Permavent Breather Membranes

The Right Choice for Your Project

Broad MeadowIn the UK all breather membranes are classified by wind zone, with the country being divided into 5 wind zones. The lowest wind speed, Zone 1, is centred around London and the south of England, through to Zone 5 covering the very far north of Scotland. When choosing an underlay, designers and installers must be mindful of the list of criteria that apply to the Zonal tables.
These are as follows:

  • The ceiling must be ‘well sealed’, as defined in BS 9250 (referred to as ‘continuous’ in BS 5534)
  • The ridge height must not be greater than 15 metres
  • The roof pitch must be between 12.5° and 75°
  • The site altitude must not be greater than 100 metres
  • There should be no significant site topography (as defined in BS 5534)

If a project falls outside any of these parameters, the wind load may be higher than the Zonal table maximum load resistance. In these cases, a wind uplift calculation is required to determine what strength the underlay needs to be. If in doubt, please contact us for further assistance.
Permavent Max All Zones and Permavent APEX membranes are suitable for use in all UK wind zones, therefore, designers and installers can have complete confidence in their use anywhere in the UK. Max All Zones can be used without tape in any wind zone. Permavent Apex 2 TX can be used in any zone as it comes with 2 integrated tapes.

Permavent MAX is a vapour-permeable underlay, produced using the latest technology to encapsulate hydrophobic film inside spunbond polypropylene layers. Because this is done in a combined 3 in 1 process, rather than simple bonding the different layers together, quality and integrity are vastly improved and Permavent can rightly claim its products to be ‘best in class’ with superior strength, breathability, flexibility and durability. At 150 grams, Permavent MAX has been tested and certified by BRE as suitable for all UK wind zones with laps either taped or battened.

Permavent APEX is a high-performance underlay, manufactured using a unique induction bonding process that achieved superb air and vapour permeability results when tested by the BRE. It is ideal for use in new-build cold roof applications and in warm roof constructions without any additional roof space ventilation.

In addition, Permavent APEX, at 180 grams per square metre, has been tested and certified by BRE as suitable for use in all wind zones throughout the UK when installed with taped laps, with integrated tape making installation a quick and easy process.