Moisture detection in heritage buildings by 3D laser scanning

Moisture is one of the main factors in the deterioration of heritage buildings, causing mould, unwanted parasites, and the decanting of salts, which, in turn, aggravate such degradation. The existence of moisture not only affects the building aesthetically, but is also evidence of bad conservation conditions. It is thus extremely important to verify and assess the extent of the moisture, even though it may not be confirmed by mere visual inspection. This article describes an innovative and straightforward procedure to automatically show where moisture appears, as well as the affected area. The procedure is based on the use of 3D laser scanner surveying data for documentation purposes of historic buildings. Data are processed off-line in order to analyse the laser reflectivity level. The method is not intrusive, allows large areas to be covered in a short time, and does not interact with the materials, which makes it optimal for application to these special buildings. Hence, professionals of the conservation sector will have objective and comprehensive information on moisture damage, helping them to take decisions on the action to be undertaken. The results achieved in the Cathedral of Ciudad Rodrigo (Spain) are shown to demonstrate the utility of the proposed method.