The successful diagnostic activity has an important role in the changes of the repair costs and the efficient elimination of the damages. The aim of the general building diagnostics is to determine the various visible or instrumentally observable alterations, to qualify the constructions from the suitability and personal safety (accidence) points of view. Our diagnostic system is primarily based on a visual examination on the spot, its method is suitable for the examination of almost all important structures and structure changes of the buildings. During the operation of the diagnostic system a large number of data-valuable for the professional practice-was collected and will be collected also in the future, the analysis of which data set is specially suitable for revaluing construction and the practical application of the experiences later during the building maintenance and reconstruction work. For using the system a so-called "morphological box" has been created, that contains the hierarchic system of constructions, which is connected with the construction components' thesaurus appointed by the correct structure codes of these constructions' place in the hierarchy. The thesaurus was not only necessary because of the easy surveillance of the system, but to exclude the usage of structure-name synonyms in the interest of unified handling. The analysis of which data set is specially suitable for revaluing earlier built constructions and can help to create knowledge based new constructions for the future. © 2010, IGI Global.