The use of building limes have increased considerably in recent years and for very good reason as these relatively simple materials are essential to the structural welfare of old buildings. Cements are the biggest single cause of dampness contributing to the decay that many historic buildings are subjected to.
Traditional building construction is based on the use of relatively soft and porous materials such as stone, brick, timber and cob, together with lime mortars for bedding and plastering. These buildings have solid walls, with no cavity, and are often built on poor foundations. They are therefore liable to settlement and movement associated with seasonal changes in ground conditions and temperature fluctuations.
Lime mortar is softer and weaker than the stone or brick that it bonds and is able to accommodate slight movement without significant cracking. Also, it is permeable and allows water vapour to pass through it. This permeability, or ‘breathing’, helps to keep the building dry inside without a damp proof course or chemical treatments.
Apart from the main advantage of allowing buildings to “breathe”, lime also has a number of other benefits:
1. It is ecological.
2. Lime mortar can protect adjacent materials e.g. timber and iron as well as stone and brick masonry.
3. When used carefully lime is exceptionally durable.
4. Disfiguring by cement can be avoided.
5. Non-hydraulic limes have an indefinite shelf life when stored without access to air.
Lime mortars, plasters, renders and limewash have been used to create hygienic surfaces and improve conditions within buildings for thousands of years.