate a bit too. There will also be a heated towel rail in the bathroom so the UFH is really to just take the edge off the coldness of the slate.

Thanks again for all the comments!

Edit 2: It looks like the height of the floor might not be an issue, since I have to build it up enough to meet the shower tray (20mm) plus 18mm WPB ply to support the shower tray from beneath (I can't put the 18mm WPB ply between the joists since there's an air duct in the way, so I'll have to put it on top of them, then the tray on top).