I intend to remove the covering from my extension flat roof (about 9 square metres) and install Celotex 126mm TD4000 (vapour control/insulation/5.5mm ply all in one) directly onto the joists and then put EPDM on top.
On the Celotex website it says that single ply waterproof layers laid on top of TD4000 usually require an additional 12mm of ply onto the Celotex board before applying the waterproof layer (EPDM).
Is this necessary? If so why?
On the Celotex website it says that single ply waterproof layers laid on top of TD4000 usually require an additional 12mm of ply onto the Celotex board before applying the waterproof layer (EPDM).
Is this necessary? If so why?