Information on the structure formation of a lime-based finishing compound with polysaccharide additives is presented. It has been established that when polysaccharide additives are introduced into the lime mixture due to their adsorption on the surface of lime particles, the growth rate of the particle size of portlandite crystals slows down. There is a slight increase in the width of CaCO3 peaks, which indicates the possible incorporation of organic molecules into calcite. A change in the parameters of the crystal lattice in samples, especially those prepared with lime slaked in the presence of polysaccharides, has been established. Samples of calcareous stone based on lime slaked in the presence of polysaccharides demonstrate higher crystal lattice parameters compared with calcite of the control composition. A structure with inter- and intracrystalline organic substances is formed. Lime coatings with the addition of polysaccharides are characterized by higher cohesive strength, the frost resistance grade is F35. The values of the free energy of the coating surface are calculated.