Stucco finishes on walls are of three basic types: a ‘fat’ lime-and-sand mix, sometimes with animal hair as reinforcement; a hydraulic mix, containing either hydraulic lime and sand or fat lime with a pozzolanic additive and sand; and various forms of mastic. Fat lime is a pure lime with a high calcium content. Stucco became a popular material in eighteenth-century London because it makes brick buildings look as though they are made from stone. However, its use is more traditionally common in the Mediterranean region. It is vital that stucco be repainted regularly, in order to avoid frost and root penetration.