Abstract: Following article represents the publication of the results of the study carried out by NIiPI Spetsrestavratsiya as part of the preparation of the unified protection zones project for cultural heritage properties located on the territory of Saint Petersburg. The object of the study was the ordinary buildings created before 1957 (mainly in the historically formed central districts of Saint Petersburg), their particularities, which can be considered as a basis for detailing the existing requirements aimed at preserving the architectural and urban environment of St. Petersburg and maintaining its integrity. Ordinary buildings were considered as a sum of historically interconnected elements, united by structural, functional, historical and cultural relationships. In the course of the study, a system of categories was proposed, which was determined both by the state of individual buildings and their role in the urban environment, and by the importance of the environment itself as an independent object of protection. The six categories of buildings identified during the work differ by their historical (including memorial), architectural and urban significance. When assessing the urban environment, the state of conservation the environment itself was taken into account (historical blocks frontage lines, historical parcellation plan, volumetric and spatial parameters of the development, type of organization of the street front and inner-block spaces, historical landscaping), as well as the compliance of each of the analyzed buildings with historical urban environment characteristics. Thus, the analysis was carried out from the point of view of the value, integrity and authenticity of each building and from the point of view of its participation in maintaining the valuable qualities of the environment. As a result of the study a summary list of more than nine thousand valuable buildings, forming historical urban fabric of Saint Petersburg, and its graphic equivalent in GIS format were drawn up.