It s the first line of defence against high vapour pressure air entering the roof structure and causing interstitial condensation.
Vapour barrier flat warm roof.
The notion behind a vapour control layer is to install it on the room.
A vapour control layer or vcl on a warm flat roof sits between the roof decking and the insulation.
If this is a habitable room beneath the roof then you should be constructing a warm roof as per building regulations c l.
There is no requirement for any air gaps.
Including fibreglass roof kits torch on felt and liquid rubber products everything you need for flat roofing is in one place.
If it is not a habitable space or as per the old design for flat cold roofs then you would use foil backed plasterboard which acts as a vb.
For all warm flat roofs a fully intact vapour barrier would be required on the room side under the insulation.
Provided your vapour control layer is intact then there should not be any risk of condensation.
Ideally you need to ventilate the roof and have a 50mm air gap above your.
Whether you re repairing a flat roof or laying a new one from scratch you ll find all the materials you need here.
Including flat roof vapour barrier for extra secure roofing solutions.
To use epdm for a warm deck flat roof construction solid closed cell roof insulation such as kingspan or celotex should be placed on top of the roof deck rather than in between the rafters.
A vapour barrier will then need to be installed to reduce condensation in the roof structure.
A vapour control layer helps you shield your building from the consequences of condensation condensation is generated when warm moist air rises and condenses into a liquid on contact with the cooler areas above the insulation.