Cromar Vent3 Pro Breathable Underlay
- Suitable For: Vent3 Pro is perfectly suited for all pitched roof applications.
- Area of use: EXT
- Volume: 1m x 50m 1.5m x 50m
- Type: felt
- Colour: green
- Brand: Vent3
- Manufactuer: Cromar
- Box Size: Single
Data Sheets
Vent3 Pro offers a robust solution for roofing and wall applications. Here are four key points highlighting its features and benefits:
- Heavyweight Construction: Constructed with high-tensile spun-bonded polypropylene layers surrounding a micro-porous polypropylene film, Vent3 Pro ensures durability and strength.
- Superior Moisture Vapour Permeability: With superior moisture vapour permeability, it effectively regulates moisture within the roof structure, preventing condensation and maintaining a healthy indoor environment.
- Universal Application: Designed as a universal breather membrane, Vent3 Pro is suitable for various roofing and wall configurations, offering versatility in construction projects.
- Long-lasting Protection: Its high vapour permeability and waterproof properties, combined with excellent tensile and tear strength, make it an ideal choice for pitched roof applications, providing permanent quality protection throughout the life of the roof construction.
For more information on Cromar, you can visit their website here.
Vent3 Pro is perfectly suited for all pitched roof applications. It facilitates the release of water vapor from the roof structure while shielding against wind-driven rain, snow, and dust that might compromise the main roof waterproofing. As a result, it serves as a durable, high-quality breather underlay, ensuring long-term protection for the roof construction.
APPLICATION
- Install Vent3 Pro following relevant sections of BS 5534:2014+A2:2018 and Cromar’s fixing instructions.
- Consider Vent3 Pro as a secondary barrier to wind-driven rain and snow, not a primary waterproofing layer.
- While UV stable for up to 3 months exposure, apply the primary waterproofing finish promptly.
- Under slating membranes should not serve as temporary weatherproof protection for occupied buildings or during internal fitting out; additional protection is necessary.
- Unroll Vent3 Pro across the roof, starting from the eaves with the green (printed) side up.
- For normal slates and tiles, drape Vent3 Pro membrane 10mm to 15mm into the void between rafters and secure with tiling battens.
- In fully supported systems, lay Vent3 Pro over support and secure with counter battens, or install over counter battens and fix at 200mm centres using corrosion-resistant straps or galvanised clout nails.
- Ensure a minimum airspace of 25mm between roof sheet underlay and tiles for drainage and ventilation.
- In unventilated roof systems, employ vapour control measures below the insulation layer to restrict moist air flow from within the building into the roof space; ensure proper building ventilation according to regulations.
- Wedge abutment flashing into a mortar joint 25mm deep and at least 150mm above the level of slates or tiles.
- Turn Vent3 Pro underlay up behind flashing at least 100mm to prevent rain and snow infiltration into the roof-space.
- Lap joints in the membrane should generally follow guidelines; fix 600mm reinforcing strips at hips, ridges, and valleys.
- Install Cromar felt support trays at eaves to prevent ponding behind the fascia; lay Vent3 Pro over the support tray, stopping short of roof tile tails to prevent UV degradation of the underlay.
LIMITATIONS
- Users are responsible for ensuring suitability for use; Safety Data is available upon request.
- Before use, carefully review the label for essential health and safety information.
- Exercise caution for health and safety, especially when working at height; safety is crucial for all construction workers, both above and below.
- Cromar Vent3 breather membranes should not be incorporated into a fall arrest system.
- Exposure: Vent3 breather membranes may remain unprotected for up to 3 months, but it’s recommended to install tiles or slates promptly to minimize the risk of water ingress through unsealed overlaps, edges, and nail holes. Following guidance from NHBC and BBA, it’s advisable to cover the felt within a few days.
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| Elementlength | |||||||
| up to 1,5 m |
up to 2,5 m |
up to 3,5 m |
up to 4,5 m |
up to 2,5 m |
up to 3,5 m |
up to 4,5 m |
|
| Type of window frame material |
Minimum witdth of joints for a butled mounting b in mm |
Minimum witdth of joints for a inner mounting b in mm |
|||||
| Hard PVC (white) | 10 | 15 | 20 | 25 | 10 | 10 | 15 |
| Hard PVC and PMMA (dark) (colour extruded) |
15 | 20 | 25 | 30 | 10 | 15 | 20 |
| Hard PUR integral foam | 10 | 10 | 15 | 20 | 10 | 10 | 15 |
| Wood-aluminium-window | 10 | 10 | 15 | 20 | 10 | 10 | 15 |
| Aluminium-plastic sandwich frame (bright) |
10 | 10 | 15 | 20 | 10 | 10 | 15 |
| Aluminium-plastic sandwich frame (dark) |
10 | 15 | 20 | 25 | 10 | 10 | 15 |
| Wooden window frame | 10 | 10 | 10 | 10 | 10 | 10 | 10 |
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