Wet UFH in old house

[Dawid86]

Hey!

I am helping my brother to install wet UFH in his house. Part of the floor is old uninsulated concrete and part is suspended floor. The suspended one is fine, we will put new timberwork lower and we have a system that then goes on top of it.
For the concrete I can't go above it as the ceiling is not very high so we will have to smash the concrete and lay new one.
What I am thinking to do:
Break current slab and excavate to the right depth
15cm mot type 1 (although I am unsure if this is needed given the soil underneath was not touched for almost 100 years)
5-10cm sharp sand
EDPM
15cm 5 to 1 ballast with cement mix
10cm insulation
UFH pipes and screed, 7cm 1-5 sharp sand and cement
Do you guys think this looks correct?
Appreciate any help!

 

[Mr Chibs]

Hi there

I did this, if it helps, from Bottom up:

100mm hardcore
30mm blinding sand
DPM
100mm concrete
100mm insulation (kingspan)
Trays for UFH pipes
Liquid screed, 70mm (plaster said if going conventional screed to go 1:3, dryish mix).

Don't forget to put perimeter insulation around the walls and UFH expansion foam.

Good luck.

 

[Dawid86]

So looks like I was going for an overkill
What mix did you use for the concrete slab? Or did you use read mix?

 

[Mr Chibs]

I used ready mix, had 30m² to lay, I used volumetric mixer, where it's mixed on the truck and you pay for what you use.

Yes, I think you could slim down some of your depths...will give you a bit more head-height.
The sand blinding can come down too, if needed, it's only to avoid puncturing the DPM

 

[Dawid86]

Thank you for your help! Anyone in here can advise on the best mix? The area we have to do is not worth getting the ready mix so we are going to mix it ourselves