The article deals with the problems of restoration design and study of cultural heritage objects that have a long history of existence and operation since the first half of the 19th century. The main aspects faced by researchers of monuments in our time are listed. The list of problems that designers face when studying such objects in St. Petersburg is given. A small dive into the technology of historical development for 250-300 years in St. Petersburg is made. The features of historic masonry and reinforced masonry structures are discussed. In particular, the problems of the state of brickwork walls of cultural heritage monuments of the early 19th century are listed. As a result, it can be stated that the technical and technological difficulties of restoration and the most problematic objects in the design were left to the current generation. We can also say that the current community of restoration designers, to a greater extent, does not take into account many factors that affect the integrity and load-bearing capacity of masonry historical walls. Using the example of a cultural heritage object - the building of the mansion of A. A. Polovtsov, the stages of design of restoration work and analysis of the result obtained and forced corrections after detailed restoration implementation in the structure during its restoration and conservation are given.