Reflective foil sarking, vapour permeability and BAL ratings — choosing the right wrap for your build.
What is sarking?
Sarking is a membrane installed under roof tiles or metal sheeting. It acts as a secondary barrier against water, dust and wind-driven rain, and reflective foil versions also cut radiant heat entering the roof space.
Reflective foil vs vapour permeable
Reflective foil sarking, such as Silverwrap, reflects radiant heat and is popular in warm climates like Brisbane and Sydney.
Vapour-permeable membranes let moisture escape from the roof space, reducing condensation risk — especially important in cool climates like Canberra and in tightly sealed modern homes.
Bushfire Attack Level (BAL)
In bushfire-prone areas, sarking must meet AS 3959 requirements, generally needing a flammability index of 5 or less. Check the product's data sheet against your site's BAL rating.
Installation tips
Run sarking horizontally from the gutter upward, overlap each run by at least 150mm, and allow a slight sag between rafters so water drains to the gutter. Seal joins and penetrations with compatible tape.
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