I have a question please help
I have a new pitched roof extension being done at the moment and I am not sure the builder is correct in what he is doing.
The construction is as follows marley malvern tile on batten then breathable membrane then osb then a 45mm cavity for air flow then 90mm celotex then platerboard.
Does this make the roof a warm roof with no need for ventilation below the osb? and has the roof got to have cross ventilation above the osb for your info the outside has been finished with vented sofit board.