minimum (sensible) depth for concrete floor?

[julianf]

ive got a room here with an old wooden floor which is badly decayed in places (part of a joist came off in my hand when i was investigaing)
part of the problem is the air bricks being burried due to subsequent building a long time in the past (ie i cant unblock them)

the surface under the majority of the floor is earth (undisturbed for many many years) and a small section is earth set with stone (as if stone has been compressed into it)

the walls are stone and probably do not have deep foundations & i would like to fit wet underfloor heating, and finish with some sort of wood, or wood look-a-like finish.
as i understand it, i need the following layers, but can i ask the depths needed?

hardcore w/thin sand blind
DPM lapped up at edged (walls will be covered with sika)
insualtion
screed wth 15mm JG PEX (?) ufh tubes
cosmetic finish


Across the majority of the floor there is currently 300mm to the top of the joists (bottom of the floor boards). There is less clearence where the stone has been compacted into the floor, but not loads less.

Ive just signed up, and this is my first post, but ive read a number of threads on this forum in the past, and have been impressed enough to sign up! : )
Thank you,
Julian

 

[tony1851]

The usual spec. for a solid floor is; min 150 compacted hardcore and sand blinding; 1200g dpm turned up to whatever you are doing to the walls; 100 Kingspan; 100 concrete; finish.
Any difference is best taken up by the hardcore rather than altering the thickness of the other layers.