Lime render is made from hydrated lime, sand, and water and is one of the oldest building materials. It hardens by absorbing carbon dioxide from the air, a process known as carbonation. The render is highly alkaline, making it naturally biocidal and inhibiting mould growth. Its high capillary activity allows it to absorb and release moisture, regulating the indoor climate. Lime render is vapour-permeable and essential for restoration work on historic buildings, as it is compatible with old substrates such as natural stone or brick. It is applied in multiple layers, with each layer requiring sufficient time to set. The surface can be smoothed, felted, or given a textured finish.