In the practice of modern construction, light concretes of low thermal conductivity are used as a thermal insulation layer of enclosing structures. In particular, they are used for insulation of flat roofs of buildings for various purposes. One of their effective methods of thermal insulation is the use of polystyrene concrete of low average density and thermal conductivity directly in building conditions. Studies have established the rational selection of the composition of this type of concrete for the device of a monolithic thermal insulation layer, the resource support of the technological process, including the mechanization of work and qualification requirements for performers. The improvement of organizational and technological solutions of flat roofs based on the choice of rational parameters of technological processes and operations ensures a reduction in the complexity, duration and cost of work on the construction site.