Lime mortar, lime wash and lime plaster, is essential for the preservation of the fabric of our historical and vernacular heritage.

Buildings built before 1900 would not have been built with cement, but with a lime mortar. To introduce cement or cementitious mortar in these buildings is to introduce an inevitable process of decay, due to the chemical composition of cement with its high percentage of gypsum and alkalis that cause sulphate and alkali-silica reactions. Irreversible damage can be caused, especially in consolidation and pointing work, with the result that in few years serious damage could occur to structures that the march of time has not.

For surface work cement mortar does not offer the high level of breathability that lime mortar allows. Damp, rot and crumbling may occur and further damage could be inflicted by using chemical or other unsympathetic remedies. Using a cement and lime mixture as a mortar to dilute the effects of pure cement mortars will not prevent these problems. It is perfectly possible to achieve the required mechanical performance using a pure lime mortar, which would be compatible with the existing mortar and much more suitable for work on period buildings.

Often, non-specialist contractor will use incorrect materials with which they are not familiar and will try to justify avoiding using lime by presuming the cost is higher. This is often not the case and if the continuing health of the building is at stake, should cease to be a factor. Only by using skilled craftsmen who have the knowledge to carry out the work required, can we preserve our heritage for the future.