Originally Posted by FRG
It's block-cavity-brick and the floor will be timber joists, insulated inbetween with an 18mm chipboard deck sat on the top, UFH to be installed on top of the deck and a lam. floor on top of that. I have taken down an old conservatory which had a tiled floor on a concrete slab, this is 8" lower than my existing floor in the house and I'm bringing it up to level so using joists is easiest plus I still need to vent under the floor of the existing house which I can easily do using this route.
Expensive route and not as good as a screed!
You will need to lay a concrete oversite then the bottom of joists need to be 125mm clear of that!
I would, (far cheaper and better)
25mm sand blinding
75mm duct pipes at 2m intervals to vent existing floor
75mm extratherm insulation