Stripping old roof boarding and using OSB3 instead.

[Firkin]

Hello I am replacing the roof boarding (Sarking as we call it in Scotland) and replacing with engineered (T&G) OSB3. Do I need to use a breathable vapour barrier and if yes - does it go under or over the OSB? The covering will then be felted and slated. Much appreciate any help or advice on this one. Regarding the vapour barrier if needed, what one to choose?

Regards

Firkin

 

[catlad]

You are not going to need a vapour barrier unless your roof has a ceiling.

 

[Firkin]

Catlad, thanks for the reply. Ground floor is a garage/workshop and the roof space above it is large enough to be turned into a room of sorts for clean storage or parking the wife with her craft stuff. The underside of the joists will be 2 ply PB and the topside of the joists to be floored with the OSB3 with insulation between top and bottom. When you say a ceiling do you mean as in lining the inside of the roof space with PB?

Regards

Firkin

 

[catlad]

In that case a vapour barrier to underside of the rafters prior to plasterboarding.

 

[Firkin]

Good man Catlad and thank you very much for keeping me right on this.

Regards

Firkin