Advice of retro-fit UFH in Kitchen on concrete floor

[CraigS]

Hi

 

In was wondering if I could get some feedback / thoughts on the below before I go ahead.  I am having a new kitchen-diner installed and am looking to put UFH underneath a tiled floor. I have stripped the existing flooring and the sub-floor is around 50mm below the finished flooring in the room next to it. You're probably wondering why the difference, and the reason is because we fitted retro-fit UFH to the rest of the downstairs a few years back, and installed engineered floor boards. 

 

When we installed the UFH a few years back we levelled the floor and put down overlay boards but I'm afraid to say we didn't install any insulation underneath. The advice that I got at the time was that I didn't need any as it was built into the boards, and I'm rather kicking myself that I didn't do my own research at the time. 

 

There's little I can do about that now but obviously I'd like to put some insulation down in the kitchen.

 

My plan is to

 

- seal the existing concrete floor with epoxy resin based primer

 

- install either 20mm PIR board or 20mm XPS board

 

- then 16mm XPS routed boards with a cement covering that will take the UFH pipes

 

- 8mm porcelain floor tiles

 

So that's 44mm + epoxy + adhesive which I hope is around 50mm

 

Does that sound reasonable? After some reading I think XPS might be the way to go because of the higher compressive strength?

 

If I'm going with XPS do I need the epoxy primer?

 

I'm assuming that both the insulation and overlay boards need to be stuck down. What would the recommended type of adhesive be for the above to keep the adhesive layers thin enough so that I can remain within the 50mm available 

 

 

Many thanks