This diagram shows the traditional type of roof construction which is using a type hr underlay as i defined earlier in bs 5250.
Breather membrane roof construction.
A breather membrane prevents moisture from entering the roof space and can in some cases allow moisture to leave the roof space.
Breather membranes otherwise known as breathable membranes are used within external wall and roof constructions in order to prevent damp in buildings.
At abutments turn the underlay up by at least.
Full bba and iab approval.
Breathable roof membranes are typically used in constructions where external cladding or tiles are not completely water tight or resistant to moisture.
Roofshield provides a secondary barrier to the ingress of rain wind and snow.
Can be left exposed for up to 4 months.
It is intended for use as a pitched roof underlay breathable roofing felt and is fixed beneath tiles and slates.
Easy trim roofing construction products our products membranes breather membranes.
The breather membrane is located on the cold side of a roof s insulation beneath the support for the tiles to prevent anything penetrating the structure.
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Roofshield is a unique three layer nonwoven spunbonded polypropylene breather membrane with a patented melt blown core.
Enhances energy saving and aids airtightness.
Protection from water and moisture damage.
So this type of underlay includes traditional bitumen roofing felt as well as a more modern plastic equivalent.
With a wet verge a verge that use mortar bedding as a fixing the breather roof membrane needs to lap onto the masonry by at least 50mm.
Breather membrane defined as a membrane with a vapour resistance less than 0 6 mns g sometimes.
Some breathable membranes have sufficient air permeability that eaves and ridge ventilation of the roof is not necessary.
Related articles on designing buildings wiki.
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Durable resistance to prolonged uv radiation and high temperatures.
The channel between fixings can be used to drain moisture to the eaves.
Where a roof includes valleys ensure the breather membrane is extended by a minimum of 300mm on each side measured from the centre of the valley.
This means that insulation remains effective and the likelihood of damp and mould occurring is greatly reduced and the structural integrity of the building remains secure.
12b metcalf drive altham industrial park altham lancashire bb5 5tu.
Terms and conditions apply.
Can be used in all pitched roof constructions and some wall applications.