Vapour Control Layer For Warm Flat Roof

The notion behind a vapour control layer is to install it on the room side of the insulation so it stops the passage of warm moist air entering the structure.

Vapour control layer for warm flat roof.

The roof is an unventilated warm roof design finished with a single ply membrane. A vcl is always used as close to the inner face of a wall as possible and reduces the amount of moisture passing through the layer to low levels ensuring only insignificant amounts of condensation occur within the structure. Condensation is generated when warm moist air rises and condenses into a liquid on contact with the cooler areas above the insulation. This could be a 1000 gauge min polythene sheet.

Include at least one layer of bitumen roofing membrane s2p3 below the insulation fully bonded or mechanically fixed to the structural deck as appropriate or a suitable self adhesive or torch on membrane. It has transpired that there is no vapour control layer fitted. A vapour control layer helps you shield your building from the consequences of condensation. If this has not been done then we would recommend that you install one underneath the joists before the plasterboard goes up.

We provide a vapour control layer for flat roof installations as well as heavy duty vapour control layers for a warm flat roof. With any warm flat roof detail such as this a vapour control layer should have been laid on top of the roof deck underneath the insulation. A vapour control layer or vcl on a warm flat roof sits between the roof decking and the insulation. This is known as a vapour control layer vcl or a vapour retarder.

It s the first line of defence against high vapour pressure air entering the roof structure and causing interstitial condensation. The architect plans stated requirement for a vapour control layer below the insulation or a 3 in 1 insulation board including vapour control layer and an additional foil backed plasterboard. Because of this the vcl always sits at the warm side of the insulation. A vapour control layer is designed to catch this vapour preventing it from condensing on the insulation or elsewhere in the loft space or attic.

Vapour control layers should be provided to warm roofs and. Including fibreglass roof kits torch on felt and liquid rubber products everything you need for flat roofing is in one place. Be it a cold or warm roof construction the primary function of a vcl is to keep warm moist air from inside the building inside the building.