I have been looking at a warm roof construction that has a ply sheet sitting on top of the joists and then the insulation on top of that with a second (optional layer?) of ply on top of that. There is also a vapour barrier in there somewhere?
Can anyone enlighten me on this type of construction?
I am currently building a single story extension that will eventually run across the back and down the side of our semi-detached property. I have been looking at the construction of the warm roof and am a little confused as to the construction.
Does the insulation need to be 'sandwiched'...