Damages on building stones caused by weathering were studied by new methods of investigation. The Institute of Soil Science and Engineering Geology (Institut für Bodenforschung und Baugeologie), University of Agriculture Vienna, is involved in this interdisciplinary research together with other relevant scientific institutes. The main effort of this project is concentrated on the research of biological weathering and it is based on the important mineralogical and petrological studies of A. Kieslinger. The density and the species of colonisation by microorganisms are investigated by modern methods and biological signs of life of microorganisms which are the cause of biological weathering are inquired. Improved measures against the stronger influences of weathering in the last decenniums should be drawn from the results of these investigations.