Based on the stages of the construction period of the life cycle of the building, the authors examined the influence of gradual inclusion in the work, including the editing process, its individual building elements on the stress-strain state of a building and its individual design. Determined the nuances of the existence of the building (a separate structure), which should be taken into account at the design stage. These nuances are present in the real structure, but cannot be determined for calculations in the classical way (without changing the stress-strain state in process of erection and loading). Conducted numerical studies of the stress-strain state of a flat frame made from collapsiblemonolithic reinforced concrete with account of the phased construction. Also fulfilled a comparative analysis of the obtained results with data of calculation of the same frame, but not taking into account phasing of construction of the structure.