An architect has drawn up building regs drawings for a proposed extension a nd the floor detail shows a vapour barrier both below and above the insulat ion under the concrete slab. Is this normal/advised? I have only ever seen the vapour barrier mentioned as going either above or below the insulation, but never any mention of doing both (or explicitly not doing so for that m atter).
I will of course ask the architect but wanted to also get a second opinion in advance from the panel.