UFH installation - screeding



i am installing UFH in the kitchen. the house floors are concrete on the ground floor. i have taken up the layer of modern ceramic tile, a layer of screed, the old clay tiles, another layer of screed and am now into the brick and sand base the builders originally put down in 1910.

i need to take up about 7cm of this base, but am concerned this is quite important for the foundations of the building. i have done a trial hole and this base covering is 15cm approx thick. Should i be concerned?

2nd question is should i lay down a thin screed over this rubble (say 20mm) on which to sit the insulation then the 65mm screed. or will a blinding of sand be adequate. i will be using a membrane as well.
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building control have just been - nice and early too. the floor is not structural so all ok. off to dig the bugger up now !
5 Jul 2006
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United Kingdom
Good luck digging it is my least favourite past time.

I take it you are putting in insulation and a vapour shield? I would go a bit extra and use extruded polystreyne rather than jabbalite as this will assist your ufh considerably.

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yes i am using 75mm celotox. all done today and i will do a thin screed tomorrow for the celotex to sit on.


can anyone answer this query.

i read that it is best to put a concrete base down THEN a screed of sand/cement on top. this is all on top of compacted hardcore.

i have laid a screed of 1"-3" onto the old hardcore rubble in places and also soil (i have removed all the old tiles/screed and rubble to accommodate what i am putting back).

the 75mm insulation boards will go down next (inc visquene) and then a screed of 65-70mm.

Will this be good enough?

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