The importance of a vapour barrier in your bituminous waterproofing system

The importance of a vapour barrier in your bituminous waterproofing system


What is a vapour barrier?

A vapour barrier is typically sheet with a waterproof film which prevents warm, humid indoor air from condensing by keeping it from touching the cooler outer layer. Condensation is caused by warm airstreams (e.g. humid indoor air), water vapours or by building moisture.  

Preventing moisture problems

Having a well-insulated home doesn’t solely depend on the quality of the insulation material used. The vapour barrier must be of equal quality and correctly installed as well, as insulation material that gets damp loses a great deal of its insulation value. Applying a moisture-regulating vapour barrier underneath the insulation on a roof rules out condensation and, hence, moisture and mould problems.

Performance goes hand in hand with application

A vapour barrier only does what it’s supposed to if applied correctly. The seams must overlap by ten centimetres and be neatly sealed. Remember to never pierce a vapour barrier to allow for pipes or cables once it’s been applied.

HIgh quality vapour barriers from SOPREMA

Looking for a high-quality vapour barrier; consider SOPREMA’s Sopravap Stick Alu Activa 2 and Sopravap Stick Alu S16.


Sopravap Stick Alu Activa 2 vapour barrier is composed of SBS modified bitumen with a composite aluminium reinforcement. The upper and lower surfaces are provided with SBS lanes alternated with non-stick lanes. This means it is quick to install and adhesive is not required for the insulation sheets.


Sopravap Stick Alu S 16 vapour barrier is a self-adhesive modified bitumen membrane with an aluminium foil and non woven polyester reinforcement. The upper surface has a sand finish and the lower surface is protected by a silicone release sheet. This vapour barrier is cold applied and therefore suitable where a flame-free application is required on steel, timber and concrete decks.


Not quite sure which type of vapour barrier best suits your project? At SOPREMA our technical sales team are there to ensure you get the right product specification within your waterproofing system. We offer design consultations, standard details and drawings, site surveys and much more.

For more information don’t hesitate to contact our experts!