I'm about to rebuilt a flat roof of a bathroom extension.
The current roof is of the "cold" type: having the insulation directly above the ceiling. I'm getting an idea of how to build a warm flat roof, but I'm still very doubtful about some points:
The Vapour control: There are rolls available which have a gauge of
300...I already have a DPM gauge 1000, can I use that instead? Beside the membrane is a single unit, I wouldn't need to join the different section together.
I have a few Kingspan board insulation (urethane with aluminium foil on both sides)....are these adequate? Would the foil interfere with the Vapour Control membrane? Can I just use the board without the membrane?
Any suggestion appreciated.