Breather Membranes for Roofs
You can download the TYVEK Technical Guide Roofing here.
Slate roofs are designed to shed water. Traditionally lime mortar was used to prevent wind-driven snow or rain entering the roof space. Later bitumen felt was introduced to allow rain or snow to run off without damaging the interior.The vapour permeability of bitumen felt is very poor.
With the advent of roof insulation came the requirement for felts to be breathable. Initially ” plastic ” based materials with micro perforations were used. These now need careful inspection as it was found that the perforations tended to get clogged with dust as years went by.
Improvements in roof insulation has lead to greater temperature variation on either side of the insulation. When moisture laden air hits a cold surface it gives up its vapour and the result is interstitial condensation. Tyvek construction membranes are the market leaders.
Modern energy efficient roofs should be air tight and vapour permeable. The vapour barrier on the warm side of the insulation is as equally important as the breather membrane on the cold side.
We recommend TYVEK Membranes for building construction. A pitched roof with a Cold attic needs 10mm continous opening at both EAVES. Warm attics require continous opening of 25MM at both eaves as well as the equivalent of 6mm continous opening for air to escape at the ridge. Cathedral ceilings ( insulation running as far as ridge board ) require ventilation incorporated into the ridges.
We recommend COUNTER-BATTENING to achieve a minimum gap of 50 MM between the slate and the membrane. It allows unobstructed airflow from eaves to ridge as well as reducing the risk of slate nails ( points protruding beyond the batten ) andrisk of puncturing the membrane.
HEAVY Grade slates have a RUSTIC appearance. This improves airflow between the slates all over the roof.
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