The penetration of moisture into the capillary-porous structure of concrete leads to the development of corrosion processes, the formation of efflorescence, the decrease in strength and the subsequent destruction of the cement-sand composite. At the same time, the increased humidity of the structure is a favorable environment for the development of various biological damages (mold, fungi, lichens), which, in turn, leads to both decrease in the operational characteristics of the structure and loss of the aesthetic appearance of the building facade. In this regard, the study of possibility of increasing the waterproofing of concrete by compaction of its structure is of great interest. The paper discusses the effect of penetrating additives on the physicomechanical characteristics of fine-grained concrete and fiber-reinforced concrete. It has been established that the introduction of a penetrating additive into the composition of cement-sand composites leads to the filling of the capillary-porous structure of materials with needle-like new formations, which makes it possible to increase their resistance to moisture influence, namely, to increase the waterproof grade, reduce the depth of water penetration into the concrete structure, increase the contact angle of wetting the surface of the material. It was also noted that the simultaneous introduction of a penetrating additive and fiber into the concrete composition allows not only to increase the waterproofness of the composite, but also to improve hydrophobic performance by imparting a hierarchical surface structure to the material.