Confused... Cellotex under or ontop of concrete slab.

[MarkG]

Hi, I have a builder doing some work for me at the mo, a small single story porch/washroom. It's subject to planning and building regs and I believe the inspector has been visiting...

Now a couple of years back, I did a base for my conservatory, that has underfloor heating, from memory, the base was crush and run, then sand, then DPC plastic, then concrete, the some sand, then cellotex and the UFH pipes ontop the cellotex (using push-in clips), and then the screed poured over the lot (and then tiled).

I spotted today that my builder has done things different.

I don't see much evidence of crush and run, it seems like sand underneath, then DPC plastic then cellotex with the concrete being poured over that.

Is this correct? (or has he taken a shortcut?) I'm just natually a curious/untrusting person :-}

Thanks.

[sm_jamieson]

the screed is more tricky since it needs to be stronger - often has fibres added. If you are not having underfloor heating there, what he has done is fine. If you are having UFH, ask him how this will be done. See a recent thread on this matter for pros and cons. Simon.

[MarkG]

Curiosity got the better of me, there is crush and run underneath, so the only oddity, is that I used the Cellotex ontop my slab, the builder is using it under the slab. Can it be used it both ways?

[sm_jamieson]

Yes. Simon.