Roof sarking is a membrane that is fitted during tile or metal roof construction. The flexible membrane is usually installed under the battens to provide thermal insulation and to prevent water and dust penetration in the roof space.
In bushfire prone areas flying embers cannot enter this space through the roof due to sarking protection. Moreover in heavy storms sarking can also act to channel moisture into roof gutters and protect a home from water intrusion.
Sarking not only acts as a protection against driving rain, but can also contribute to the energy efficiency of a home. Sarking may or may not be mandatory depending on the circumstances such as whether the home is in a bushfire prone area, the likely wind speed, roof pitch and so on, terrain category and the length of the rafter; as per the BCA 2008. The most important area to be aware of is the Terrain Category and not just the N rating. The engineer is required to take both into consideration and not just the wind speed. Factors to be reported include whether the building within 500 metres off a large body of water, a golf course, a major highway or freeway, airport, farm lands, parklands or national parks in conjunction with the AS4055-1992 / AS1170.2-1989.
In summary, sarking can provide a long term environmental benefit to a new home, as well as additional protection against water damage and dust.