The paper reveals the mechanism of cracking in the "aerated concrete masonry - plaster coating" system, which causes the reduction of cladding’s durability. The temperature deformations in the structure are analyzed. On this basis the theoretical background to optimize the composition and technological parameters of the plaster was developed. The composition of plaster mixtures based on the expanded clay, carbonate, perlite and other fillers was also developed. The proposition that targeted modification of plaster can ensure optimal operation of the "layingplaster" system is experimentally confirmed.