Im fixing some tapco tiles to a roof that has 11mm osb board then battens on top. The fixing guide says I need 18mm. I have rafters that are 40cms apart beneath the osb sheet. There Is also a plastic sheet (DPM sheet as its only a field shelter) then sarkit on top of the osb board then 32 x 25mm battens. Will the 11mm board suffice?
Thanks
Thanks