The most common question we are asked as traditional and historical building experts is firstly, how much? Secondly, however, it’s what is lime and why is it so important?
Lime has been an ingredient in traditional building practises for centuries due to its marvellous effects it can have on a building’s internal climate and durability. Lime was also favoured for its practical applications with a wide array of materials, such as granite, brick, timber and earth, which were all readily used to construct traditional structures.
We often find lime-based products in old homes, such as within plaster, walls, chimneys and even the surrounds of buildings, such as around windows and doors.
This is key in understanding how a building should be repaired, as applying a different material, such as cement or concrete, can have profound and very-negative impacts on a building’s overall health.
During the mid-19th century, cement and concrete became readily available to the average builder, and due to its convenience, as well as its easy and simplistic style of use and application, there was a surge in construction using such materials, resulting in a decline of lime mortars found in traditional buildings.
This is why many of our buildings today feature cement mortars and pointing, as repairs were made cheaper and less time consuming using such materials.
As lime became more expensive, both as a material and also as a trade, cement and concrete became more and more prominent in the industry. This resulted in centuries of building restorations being inaccurately performed due to using the wrong materials.
Cement can often cause a house to become riddled with damp, mould and humidity that leads to a poor living condition and poorly maintained homes with rotten materials seen throughout.
Lime, however, is porous, soft and malleable, lending itself to season changes and differences in climate by allowing humidity and moisture to flow naturally through the material, leading to the term “breathable” when discussing lime, as the material in a sense allows the buildings to breath and create a steady internal climate.
Lime can come in many forms, and were seen widely in mortars, decoration materials, plasters and renders, and the revival we have seen in the last few decades of historic building practises has meant more and more traditional buildings are finally receiving the TLC they have needed for centuries.
Lime is a tricky material to use. Firstly, it is important to note that ratios and gaging is key when it comes to mixing with lime.
Lime needs to be measured correctly with other materials such as sand, as the chemical reaction that takes place when water is added to lime is what helps create the breathable and aesthetically pleasing result at the end.
If mixed improperly and too little/much water is added, the result can be a mortar that can do more harm than good to a building once applied.
Users should establish good contact with a specialist provider and/or contractor, so that they can receive specialist advice that may be the difference in a home that breathes and a home that does not.
Guides are given on most lime containers, and Legacy recommends using St Astier products, as these products are readily available from most building traders and suppliers, and their wide array of materials and products means that a consumer can use St Astier products from the start of a project right up to its completion.
These guides are incredibly useful and can often give insight into the calcification of the lime which is crucial when it comes to maintaining lime as it begins to set in and around a building.
Lime must be kept moist during the setting process, as the chemical reaction must be given water and time to properly set.
If the temperature is too low, Legacy recommends waiting until warmer months, such as March onwards and performing works no later than December.
Legacy also advises that hessian rolls be purchased and hung from the building’s facias if lime works are being performed externally.
Once hung, the fabric must be kept moist on a very regular basis—between four to five times a day.
This is to keep the lime moist and away from direct sunlight, as this can dry out the lime too quickly and result in cracking or blowing in the render or pointing.
By the end however, the lime will be porous, breathable and ready to take on all four seasons of British climate with ease, keeping buildings cool within the summer months and helping keep buildings dry and insulated during the winter months.
Lime is relatively easy to maintain, though again, users should ensure that a relatively base understanding is adopted before looking into maintenance products. These products include using fixative and SP Plus to ensure the lime is fully protected from the elements and has the proper surface layer to tackle any weather conditions.
If you wish to paint lime, it is imperative that users use breathable paints, such as lime paints, that will help the lime render and/or lime pointing to properly breath.
Not doing so could result in the lime being unable to properly expel water from the wall and as a result force moisture into the property.
Legacy advises a lime specialist be enlisted to ensure that any and all repairs are within proper historic guidelines set out by English Heritage. You can find a link to their website for proper guidelines here: https://www.english-heritage.org.uk/
If you have a traditional home that you wish to restore yourself and would like expert advice/services performed, please get in touch via our website. Our expert stone masons will guide you through the process and help you along the way to restoring your historic building.