Traditional lime mortar harling in Fife, Scotland
Why use lime mortar?
Slaked lime plasters and mortars have been used for thousands of years, whereas the use of cement in construction is relatively recent. The vast majority of buildings in this country prior to 1910 would have been made using lime mortar to lay the bricks, render the outside and plaster the inside. There are many examples of these traditional methods going back hundreds of years that are perfectly sound.
Buildings made using a slaked lime mortar are more capable of withstanding vibration from traffic and the movement of the ground underneath. Lime mortar makes the ideal plaster for timber-frame and straw bale construction.
Today, slaked lime mortars and mortars made with NHL (natural hydraulic lime) are increasing in popularity with enlightened architects and contractors as a superior option to cement mortar with new builds. It is aesthetically pleasing, flexible and less prone to cracking, and it also allows moisture to be released from walls via the mortar bed. Garden designers use it in hard landscaping for the same reasons. Lime also has a lower carbon footprint than cement.
If you have a home that was built using lime mortar, it is important to understand that those who designed and constructed the house knew what lime’s capabilities were. Its breathability is an integral part of the way the building copes with moisture from the ground, rain and from the activity of day-to-day living. Its ability to cope with movement is a fundamental part of the design of the property.
Buildings constructed with lime tend to be on much lighter footings than today’s sand/cement and concrete constructions. They were often built with a “step foundation-footing” no more than 400mm below ground, and were designed to move along with the minute movements of the land. It is not necessary to attempt to keep a building constructed with slaked lime mortar rigid, as lime can move without cracking. For further details about the benefits of traditional lime mortar rough casting, contact us today
When should you use cement based products?
If a cement based product is used as a render, pointing mortar or for repairs to brick or stonework on a lime mortar building, it will not move in harmony with the rest of the structure. This will inevitably cause stress and cracking in the area worked on as well as the lime construction in the surrounding area.
Because cement mortar reduces the passage of moisture there will also be a localised build up of moisture in the lime construction causing rapidly accelerating decay.
Using modern plasters, cement renders and non breathable paints can lead to damp problems as they seal the walls, not allowing them to breathe.
If you have a period property suffering from damp, cracking or timber decay, please consider that many of those problems are easily solved by allowing the building to function as it was originally meant to. The long-term effects of using modern materials without considering the original building methods can be devastating and costly. Give us a call to find out how we can help.
“First rate work real craftsman, Harry’s work is top notch. The removal of the cement was quick and done extremely well, the pointing of the wall was amazing, there were no spaces and it was all level. I would recommend this company for any job, Harry works at a quick pace and there was no mess when the job was done. Thanks.” – By Michael76