Vent 3- Breathable Membrane Technical Data

Product Details

Roll weight kg 7.10 (+/- 5%)
Weight g/m2 142 (+/- 5%)
Roll Length m 50
Roll Width m 1
Roll Area m2 50
Colour Dark Blue Upper/White Lower

Performance Details

Tensile Strength MD
(EN12311-1) TD
Elongation MD
(EN 12311-1) TD


Nail Tear MD
(EN12310-1) TD
Hydrostatic Head
BS EN 20811)
Water (Moisture) Vapour
Transmission (BS 3177)
Fire Rating
(DIN 4102)
B2 (Pass)
Resistance to streaming water
Water Vapour Resistance
(BS 3177)
0.18 MNs/g
UV Resistance 4 months


Vent3 must be installed in accordance with the relevant sections of BS 5534:2003 and Britmet Lightweight Roofing’s fixing instructions Vent3 when installed as a fully supported system, is laid over the support and secured with the counter battens, alternatively the membrane can be installed over counter batens and fixed at 200mm centres using corrosion resistance straps or galvanised clout nails. Tiling battens are fixed to the counter battens leaving a minimum airspace of 25mm between the roof undelay and the tiles for drainage and ventalation.

Abutment flashing should be wedged into a mortar joint 25mm deep and at least 150mm above the level of the slates or tiles. Vent3 underlay should be turned up behind the flashing at least 100mm to prevent rain and snow being blown into the roof-space. Lap joints in the membrane should be generally in accordance with thetavle set
out below. 600mm reinforcing strips should be fixed at hips, ridges and valleys.

Vent3 has UV resistance for up to four months. Correctly installed it will provide temporary weather protection, prior to the application of the mainroof finish. At eaves Britmet Lightweight Roofing felt support tray should be installed to prevent ponding behind the fascia. The Vent3 should be laid over the support tray by 150mm stopping short of the
roof tile tails to prevent UV degradation of the underlay.

Lap Size Table

Roof Pitch Minimum horizontal lap Minimum horizontal lap
Not fully supported Fully supported
12.5° to 14° 150mm 225mm 100mm
15° to 34° 100mm 150mm 100mm
35° & above 75mm 100mm 100mm

Technical Information

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