The results of studies on the use of the impact echo method for thickness gaging of compact concrete building structures are presented. It is shown that in compact building structures, in which the thickness being measured is comparable with other sizes of the test object, it is impossible to determine the sought-for thickness of the product based on its own resonant frequency due to the geometric dispersion of speed of sound. The influence of geometric dispersion is different for each compact product, and, as a result, it is necessary to measure the correction factor of the geometric dispersion of speed of sound individually for each compact product. A technique is proposed for determining the factor in compact products that ensures both the determination of the fundamental resonance frequency and the elimination of the influence of the geometric dispersion of speed of sound on the accuracy of thickness gaging of compact objects.