Building

Membranes

What is a Roofing Membrane (Underlay)?

A roofing membrane, also known as an underlay, is a vital component of a pitched roof system. Installed beneath the primary roof covering, it provides temporary weather protection during construction and acts as a secondary barrier against wind-driven rain, snow and dust once the roof is complete.

Roofing membranes also play a key role in moisture management by allowing water vapour to escape while helping to reduce the risk of condensation within the roof structure. In addition, they help control wind pressures beneath the roof covering, improving the overall performance and security of slates and tiles.

Multivap Super data sheet

Multivap Plus Datasheet

Membrane Construction

Our roofing membranes are manufactured using multiple layers to deliver strength, durability and high performance:

Outer layer - A spunbond polypropylene (PP) or polyethylene (PE) layer that provides UV resistance and excellent mechanical strength.
Functional core - A high-performance microporous or monolithic (hydrophilic) film that enables water vapour to pass through while preventing water ingress.
Inner layer - A second spunbond PP or PE layer that enhances structural integrity and provides additional protection.

All Ubbink roofing membranes are rigorously tested to BS EN 13859-1 and are designed to support compliance with BS 5250:2021 for the management of condensation in buildings and BS 5534:2014+A2:2018 for wind uplift performance.

MultiVap Plus - 1m x 50m

MultiVap Plus is a vapour-permeable, highly water resistant, three-layer membrane featuring a PP spunbond membrane and microporous film. Designed for application to the outside (cold side) of pitched roof constructions, it provides effective protection against external moisture, while allowing water vapour from inside the building to escape.

Key Features

Vapour-permeable and highly water resistant
UV-resistant for up to 3 months
Marking stripes for precise positioning
High tear resistance

Find out more

MultiVap Super - 1m x 50m

MultiVap Super is a strong, vapour-permeable and highly water resistant, three-layer membrane featuring a PP spunbond membrane and microporous film. Applied to the outside (cold side) of pitched roof constructions, it helps protect the building fabric from external moisture, while allowing water vapour from inside to escape safely. This combination helps ensure the roof structure remains protected, dry, and well ventilated.

Key Features

Vapour-permeable and highly water resistant
UV-resistant for up to 3 months
Marking stripes for precise positioning
High tear resistance

Find out more

Choosing the Right Membrane for Your Wind Zone

Following new research into the wind loads experienced by roofing underlays and tiles, BS 5534 introduced a UK map dividing the country into five wind zones. While membranes are often categorised by their weight (gsm), wind zone performance is the key requirement for BS 5534 compliance. Use the guide below to select the appropriate Ubbink membrane for your project's wind zone.

MultiVap Plus

Suitable for Wind Zones 1–3 150gsm

Designed for use in low to moderate wind exposure areas, providing reliable protection and vapour permeability for a wide range of pitched roof applications.

Download the datasheet

MultiVap Super

Suitable for Wind Zones 1–4 170gsm

Our highest performing membrane, offering enhanced durability and wind uplift performance, making it suitable for all UK wind zones, including the most exposed locations.