The roof construction of the block of three houses is well under construction. The roof carcass is made up of 8×2 timbers with a number of openings for the velux windows. 18mm exterior ply has been screwed onto the timbers. Then a 50mm celotex sheet was put on the exterior plywood ( so there would be no cold bridge) with a breatheable Tyvek Supro membrane. A 2×2 timber batten was screwed down through this into the 8×2 timbers with 160mm long spax screws to form the 50mm air gap. Finally an 18mm exterior ply sheet was fixed to the 2×2 batten. This will be covered at a later stage with zinc. I have added a couple of pictures so you can see the construction of the roof build up.
Inside the building a 190mm celoxtex sheet will be put between the rafters ( a total insulation build-up of 240mm) and a tyvek vapour barrier placed in front.
Mansard Section of the Roof – Similar Construction with 18mm ply, celotex, tyvek breathable membrane, 2×2 batten and 18mm ply.