For the calculation of foundation settlement it is recommended to take into account so called influence zone inside the subsoil bellow the carrying structure. Influence zone inside the subsoil is the region where the load has a substantial influence on the deformation of the soil skeleton. The soil skeleton is pre-consolidated or over consolidated due to the original geostatic stress state. An excavation changes the original geostatic stress state and it gives the space for loads passed from upper structure. The theory of layered subsoil in Westergard manner is selected for the vertical stress calculation. The depth of influence zone is calculated from the condition, that the original geostatic stress is equal to the new geostatic stress due to excavation plus the vertical stress influenced by the surcharge of upper structure. The way, how to estimate the depth of influence zone, is expressed in the graphs.