Sarking boards are softwood boards, generally about 150 mm wide, that are attached to the rafters of a pitched roof to give extra strength to the overall structure of a building.
They needn’t be used in every application, and instead, their use largely depends on where in the country you are based and what type of construction you are building.
Firstly, sarking boards are typically used on buildings that are exposed to extreme weather conditions, such as high wind or torrential rain. This means that they aren’t very common in England or Wales, but are prevalent in Scotland due to weather variations and Scottish building regulations.
Secondly, sarking boards are only really specified for new build constructions and not refurbishments. This is because when we refurbish our attic space we tend simply to install insulation between and beneath the rafters. An entire re-roofing process would need to take place to add sarking boards, where any roof tiles or slates would need to be removed and then replaced over the top.
So, now that we’ve established where – more often than not, Scotland – and when – during new build or re-roofing projects – you need to use sarking boards, let’s take a look at a typical roof build up.
From the bottom, up:
- Insulation, which should sit either between and under or between and over the rafters to get the required U-value
- Sarking boards, placed with a 2 – 3 mm gap in between each one
- A breathable membrane such as nilvent, which eliminates the need for roof ventilation
- Roofing slates
Note that if you choose to use tiles instead of slates, this will require the use of counter battens and tiling battens over the breathable membrane to allow for water drainage and attachment of the tiles.
