Cromar Vent 3 Light Breathable Membrane

Vent3® is a high-performance, breathable underlay designed to protect pitched roofs and wall structures from the elements while letting trapped moisture escape. With a weight of 135gsm, it offers the ideal mix of strength and flexibility—robust enough to withstand handling and weather exposure, yet light enough to install quickly and easily. This mid-weight membrane is perfect for both new builds and refurbishments. It helps prevent water ingress while allowing internal moisture to evaporate, reducing the risk of condensation build-up within the roof structure. Whether you're working on a domestic home or a commercial site, Vent3® ensures a drier, healthier roof space all year round. It’s a reliable, long-lasting choice for roofers who need breathable protection that performs just as well in wet winter conditions as it does in the summer heat.

Available Sizes

1m x 50m roll – great for smaller or more detailed roof areas 1.5m x 50m roll – ideal for covering large surfaces quickly

FAQs – Vent3® Breathable Underlay

Can Vent3® be used as a temporary roof covering?

Yes, Vent3® is durable enough to offer short-term protection during construction. However, it should always be finished with proper roof coverings as soon as possible.

Is this underlay suitable for cold and warm roof designs?

Absolutely. Vent3® is compatible with both cold and warm pitched roof systems, making it a flexible option for a variety of projects.

Do I need to tape the overlaps?

Taping is not always essential, but it’s recommended in exposed or windy areas to improve resistance against wind-driven rain and to enhance airtightness.

Check out our full range of roofing supplies.

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At JJ Building Materials, we're committed to supplying quality building products at competitive prices, backed by the service and expertise you'd expect from an established independent merchant. Whether you're a trade professional managing large-scale projects or a homeowner taking on a DIY renovation, we're here to help you find the right products for the job.

As part of the JJ Roofing Supplies Group, we build on decades of experience supplying construction materials across the UK. We've expanded beyond roofing to offer a growing range of building materials, including timber, insulation, landscaping products, plumbing supplies, flooring, doors, bricks, fencing, garden buildings and much more – all available to order online with nationwide delivery.

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