5 reasons to use a vapour barrier on your flat roof

The Vapour Barrier

When you are having a flat roof repaired or installed the most common question asked is:

“How will it be insulated?

For the UK climate, it is generally expected that a warm flat roof structure would be used to keep the room below it nice and warm and free from condensation. These days more and more of us are having flat roof extensions to use as offices, utility rooms, bedrooms, and open plan living spaces for the family – basically where people gather, and a very important layer of protection to add to the components of your roof structure will be the Vapour Barrier.

Vapour Barrier

If you choose to have a warm flat roof, the idea is to install the vapour barrier on the warm side of the insulation (in other words, on the room side of the insulation). This will in turn, restrict the flow of warm moist air from entering the structure, and so protect the room from getting damp and mould. Imagine for a moment that you are wearing a woolly jumper, you’re feeling nice and warm and dry, but then it pours down with rain. You want to keep dry so you put on a thick coat to protect you from the elements.  The combination of the wet coat with the warm moisture from your skin makes you feel damp and uncomfortable because the moist air has nowhere to go.  Imagine now that you have a layer between your jumper and coat, a wicking layer which draws away the moisture…

Cold Roof layers

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