Breathable Roof Membrane

What is Breathable Roof Membrane?

As its name infers, breathable roof membrane ensures your roof can breathe. Similarly to a Gortex jacket that will protect walkers or cyclists from weather conditions, these sheets allow moisture to escape from inside of the roof, at the same time as protecting buildings from weather conditions, whether it be rain, snow, wind or any condensation that may occur.

The felt is fully waterproof, is warranted to last the lifetime of the roof, will prevent condensation and allow circulation of the air.

Breathable roof membranes have been used in the building industry for many years, increasingly so in the last few years in cold pitch roof construction that do not have traditional eaves ventilation. Reduced heat loss and no need for incorporated ventilators has been a great benefit to building projects.  

Types of membrane are defined as shown below:

  • Type HR – water vapour resistance greater than 0.25MN.s/g

  • Type LR – water vapour resistance less than 0.25MN.s/g.

What do I need to consider when choosing my Breathable Roof Membrane?

Roofing membranes must be breathable, strong, waterproof, durable and flexible. These points are not easy to meet perfectly in one material, so manufacturers are targeting their products to incorporate a particular strength.

The choice of the breathable roof membrane depends on a number of factors. Location of the roof, the tile use, the pitch and baton gauge are all important points to be considered. However the perfect breather felt for one roof may be very poorly suited for another.

We no longer have to take a guess in selecting the best membrane. BBA carry out tests on most UK membranes, their certificates will help you identify which product will best meet your needs.

Does every building need breathable roof membranes?

More often than not the answer will be yes. Everything we do within the house from cooking to bathing and showering causes moisture. As the moisture rises it becomes trapped in the roof space, this can lead to mould and dampness. Items stored in the loft space will also be affected and most importantly the structure itself can become damaged which can be extremely costly to repair.