The weathering of porous materials due to the presence of salts has been known since antiquity. However, serious studies and investigations were not conducted until the 19th century. One of the fi elds of interest includes historic masonry, where salt damage can affect natural stone, brick and mortar (see Figure 1). Mortars are building materials, which are for example used in masonry, as the bonding material in between bricks or stones or as a plaster or render. Because of its pore size distribution (with both coarse as fi ne pores) and its relatively low mechanical strength, mortar is one of the building materials most affected by salt crystallization damage. As a consequence, replacement of plasters, renders and pointing mortars often constitutes a large part of total restoration costs. Salts present in masonry can originate, amongst others, from sea salt spray, rising damp, road salt, salt storage and the building materials itself.