Cromar Vent3 Breathable Roof Membrane
- Suitable For: all pitched roof applications
- Area of use: EXT
- Volume: 1m x 25m 1m x 50m 1.5m x 50m
- Type: felt
- Colour: blue
- Brand: Vent3
- Manufactuer: Cromar
- Box Size: Single
Data Sheets
Cromar Vent3 is a robust, triple-layer fabric breather membrane composed of high-tensile spun-bonded polypropylene layers encasing a micro-porous polypropylene film.
- Heavyweight Construction: Vent3 is built with high-tensile spun bonded polypropylene layers and a micro-porous polypropylene film, ensuring durability.
- Universal Application: Designed as a universal breather membrane, Vent3 is suitable for roofs and walls, offering versatility.
- Superior Moisture Vapour Permeability: With superior moisture vapour permeability, Vent3 effectively regulates moisture within the roof structure, preventing condensation.
- 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 roof’s lifespan.
For more information on Cromar, you can visit their website here.
Vent3 is perfectly suited for all pitched roof applications. It facilitates the release of water vapor from within the roof structure while safeguarding against wind-driven rain, snow, and dust that may compromise the main roof waterproofing. This ensures a permanent, high-quality breather underlay that will endure throughout the life of the roof construction.
APPLICATION
- Vent3 must be installed following the relevant sections of BS 5534:2014+A2:2018 and Cromar’s fixing instructions.
- Designed as a secondary barrier to wind-driven rain and snow, Vent3 should not be relied upon as a primary waterproofing layer.
- While UV stable for up to 3 months exposure, it’s advisable to apply the primary waterproofing finish promptly.
- Under slating membranes are not suitable as temporary weatherproof protection for occupied buildings or during internal fitting out; additional protection is necessary.
- Install Vent3 by unrolling it across the roof, starting from the eaves with the Blue (printed) side up.
- For normal slates and tiles, drape Vent3 membrane 10mm to 15mm into the void between rafters and secure with tiling battens, ensuring sufficient space for drainage and ventilation.
- In fully supported systems, lay Vent3 over the support and secure with counter battens. Alternatively, install over counter battens and fix at 200mm centres using corrosion-resistant straps or galvanised clout nails, leaving a minimum airspace of 25mm between roof sheet underlay and tiles for drainage and ventilation.
- In unventilated roof systems, implement 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 underlay up behind the 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 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, with Safety Data available upon request.
- Prior to use, carefully review the label for essential health and safety information.
- Exercise caution regarding health and safety, especially when working at height; the safety of all construction workers is paramount.
- Cromar Vent3 breather membranes should not be utilized as part of a fall arrest system.
- While Vent3 breather membranes may remain unprotected for up to 3 months, 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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