Lime has been used widely in the construction and finishing of Scotland’s traditional buildings. Cement mortars have become more widespread than lime mortars only since the 1900s.
Building limes usually take the form of a mortar, used for pointing or bedding masonry, finishing internal or external walls, or on roofwork with pantiles. It is also used as a limewash.
Mortar is a generic term given to workable material that you can trowel in place and which hardens in situ. The vital lime mortar components are: a binder, an aggregate and water. Additives may also be used to improve performance.
Choosing a suitable mortar for repair works is important for the conservation of traditional buildings. Using incompatible mortars can speed up masonry decay and damp problems.
Most lime mortars currently used in Scotland are based on natural hydraulic limes, sold in bags as a dry hydrate powdered lime. Other types of building lime are lime putty and hot-mixed lime mortars. These traditional methods of preparation can still be used in building and repair work today.
Using hot-mixed lime mortars may have benefits over other lime mortars. They are known for their workability, good fill, frost resistance and economy, among other qualities.
There are two main methods for preparing a hot-mixed lime mortar, both of which a skilled contractor should be able to follow with appropriate training. A number of safety issues must be considered before work begins on site.