This article deals with a safety problem of upkeep of buildings and structures, specifically soil reliability according to the strength criterion with absolutely limited information about pressure by building foundation on the ground. For solving the problem of pressure of foundation on the ground the new ways for calculating reliability and for the first time truncated distribution for description of random value were used. Calculated reliability of foundation is expressed as an interval of numeric values. Design equations for determination of upper and lower values of reliability in the interval, method of risk calculation are presented in the article. Solutions on the definite value of foundation reliability by the estimated range of reliability are applied.