Uneven concrete slab.

[Ashworth1]

hello,
I am about to lay my 100mm of insulation onto my concrete slab and then have roughly 50mm of liquid screed pumped on top (with underfloor heating pipes in the screed)
However my concrete is roughly 40mm out in places. Would it be ok to do a semi dry mix of sharp sand and cement to build up the insulation on areas that are too low?
Many thanks

 

[^woody^]

Yes you can build up the insualtion like that.

Is 50mm of screed enough cover for the insulation (normally its 75mm) and for the pipes to be set into?

 

[Ashworth1]

Thanks woody.
I have spoke to various liquid screeding company's and they all say 50mm is recommended. Thanks