The article deals with the influence of karst processes on the deflected mode of the base plate. The urgency is because of frequent cases of accidents on the facilities constructed in the karst areas due to incorrect calculation of the effect of karsts on the bearing capacity of the building. The basic models of calculation of the soil bases and structures on stress and precipitation are described. The problems of determining the location of karst dips are discussed as well as the method of determining the estimated diameter of karst, depending on the category of it. The process of entering the boundary conditions for the Foundation slab on the bilinear basis model using satellite "Cross" is shown. The article also shows how module "Variation patterns" in SCAD Office for the multivariate location of karst dips can be used. The calculation of deflected mode of the Foundation slab without and with the account of karst is processed. Based on the obtained data, a comparative analysis of deflected mode according to the criterion of the required diameter of the karst is held. The conclusion is about effects of karst processes on the deflected mode of the base slab and the demand for their proper tasks.