Lime render layers: An overview of their properties

Lime renders are of great importance not only to enhance the appearance of the buildings, but also to protect and preserve old masonries. They constitute a specialized system, composed of several layers, in which each of them depends on the others and carries out some specific functions in order to assure a suitable performance of the whole. Knowledge of the traditional materials and techniques, as well as the know-how, is one of the key points in the maintenance and conservation of lime renders and, by extension, of our Heritage. However, the promotion of the use of cement and the industrialization process, which in the case of Spain took place about the 1960's, caused lime mortars to fall into disuse. In this article, classical treatises as well as the state-of-the-art researches were analysed to compile the properties of lime render layers, on the whole. The knowledge of these characteristics is essential to maintain and repair the existing renders as well as to formulate new compatible ones, while assuring their durability and appropriate performance. Lime is the selected binder for these recommendations because it was widely used as drawn from the literature.