Cromar Vent3 Classic Xtra
£80.00 inc. VAT
£66.67 ex. VAT
In Stock
- Suitable For: traditional roof underlays
- Area of use: EXT
- Volume: 1m x 50m
- Type: felt
- Colour: light grey
- Brand: Vent3
- Manufactuer: Cromar
- Box Size: Single
Vent3 Classic Xtra is perfect for all types of pitched roof applications. It enables water vapor to escape from the roof structure while shielding against wind-driven rain, snow, and dust that might breach the primary roof waterproofing. This results in a durable, high-quality breather underlay that endures for the entire lifespan of the roof construction.
APPLICATION
- Vent3 Classic installation must adhere to relevant sections of BS 5534:2014+A2:2018 and Cromar’s fixing instructions.
- It serves as a secondary barrier against wind-driven rain and snow, not as the primary waterproofing layer.
- While UV stable for up to 3 months exposure, it’s recommended to apply the primary waterproofing finish promptly.
- Under slating membranes shouldn’t be relied upon for temporary weatherproof protection in occupied buildings or during internal fitting out.
- Install Vent3 Classic by unrolling across the roof, starting from the eaves, with the light grey side facing up.
- For normal slates and tiles, drape Vent3 Classic membrane 10mm to 15mm into the void between rafters and secure with tiling battens.
- In fully supported systems, lay Vent3 Classic over support and secure with counter battens, or install over counter battens and fix at 200mm centres.
- Ensure a minimum airspace of 25mm between roof sheet underlay and tiles for drainage and ventilation.
- In unventilated roof systems, use vapour control measures below the insulation layer and ensure proper building ventilation.
- Wedge abutment flashing into a mortar joint 25mm deep and at least 150mm above the level of slates or tiles.
- Turn Vent3 Classic underlay up behind flashing at least 100mm to prevent rain and snow infiltration.
- Lap joints in the membrane should follow guidelines, with 600mm reinforcing strips fixed at hips, ridges, and valleys.
- Install Cromar felt support trays at eaves to prevent ponding behind the fascia, with Vent3 laid over the tray, stopping short of roof tile tails.
- When using Integral tape membrane, align horizontal laps, remove release liner from overlaps, and firmly press the laps together.
LIMITATIONS
- Users must ensure suitability for use; Safety Data is available upon request.
- Prior to use, carefully read 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.
- 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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