Depth advice

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Guys,
Ripping up my old concrete floor (1950's house has no insulation) to install a new concrete base, insulation & screed including wet underfloor heating.
I will be ripping down initially 75mm for screed, 100mm insulation and 100mm for concrete base.
Question is how much depth should I allow for the sand/dpm/hardcore base? The floor is approx 17m2.
Thanks
 
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Working top to bottom
1. 75mm screed with fibre reinforcement.
2. WUFH
3. 500 gauge or 1200 gauge slip membrane.
4. With a P/A of say 0.5, 85mm of Celotex FF4000 will give U value of 0.22
FF4000 is specially designed for WUFH.
5. 20mm Celotex TB4000 up stand to perimeters.
6. 100mm concrete slab.
7. 1200 gauge DPM
8. 50mm wacked MOT. Not hardcore. We only blind with
12mm sand. 50mm wacked MOT will do you as your
Sub ground will be hard as old boots.
Regards oldun
 
Thanks Oldun,

Just to clarify some points please:

3. I take it the slip membrane material could be same as DPM?

4. Whats P/A ( sorry not in the building trade )

8. After I have wacked down the MOT then I lay sand on top??

Floor is approx. 17m2 I had worked out 4 ton of MOT 1 for 100mm so on your calculations Oldun would 2 Tonnes be enough? Also how much sand.

Sorry for all the questions but appreciate your time & knowledge

Thanks again
 
Jassy lad.
3. Yes. Just a different expression. Stops the cat catching fire.
4. P/A equals Perimeter/Area. Divide the area into the exposed perimeter which will give you a number between 0.1 and 1.0. This number will then decide thickness of insulation required. In your case, we assumed the two external exposed walls as being approx 8metres Area is 17ms. Divide 8 by 17 = 0.470. We called it 0.5, and the insulation and type you require is in our post above.
MOT. 1.7 tonne required at 50mm thick. Bulk bags should weigh in at 850kg, so providing you give the dog a kit kat, you should have enough with two bulk bags.
Sand. Depends whether you are going to nick it of the beach or buying it If buying it you need approx 400kg, say 16no 25kg bags.
Regards oldun :LOL: :LOL:
 
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