Permavent DRY+ is a vapour-permeable underlay designed for use as a secondary weather barrier in pitched roof and wall constructions. The underlay has been BRE tested and is suitable for installation across all UK wind zones, including installations with battened or taped laps at gauges of ≤345 mm, in accordance with BS 5534:2014+A2:2018 and when installed in accordance with certification requirements. It may be installed in unsupported or fully supported applications, allowing suitability across a wide range of pitched roofing and wall build-ups.
Permavent DRY+ achieves a W1 water resistance classification and provides a hydrostatic head greater than 2.0 metres, indicating superior resistance to water penetration under hydrostatic pressure, including wind-driven rain.
The underlay is available with an integrated tape system, enabling sealed laps to support airtightness, improve installation efficiency, and reduce on-site material waste.

• Vapour-permeable underlay for roof and wall constructions.
• Suitable for use with all types of solar panels.
• Suitable for use in all wind exposure zones, independent of installation method, when installed in accordance with fitting guidance.
• BBA certified 25/7479.
• DRY+ meets underlay recommendations in BS 5534:2014+A2:2018. Slating and tiling for pitched roofs and vertical cladding. Code of practice.
• W1 water resistance rating for external moisture protection.
• Superior tensile strength to withstand installation stresses and wind loading.
• Superior tear resistance, supporting integrity around fixings and penetrations.
• Integrated tape for sealed horizontal laps and reduced on-site waste.