This article examines the justification for using one-dimensional structural models in the analysis of the thermo-stressed state in massive concrete and reinforced concrete structures during the building period. The paper presents calculation results for the thermo-stressed state in massive foundation slabs with different planform dimension ratios. Special attention is paid to presence/absence of thermal insulation on the sides of the slab during the mixture pouring process. Generally, onedimensional structural model is suitable in cases when ratio h/l < 0.17, h stands for the minimal plane dimension in a construction such as slab. The research indicates the existence of zones near the sides of slabs, where values of the tensile stress exceed the values that were obtained with use of onedimensional structural model. This excess may account for 9.5 %.