A waterproof membrane, commonly referred to as sarking, is installed beneath the roof battens, which support the roof tiles. Its primary function is to provide an additional layer of protection against water ingress, especially in cases where water is driven under the tiles due to wind, angled rain, or when tile joints become obstructed by debris or moss.

The sarking membrane helps to channel any water that gets through the tiles safely down into the gutter, as it is laid in a way that directs water towards the eaves.

Installing sarking is a skilled task requiring experience and care. The process involves carefully removing the existing roof tiles and battens, fitting the membrane with precision, and ensuring it overlaps into the guttering system. Once the membrane is properly secured, the battens and tiles are then reinstated, maintaining correct alignment and spacing to ensure both functionality and appearance.