The article is devoted to the actual problem of disruption of the normal temperature and humidity conditions in the basements of the old building stock in St. Petersburg. The article considers the main causes of disruption of the normal temperature and humidity conditions and its impact on the building construction of the residential units. The following defects and damages of structures in basements of old building stock are analysed: violation or lack of due system of ventilation, violation or lack of waterproofing the basements, formation of cracks in the base body, malfunctioning of drainage system, the increase of ground waters level, leakages of external and internal sanitary networks. We also consider the negative consequences of violation of normal temperature and humidity conditions of basements, namely chemical, physical and biological damages, which can lead to destruction of building constructions; as well as the change of physicomechanical characteristics of soil in the bases of foundations. It was concluded that the overwhelming number of injuries leading to disruption of temperature and humidity of basements occur during their operation. It was also pointed to the economic feasibility of the use of basements after restoring normal operating conditions in the central historical part of St. Petersburg.