Dormer Windows, DPM Required?

[thomp1983]

Hi all,

Tomorrow I'll be insulating and boarding the cheeks of my dormer Windows and wondered if they need dpm between the celotex and osb?

The dormers are osb construction which is then wrapped in breathable roofing membrane and then upvc shiplap cladding.

I'll be using 100m celotex between the batons with 12.5mm plasterboard over the top, I just need to know if I need some visqueen or similar directly against the osb followed by the celotex or if I can place the celotex directly against the osb?

 

[^woody^]

No DPM in that location

 

[pilsbury]

Your breather membrane on the outside will let any moisture out. Your foil backed/faced celotex which should have foil tape joining it over the studs will be you vapour barrier. Not an expert, but I think regs require 50mm over the top of the lot before plasterboard.

 

[thomp1983]

Building inspector certainly does require the 100mm covered by another 50mm, this I how its turned out