Slab floor build up

[Yorkblade]

Hi,

Can someone shed some light on my extension. I have researched pretty much all aspects and I am.90% there but the one part that keeps niggling me is the slab floor build up.
There are so many conflicting build ups that I am asking you all what has worked for you.

I was going with.
150mm hardcore
50mm sand
Dpm
100mm insulation
Ufh pipes with 70mm concrete over them.

Our neighbours are going with
125mm hardcore
Dpm
200mm insulation
100mm concrete with mesh steel and ufh in.

But i have also seen
Hardcore
Sand
Dpm
Insulation
100mm concrete
50mm screen with ufh.

Thank you all in advance

 

[Mike13]

when you have UFH you suddenly need more insulation than before, room kept at ~20 C, vs pipes below the floor with water at 40C, so the heatloss is almost double what it was before.
It also depends how big the extension is, you need to consider loss straight down as well as loss around the edges.

 

[Mr Chibs]

Mine was:

100mm hardcore
50mm sand
DPM
125mm concrete
100mm celotex
Polythene layer
UFH pipes on trays
65/70mm liquid screed.

The warm up time is quicker if the insulation is on top of the concrete, but it's not quick like a radiator.

PS make sure you have a perimeter 25/50mm of celotex upstand around the walls.