What Sub Flooring To Use On Joist With Ufh

[scott1958]

Hi, I have a traditional 1960 house, I am adding an extension and I am paying a professional to tile 35sq m with marble, we have taken the floor back to joists, I am installing water based underfloor heating, the heating sits on insulation and the spreader plate will be in contact with the bottom of the floor

The tilers in my area only have experience with UFH in screed

my question is how to I build up the floor, 20 year ago I did the same thing (with out heating) using chip and 25mm ply, screwed every 6 in

would chap and ditra be sufficient

should i lay 18mm ply on to joist for stability, then dita matting ?

or chips for coverage, then play, then ditra

cost is not the issue, quality is

 

[scott1958]

PS should I be considering the extra weigh of 20mm marble?

 

[Ajax123]

Why not ditch the spreader plates and use a screed to give you thermal mass and to generate thermal inertia so your system is more responsive and more efficient.

 

[Dan]

I'd agree with Alan above. If you use a screed you end up with a nice even heated floor that stores some heat and doesn't need to be so on / off / on / off / on / off which just stresses the manifold and joints more than is needed.

 

[scott1958]

Why not ditch the spreader plates and use a screed to give you thermal mass and to generate thermal inertia so your system is more responsive and more efficient.

I did see this apprich but I was thinking the weight of screed being held up by insulation over the next 20 year would be a source of creep and I would not see what was going on, as this UFH is being installed by a professional, of the 3 companies I approched no one offers this solution

What about the covering ply or chip, we a thinking of moving back to tiles tiles Due to weight of stone ?

 

[Old Mod]

If you're genuinely concerned with weight issues, and are considering tiles as an alternative, why not choose a 3D printed Marble Porcelain-Thin?
The manufacturer is a member here and here is a couple of examples. Standard format is 1200x600, other sizes are available,
i.e 900x900 & 1800x900
.....and what's more they're only 4.8 & 5.5mm thick respectively
Then you could have Architrave's, skirtings and whatever else takes your fancy in the real marble, if that's to your taste.

This first image is just to put their size into perspective.

......and so it goes on, a massive selection of designs.
Of course the designs vary from what u see here to basic bold colours.

 

[Ajax123]

here you go... this is what I did in my house. I used laminate rather than tiles but could have tiled just as well