Introduction to Lime Mortar Stone Repairs
Scotland has a long tradition of building with stane and lime mortar stretching back to Roman times. A large proportion of Scotland’s buildings constructed prior to 1920 used lime mortars in both construction and finishing. From the mid Nineteenth Century the use of ordinary Portland cement (OPC) mortars became increasingly common. In the Twentieth Century it became the norm for new construction, and became increasingly used to repair traditional builds originally built using lime mortar. This has a negative visual and practical impact, and can have a serious effect on the condition of the building. The construction industry has almost forgotten why lime was used, and is having to re-learn the skills to use if effectively.
In the majority of applications lime has significant performance and visual benefits over cement mortar, particularly in relation to traditional buildings. Where modern mortars have been introduced into traditional masonry structures, the consequential rate of decay can be alarming.
What is a Mortar?
A mortar is a material in a plastic state which can be trowelled into place and sets insitu. It consists of:
- A binder (lime, Ordinary Portland Cement (OPC), clay).
- An aggregate (sand or gravel).
Lime mortar mixes, whether for building, re-pointing, harling, rendering or plastering, are essentially made from the same material. Build lime is produced by burning a naturally occurring form of calcium carbonate (such as limestone, chalk or sea shells) to form quicklime by driving off carbon dioxide. This is done using a kiln and the process was once common place across Scotland.
MASONS MORTARS LTD: ARE OUR SUPPLIERS OF LIME BINDERS AND AGGREGATES