A dynamic response of structures determine its dynamic characteristics, i.e. the natural frequency, the corresponding figures of vibration and damping coefficient. Designing of a building in terms of dynamics lets us interfere in its stiffness and mass which allows the derivation of the structure of the resonance zone early in the design stage. It is known that the larger the value of the natural frequency the greater the stiffness of the whole structure. The article examined how the natural frequencies of the objectchange under the influence of adjustments in the development of the floor model. The main purpose of the analysis carried out in the article was to determine the relationship between stiffness and mass matrices and the results of the modal analysis of the chosen structure. The article hypothesized that the natural frequency is inversely proportional to the mass of the floor raised to a suitable exponent. A formula derived from this relationship has been verified on a number of variants of the building model made in the program for numerical calculation Dlubal.