In contrary to recently built office and commercial buildings, the service life of the traditional European residential houses was not calculated. Some estimations exist about the life span of different types of building constructions, however, these estimations may not reassure the owners of urban-type residential houses that were built before the second world war. A thorough and professional renovation may extend the service life of buildings by decades, the question is how to prepare the most effective renovation procedure.As a combination of the fuzzy signature structure and the principles of finite-state machine a new formal method is proposed for generating a tool for supporting the renovation planning, concerning the costs and importance of repair. With the support of information obtained from a given pre-war urban-type residential house, the available technical guides and the contractors’ billing database an optimized renovation process of the roof structure is presented as a case study.