Vent 3- Breathable Membrane Technical Data
|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|
(EN 12311-1) TD
BS EN 20811)
|Water (Moisture) Vapour
Transmission (BS 3177)
|Resistance to streaming
|Water Vapour Resistance
|UV Resistance||4 months|
Vent3 must be installed in accordance with the relevant sections of BS 5534:2003 and Britmet Tileforms 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 Tileform 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
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|