Specification	Details
Manufacturer	Cromar
Product	Vent3 Pro
Roll Size	1m x 50m
Nominal Coverage	50m² before overlaps
Membrane Weight	165gsm
Construction	Triple-layer spun-bonded polypropylene
Colour	Dark Green / White
Water Resistance	Class W1
Water Vapour Resistance (Sd)	0.02m
Tensile Strength	355 N/50mm (MD), 230 N/50mm (TD)
Nail Tear Resistance	188 N (MD), 229 N (TD)
Fire Classification	Euroclass E
UV Resistance	Up to 3 months
Certification	BBA Certified

1. Prepare the roof

Ensure the roof structure is sound and free from sharp objects or debris that could damage the membrane.

2. Lay the membrane

Starting at the eaves, roll Vent3 Pro horizontally across the roof, working upwards towards the ridge. Position the membrane with the correct face upwards, following the manufacturer's installation instructions.

3. Overlap adjoining sheets

Provide sufficient overlaps between membrane sheets according to the roof pitch, exposure conditions and manufacturer's guidance. Correct overlaps are essential for effective weather protection.

4. Secure with roofing battens

Fix the membrane using suitable roofing battens and fixings. Avoid excessive tension or sagging and ensure the installation complies with the required wind uplift resistance for the location.

5. Install the roof covering

Complete the installation with the specified roof tiles or slates, following the relevant roofing standards and manufacturer recommendations.

Important: Vent3 Pro is a breathable roofing underlay, not a permanent exposed roof covering. Ventilation requirements must be assessed for the particular roof construction, and the membrane should be covered as soon as practicable.

What is Cromar Vent3 Pro used for?

Vent3 Pro is a breathable roofing underlay installed beneath roof tiles and slates. It provides secondary protection against rain, snow and wind while allowing moisture vapour to escape from the roof structure.

What is the difference between Cromar Vent3 Light and Vent3 Pro?

Vent3 Light is a lightweight 95gsm membrane, while Vent3 Pro is a heavier-duty 165gsm membrane offering greater tensile strength and tear resistance. Vent3 Pro is particularly suitable for demanding roofing applications where a stronger underlay is preferred.

Is Cromar Vent3 Pro waterproof?

Yes. Vent3 Pro achieves a W1 water resistance classification, providing effective secondary weather protection when correctly installed beneath a suitable roof covering.

Can Vent3 Pro be used on warm and cold roofs?

Yes. It is suitable for both warm and cold pitched roof constructions, including fully supported and unsupported installations.

Does Vent3 Pro need additional roof ventilation?

Vent3 Pro is highly vapour permeable and helps reduce condensation risk. However, whether additional ventilation is required depends on the roof design, insulation arrangement and applicable building standards. Always follow the manufacturer's guidance.

How much area does one roll cover?

Each roll measures 1m wide by 50m long, providing 50m² of nominal coverage. The actual area covered will be lower after allowing for overlaps and cutting waste.

Can Vent3 Pro be left exposed to the weather?

The membrane has UV resistance for up to three months, but it should be covered with the permanent roof covering as soon as possible. It should not be relied upon as a temporary waterproof roof.

Is Vent3 Pro suitable for roof renovations?

Yes. Vent3 Pro is suitable for new-build roofing, extensions, loft conversions and roof refurbishment projects where a high-performance breathable underlay is required.

Is Cromar Vent3 Pro BBA certified?

Yes. Vent3 Pro is BBA certified and designed for use in pitched roof constructions in accordance with the relevant installation requirements.