Sarking is the use of wood panels, or "sarking boards", under the shingles of a roof to provide support. It is a common term in Scotland, Australia, and New Zealand. The shingles or slates are nailed directly to the sarking boards without timber battens, providing a strong, wind-resistant roof. The term can also refer to an additional layer within a roof that insulates or reflects heat, such as a layer of felt, reflective foil, or polystyrene.
The word sarking is further used as part of the term "scrim and sarking", a method of interior construction widely used in Australia and New Zealand in the late 19th and early 20th centuries. In this method, wooden panels were nailed over the beams and joists of the house frame, and a heavy loosely-woven cloth, called scrim, was then stapled or tacked over the top of this. This construction method allowed wallpaper to be applied directly to unplastered walls.
In current usage in Australia, sarking refers to a laminated aluminium foil layer (commonly described as RFL, or reflective foil laminate) that is installed on the roof trusses, beneath the battens, supporting a tile or metal deck roof. It acts as additional radiative and convective insulation and provides a condensation barrier.