Cold Pitched Roof – Between rafters only (New build, non vented)

Rockwool Flexi slab is friction fitted between and fully filling depth of the the rafter.

Counter-battens of 25 x 38 mm are mechanically fixed over the rafter.
 
And a BBA approved breather membrane is laid across (or under) the counter-battens and lapped (150 mm). Tiling or slating battens are fixed in the normal way.
 
Breather membranes
It is important to ensure that the breather membrane specified is suitable for the specific type of construction and has a BBA approval.
 
A vapour control layer should be installed on the warm side of the insulation prior to the fixing of the ceiling. Alternatively, this may be accommodated using foil backed plasterboard as the ceiling.