Abstract—The aim of the study was to assess the possibility of the use of formulations based on hydrophobic organosilicon compounds for the impregnation of porous building materials such as ceramic brick and natural stone - calcareous gaize. The process of the surface hydrophobization was analyzed. The study examined the effectiveness of two formulations differing in the degree of hydrolytic polycondensation, viscosity and concentration, as these are the factors that determine the final effect of hydrophobization. The following laboratory tests were performed: analysis of the physical characteristics of the tested materials, surface absorption, the analysis of characteristics and defects of silica gel nanofilm by using the SEM images.