Sarking in roof constructions
The term ‘sarking’ can have a number of different meanings relating to roof construction.
Sarking boards are typically softwood boards that are attached to the rafters of a pitched roof, below the roof-covering. They are typically around 150 mm wide and are used to provide additional support and strength to the overall structure.
They are used on buildings that can be exposed to high winds, heavy rain or other extreme weather conditions. As a result, they are more common in Scotland than in England or Wales. Boards tend to only be specified for new-build, not refurbishments, as this would entail a complete re-roofing with coverings being removed and replaced, and potentially exceeding the load-carrying capacity of the roof structure.
A typical roof build-up that contains sarking is as follows (from the bottom):
- Insulation (sitting either between-and-under or between-and-over the rafters).
- Sarking boards (with a gap of 2-3 mm between each one).
- Breathable membrane.
- Roof tiles or other covering.
The term 'sarking' can also refer to a pliable membrane such as a layer of felt, polystyrene or reflective foil, that insulates or reflects heat and can provide extra weather resistance. It can act as a protective second skin for the roof by helping to prevent storm-driven rain penetrating into the roof cavity. By helping to reduce draughts, it can also limit dust entering the building through gaps around downlights and vents, and help improve thermal performance.
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