Older Buildings: Common Slate Roof Problems
Learning how to recognise common slate roof problems is an important step in caring for your traditional building. We highlight common issues affecting slate roofs and how to spot them.
Scottish slate is our most common traditional pitched roof covering and has been for many centuries, originally on castles and grand houses. In Scotland, slate was used more commonly from the 18th century depending on location. 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. For example Welsh slate became more common from the end of the 19th century when rail transport was possible.
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 different slates and available options for slate repair contact us.
Pantiles and other roof coverings
Find out more about other traditional types of roof tile used in Scotland, such as pantile.
Common slate roof problems owners should be aware of
Missing and slipped slates
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.
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’.
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.
Slate roof problems: what you can do
Check your roof covering at least once a year and after severe weather. An initial inspection can often be done from the ground aided by binoculars or with a camera with a good zoom lens.