The book is based on the rich experience of Leningrad architects and restorers. It is told about the technical and planning features of pre-revolutionary houses, their technical expertise, restoration and the possibility of further use. Methods of objective diagnostics, the procedure for determining physical wear of buildings during technical inventory of fixed assets, the current methodology for determining moral wear during revaluation of fixed assets are described. Methods for determining the maintainability of old buildings and recognizing construction defects in them are indicated. The book summarizes the long-term experience of Leningrad specialists.