What is lime?

In a series of posts we’ll be exploring different materials and techniques which are natural and often low-carbon methods of construction. We often use lime in our projects but what is it and why is it good for a building?

We often use lime in our projects. But what is it and why should you use it?

Lime is powdered component of mortars and renders made from crushed and burned rocks, typically limestones and chalks. If your house predates 1950 the chances are there are tonnes of lime mortar in the brickwork of the house you live in. Mortars containing lime absorb carbon dioxide from the atmosphere that dissolves in any water present in the mortar, and reacts with the lime to produce carbonate crystals. Lime is flexible and breathable. It allows for movement in the building, preventing cracks in masonry. It also draws vapour out of masonry, and back into the air, preventing damp.

Lime mortar, used here with Cambridge Gault clay bricks, gives a course, gritty finish and complements the yellow-pink tone of the brick that is characteristic of the Cambridgeshire area and reflects the underlying clay.

Lime plaster can be used on internal walls, which is both breathable, and when finished with an unpainted paddle-brushed texture, it can pick light and shadows and change throughout the day.