Technical maintenance of existing buildings will be an important issue in the near future. The purpose of the research presented in this paper was to identify element deterioration in the course of maintaining residential apartments. In order to reach the research goal, the author analysed symptoms of the technical wear increase, i.e. performing the identification of mechanisms responsible the defect formation. The scope of this work required the creation of an original qualitative model for pinpointing defects and transferring this information into a quantitative one. Thus, it was possible to analyse the reason-effect phenomena ‘defect – technical wear’ relevant to the most important elements make an assessment of such an apartment block. The building in question is a block of apartment houses in Wrocław. The information gathered should prove indispensable for housing management and other such organisations involved with technical building services, as it can serve to influence the maintenance quality level of different types of existing buildings.