This thesis presents the designing of the administrative building of CGP according to the current Eurocode standards in the field of constructions. Reinforced concrete construction consists of two parts which are separated with dilatation. The focus is on the part of the building that was built in 2007 and consists of the basement, the ground floor, two floors and the attic. The load-bearing construction of this five-storey building consists of monolith reinforced concrete plates and walls of reinforced concrete which are connected with beams. The analysis of vertical load-bearing elements was made with the use of the ETABS program, while the analysis of ceiling plates was performed with the SAFE program. In the analysis, permanent impacts, impacts of imposed loads, snow and wind loads, but also seismic effects were taken into consideration. Presented in detail is the designing of characteristic ceiling construction, the most loaded cantilever wall, and the wall and the beam from the system of connected walls. The presented vertical load-bearing elements are designed by the method of capacity design. The purpose of analysing an already built structure is to compare the quantity of reinforcement required by Eurocode standards with the actual reinforcement, established in accordance with the requirements of the Yugoslav regulations (JUS). The comparison indicated that a more accurate model used in this thesis has a greater effect on the quantity of reinforcement in ceiling construction than the difference in regulations. Nevertheless, the Eurocode standard requires longer boundary elements and significantly less reinforcement in the web of the wall. In beams that connect the walls, there are small differences between the quantities of built-in reinforcement and the reinforcement required by the Eurocode standard. Shear reinforcement is sufficient, only the distance between the bars is too big. The amounts and locations of reinforcement in analysed elements are shown in the reinforcement drawing.