Lime has been used to build houses for over 2000 years, but in the 20th century the use of lime slowed down as cement took over for building thinner, taller masonry walls more quickly. But more recently, lime has become popular again as we’ve considered our effects on the environment and the need for longer-lasting designs. Lime lasts a long time – Roman constructions such as Hadrian’s Wall in northern England were built with lime and have since been doing their job for 1800 years.
A sustainable option
Lime is a much more sustainable alternative to common cement. Firstly, where a lime-based mortar is used the masonry can be more easily cleaned and re-used at the end of its life than where cement is used.
Secondly, producing lime-based mortars uses less energy and releases less greenhouse gas emissions than it takes to make cement. Lime binder producers are also trying to reduce their energy consumption and their CO² emissions.
Thirdly, over a number of years of being exposed to the atmosphere, lime-based mortars will absorb most or even all of the carbon dioxide given off by their production. This is something which cement-based mortars can’t do.
Designing with lime
As well as the appearance of lime-based mortars, there are a few other useful benefits to using lime as opposed to cement:
- Walls built with lime-based mortars are less likely to crack because of the natural movements of a building or increasing and decreasing temperatures.
- When a wall is covered with lime, it finds breathing much easier. With better breathability, a wall is able to let out any moisture that manages to get inside. This is great for avoiding damage to the walls and stopping mould from forming inside the house.
- Lime-based mortars suffer less from sulphate attacks, which cause cracks to appear in cement mortars.
- Microscopic cracks can be self-healed by a lime-based mortar, whereas cracks in cement tend only to get worse if they’re not noticed and fixed.
Can I use lime-based mortar?
You can use a lime-based mortar for all kinds of jobs, but you’ll need to decide whether or not you’re going to use it quite early on in the planning process as some adjustments will need to be made to the design and work programme.
A lime-based mortar can be used for all new build constructions, but they are mostly used for building masonry walls.
Some aspects of refurbishment are thought of as conservation, such as the matching of repair and replacement mortars to the original materials, but lime can also be used for building extensions or to rebuild parts of the house as part of a refurbishment project.
Conservation and repair
Lime can be used to restore old buildings which were originally built with lime-based mortar, keeping their old appearance intact.
Lime can be combined with products such as hemp to form a breathable, environmentally-friendly render. You can also create lime plasters with a finish that can be as textured or as smooth as you like, depending on how processed the added sand is.