what am I meant to ensure happens with the floor insulation re internal walls?

[CalvinHobbes]

I know I have read it here before but cannot find it and I think the builder is doing ours this afternoon. So we have cement slabs with a radon barrier on top (yes I know building control insisted) 150 of insulation going down with underfloor heating....so what about the edges both to external walls? I have to be very specific The radon barrier is getting redone because it inevitably ripped.

Edited September 30 by CalvinHobbes