The new method of the reliability calculation of buildings and structures’ earth foundations based on limited statistical information on controlled parameters in the operation stage is considered. The reliability is calculated by criterion of foundation deformations (settlement) in the presence of load eccentricity of the foundation and using possibility distribution functions for the description of fuzzy variables. New approach to the reliability calculation of a foundation bed is offered with describing eccentricity characteristic as random variable by the probability distribution law and properties of soil – by the possibility characteristic. The way for determination of eccentricity value of load on the foundation bed by measurement of deformations in the foundation material at the expense of unloading the part of the foundation on the area with resistance strain gages is considered. Reliability as the probability of failurefree operation of the foundation is characterized by the interval with minimum and maximum values.