ECN Forum Forums General Topics of the Trade General Discussion Area Membrane under slab

dmatt,
Are you talking about a layer of Alkathene sheeting as a Damp-proof Membrane?.
Personally, as far as you've explained your intended course of work, I can't fault it.
The only thing I would suggest is, that you make sure that the outer cladding (if metallic) is adequately bonded in all places and then Grounded.