When arranging a deformation monitoring system for a building, it is important to control the deformation state of its foundations. Various methods to control the deformation state of a building foundation include the method of hydrostatic leveling, which has a number of advantages. The article shows that this method, though underused now, is best applied to monitor differential foundation settlements on a continuous basis. This paper examines the factors affecting the accuracy of measurement by hydrostatic leveling and gives the recommendations for enhancing it. It was established that if measurements are made inside the building, it is possible to provide the level of measurement accuracy sufficient for most typical structures. The paper also gives examples of practical implementation of the self-engineered monitoring system based on the method of hydrostatic leveling, as well as their operating results.