What is needed in a concrete floor

What is underneath your future concrete floor? Assuming its just earth you will need:

1. An even surface - blind the surface with sand if uneven.
2. A damp proof course
3. A layer of kingspan 60mm insulation.
4. Cement and gravel mix OR ready mixed screed.
 
sanne,

To add to godthe's reply.

Under the sand should be 150mm of stone.
In your concrete screed you will have your plumbing pipes if you will have rad.s in your extension.
I would also ensure that you run 25mm vertical insulation around the perimeter walls the depth of your concrete screed - avoiding cold bridging.
You may also need to install one of those radon boxes in the stone with a 4'' pipe coming out of your external wall.I don't believe in them myself but just in case you ever wanted to sell it sounds good.
 
Thanks for the replies
Would the following be acceptable
150mm hardcore
DPM
75mm concrete
100mm insulation
radon barrier
65mm concrete
 
godthe said:
Thanks for the replies
Would the following be acceptable
150mm hardcore
DPM
75mm concrete
100mm insulation
radon barrier
65mm concrete
Click to expand...

After the hardcore put a layer of sand otherwise you could tear the DPM.
 
godthe said:
Thanks for the replies
Would the following be acceptable
150mm hardcore
DPM
75mm concrete
100mm insulation
radon barrier
65mm concrete
Click to expand...
As pointed out you should have either sand or quarry dust blinding on top of hardcore. Your radon membrane should then go in place next which will double up as a DPM. Your concrete sub floor should be 100mm at least. 150mm recommended.

You should also put in 500 gauge polythene between the screed and insulation as it has been determined that the cement in the screed can react with the insulation over a period of time.

So your makeup from bottom up would be:

Hardcore
Blinding
Radon/DPM membrane
Sub floor
Insulation
Polythene
Screed
 
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