There is an obviously increasing importance for assessing the moisture behaviour of building elements, especially in connection with questions concerning the rehabilitation of constructions and the elevated requirements for thermal insulation in future. On an European basis and within the frame of CEN there are efforts going on for using calculative methods in this field in an intensified way, to improve them and prepare new procedures for standardisation. Recently extensive investigations have been carried out in the Fraunhofer Institute of Building Physics for the experimental determination of necessary material properties as well as for the development of improved calculative methods. There are new findings for a physically correct description of moisture transport processes, tested measuring procedures and advanced programs for the calculative moisture assessment of building constructions. The contribution explains basic reflections including measuring examples and points out important consequences under practical aspects. Two one-dimensional examples - the annual moisture variance of an exposed natural stone facade and the comparison of the moisture behaviour of a brick masonry with and without the application of water repellent agent -are shown as well as one two-dimensional example which demonstrates the influence of a mortar joint.