Vapour Control Barrier Flat Roof

Traditionally we ve insulated the roof panel to try and keep the temperature on the panel from reaching the dew point.

Vapour control barrier 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. Using a vapour control layer to control condensation. A vapour control layer or vcl on a warm flat roof sits between the roof decking and the insulation. 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.

In this case you need to lay a full vapour barrier on top of your flat roof deck before you lay the insulation and your flat roof covering. Condensation is generated when warm moist air rises and condenses into a liquid on contact with the cooler areas above the insulation. Provided your vapour control layer is intact then there should not be any risk of condensation. One of the few places above ground level where a complete vapour barrier should be used is in flat roofing when using foil faced pir insulation.

Best vapour barrier for flat roofs this video shows me testing the vapour barrier when we did a job late last year. A primer for the vapour barrier is recommended if you are going to glue down over the top of a surface that not sound and should also be used if its cold. In warmer weather tiles can heat up causing water vapour to form beneath them in the roof cavity. But a preinstalled membrane may be even more effective at removing condensation.

A vapour control layer helps you shield your building from the consequences of condensation. We ll add a vapor barrier so the moist air does not flow up through the insulation and condense on the roof. Including fibreglass roof kits torch on felt and liquid rubber products everything you need for flat roofing is in one place. 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.

There is no requirement for any air gaps. For all warm flat roofs a fully intact vapour barrier would be required on the room side under the insulation.