This addition to the GeoSure ground stability data consists of a single data layer in Geographical Information System (GIS) format that identifies areas of potential shrink-swell hazard at subcrop level (up to 10 metres depth) in Great Britain. It is essentially a national hazard susceptibility map. This data has been produced by geologists, geotechnical specialists and information developers at the British Geological Survey and is presented as a GIS data layer. Swelling clays can change volume due to variation in moisture, this can cause ground movement, particularly in the upper two metres of the ground that may affect many foundations. Ground moisture variations may be related to a number of factors, including weather variations, vegetation effects (particularly growth or removal of trees) and the activities of people. Such changes can affect building foundations, pipes or services.