Our office dealt with the structural assessment of an existing two-storey building with a basement due to the existence of certain structural irregularities. In the building there was provision for the addition of four new floors, but due to the above-mentioned structural irregularities it was deemed necessary to check the structure for their addition. The load-bearing body of the existing structure consists of reinforced concrete frames, beams-columns system, as the same applies to the newly built floors. For the adequacy check, an elastic dynamic analysis was performed, specifically the Response Time History Method (National Intervention Code, §5.6.3.3) with local factors m. The analysis and the adequacy check were carried out with the software FespaR 22 v.8.3.0.16 of the LH Software company.