We've just bought an old cottage with a bigish (approx 35m2) flat roof extension that needs replacement (sagging boards, old felt covering etc) and the roofing contractor that did a pre purchase check quoted Â£5k + vat. for a new 5 layer felt roof with coolag insulation.
I thought that this seemed quite high so am planning on replacing it myself in the summer. After lots of reading i've decided on a fibreglass roof (mainly cause i'm used to GRP boats!) and want to build a warm roof construction.
My shopping list includes all the fibreglass material (approx 500 quids worth), CSR3 18mm decking but i'm struggling to find out what insulation board i should use (and where to source it!) for the warm roof construction as it can get a bit chilly in Dundee!
I've come across composite board that includes a 6mm ply top but i'm unsure how to use this....do i still need my 18mm deck? How do i attach it to the joists? Do i need noggins?
Can anybody point me in the right direction with this? I'd be most grateful for any help :D