Vapour control barrier needed?

Joined
4 Sep 2009
Messages
144
Reaction score
6
Location
Essex
Country
United Kingdom
Hi all,

My vaulted pitched roof is made up of 200mm rafters. Tiles on top with a breathable membrane, 100mm airgap, then 100mm foil backed GA4000. I was going to put Celotex PL4000 underneath. Do I need to add a vapour control layer in this setup?

Thanks in advance

Paul
 
Joined
21 Jan 2007
Messages
20,359
Reaction score
2,421
Location
Devon
Country
United Kingdom
You should have a vapour barrier and it should go between the plasterboard and the insulation.

Many types of Celotex have a foil back, which when the joints are sealed with foil tape forms the vapour barrier. However I don’t think PL4000 has a foil back so you should either use a separate vapour barrier membrane or use foil backed plasterboards, which saves faffing about fixing a membrane to the roof before you attach the boards, the foil being the vapour barrier.

Alternatively use an alternative to the PL4000 with a foil back.
 
Sponsored Links
Joined
4 Sep 2009
Messages
144
Reaction score
6
Location
Essex
Country
United Kingdom
Thanks. The other option put to me was 50mm Celotex under the rafters then foil backed plasterboard. Would this work and be stable?

Cheers

Paul
 
Joined
21 Jan 2007
Messages
20,359
Reaction score
2,421
Location
Devon
Country
United Kingdom
That would be fine though if the Celotex that is being used is foil backed there is no need for the foil backed plasterboard.
 
Sponsored Links
Top