Best bathroom sub-floor material for 1st floor bathroom - For Tiles and UFH

[Oceans247]

Hi there,

I have a bathroom on the 1st floor of a terraced house. Currently, there are old wood floorboards on wood floor beams. I would like to install UFH and then tile.

What would be the best way to do this?

I had thought of removing the floorboards, laying down waterproof 18mm plywood board, then "Warmup 6mm Coated Insulation Board" then "Warmup StickyMat Underfloor Heating System" and then tiles.

I don't want the finished height of the tiled floor to be much higher than the carpet in the hall (if at all).

I am looking at the Warmup system but that is not really critical to this post. I am most interested in what I should be doing regarding the old floorboards and that fact I want to lay UFH and tiles.

Is there a cost-effective alternative to the plywood and insulation board? Perhaps one product that is a strong and insulated board?

 

[oldbutnotdead]

Start at the top then work down..
You've got your tiles, then their adhesive, then whatever thickness of screed is specified by your selected ufh system both above and below the mat, then insulation, then structural support. As it stands you have to fit all this in the thickness of your existing floorboards and hall carpet. Sounds unlikely to me.

UFH in a typical terrace bathroom is going to struggle to deliver enough heat (the usable floor space is pretty low) so you'll prob need to keep the existing heat source.

Tiled floor will look nice but will generally feel cold so i can see the appeal of ufh there.

Being a tightwad i can also see the appeal of either sanding & sealing existing floorboards or doing the same with new to give a warm, good-looking and cost effective floor.

 

[John D v2.0]

Given it's strength wood is about the best insulation you'll get. You can additionally insulate underneath in the void. If you really want to drop the height you could put 25mm ply tight between the joists on noggins, and then use thinner ply on top, therefore limiting the overall buildup. But that setup wouldn't be as rigid so does risk your tiles cracking.