Lime render is the first coat of lime plaster applied to the external surfaces of traditionally-built stone or brick buildings.
The lime plaster allows the building to ‘breathe’ as lime is porous, it allows for the collection and evaporation of moisture. Traditional render materials, such as cement, in contrast traps moisture behind the stonework, which can result in the erosion of the masonry over time. This is why it is important to use lime render when finishing cob buildings which should not get damp.
We use natural hydraulic lime which we find sets faster and is more durable over time.
What is the difference between Hydraulic Lime and Non Hydraulic Lime?
The first thing that is important to understand is the difference between Hydraulic Lime and Non Hydraulic Lime. The main difference is that hydraulic lime sets via hydrolysis which is the reaction with water whereas non hydraulic lime sets via carbonation which is a reaction with air.
Non Hydraulic Lime is softer and more flexible than it’s hydraulic counterpart and sets at a slower rate. Hydraulic Lime sets faster and is more durable, with similar properties to cement. This makes hydraulic lime ideal for exterior work as a lime render, especially when damp conditions are expected.