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The roof is one of the most important parts of a traditional building but is often the most neglected due to accessibility issues. Checking your roof regularly is important to ensure your building remains wind and watertight.
Scottish slate is our most common traditional pitched roof covering and was commonly used from the late 18th century. In Stirling, slate from quarries along the Highland Boundary fault (commonly referred to as Aberfoyle slate) was used. Depending on the age of your building it may have a different slate such as Welsh slate which became more common from the end of the 19th century.
Slate is very durable and can be expected to last for up to 100 years or more. In Scotland, slate is traditionally fixed to timber sarking boards using a single nail at the head of the slate. The top edges of the slate are trimmed to form ‘shoulders’. This allows individual slates to be swung to one side to allow access to remove and replace any broken slate without disrupting those surrounding it.
Scottish slate is no longer quarried so repair relies on stocks of reclaimed slate.
For more information on repairing slate roofs read the HES Inform Guide ‘Repairing Scottish Slate Roofs’.
Look for a gap in the pattern of the slate covering or slates sitting in gutters. This is generally the result of bad weather. Keep an eye out for slates cracked by wind uplift.
Slates may have slipped out of line with the pattern of the roof. This may be due to nail breakage or enlargement of the nail hole as a result of natural decay.
If you have a number of broken, fractured slates or pieces coming off the roof or into the gutter, the slate may be reaching the end of its useful life and becoming ‘soft’. As a natural stone, slate will absorb water over a very long time and eventually start to break.
The original nails used to fix slates were often made of iron or poor quality galvanised steel and will corrode over time. Corrosion can cause nails to snap allowing the slate to slip. When this can be detected in a number of slates across a roof it is termed ‘nail sickness’.
Your roof may have other types of covering such as lead. HES has a series of Inform Guides on roofing including ‘Roofing Leadwork’.
Flat roofs may be covered with a modern bitumen felt. This has a short life of around 20 years and can soon become cracked allowing water ingress. Lead is a better option for the majority of flat roofs. Contact the TBHC team for advice.
Lead roofs are sometimes replaced in bitumen due to cost. If well-maintained they can have a life of around 20 years but where possible, lead should be used. For listed buildings any change in material will require listed building consent.
Here the gutter around the flat roof has become blocked with leaves. It is essential that gutters are kept clear so that water flows into the gutters and away from the roof and masonry.
In this roof, debris and soil has accumulated in the corner allowing grass to grow and block the outlet. This would encourage water to pond on the roof and possibly cause water ingress and compromise the bitumen felt.
If you are doing comprehensive repairs to your roof you may need Listed Building Consent or Planning Permission if you are in a Conservation Area. See the Stirling Council Supplementary Guidance on Roofing for more information.