Assessing the condition of old masonry structures is a demanding task with several unknowns. In this paper, the mechanical properties of the masonry walls and the dynamic parameters of the structure are evaluated for the masonry structure damaged by the earthquake. In the introduction, an overview of load-bearing masonry standards and examples of experimental testing of mechanical properties of masonry in the laboratory and in situ are presented. Afterwards, the building is visually inspected and an experimental investigation of the material properties is performed. The damage determined by visual inspection was confirmed by the control of the basic requirements for load-bearing walls. Based on the obtained results of the mechanical properties of the masonry during the experimental investigation and the recommended values from the literature, a numerical submodel of the characteristic load-bearing wall was made. The numerical submodel, which was also used for the initial global numerical model, describes the tests that have been performed. Obtained results are very similar to those experimentally determined. However, the initial global numerical model shows the uncertainty of the experimental results. In order, to correspondence the results of the actual behavior of the structure and the numerical model, considering the dynamic parameters of the structure, a whole series of iterations were performed. The following iterations are included: changes in boundary conditions, modeling of partition walls, modeling of damages, and changes in global stiffness of the structure. Compared to the initial numerical model, changing the boundary conditions on the numerical model did not result in significant differences in the natural frequencies of the structure. Afterwards, a comparison of the numerical model with modeled partition walls and the numerical model with the entered mass of partition walls was performed. The result was a higher frequency in models with modeled partition walls due to the increase in structural stiffness. Following iterations included the introduction of structural damage into the numerical model. Damage was initially modeled by reducing the modulus of elasticity of finite elements that belong to the damaged parts of the building. The results of the natural frequency of the structure were not satisfactory. Afterwards, according to the recommendations from the literature, the damage was modeled by reducing the modulus of elasticity of finite elements along the cracks. The global stiffness of the structure of the model with a reduced modulus of elasticity of finite elements along the cracks, is ultimately altered. The global stiffness of the structure directly affects the natural frequency value of the structure. Based on the above assumptions that were introduced into the global numerical model, very good results were achieved between the numerical model and the actual behavior of the structure. Therefore the global numerical model can be considered beneficial for future assessment and reconstruction project.