This master thesis deals with the project of a single-nave and single-storey steel hall located in the area of the city of Zagreb. The project contains a dispositional solution, an analysis of actions and the design of structural elements and joints according to HRN EN. Also, detailed drawings of joints of the load-bearing structure were made. The layout dimensions of the hall are 40 m x 80 m, and the height of the ridge is 15 m. The main load-bearing system of the hall is a symmetrical portal frame. The roof is duopitch and the slope of the frame beam is 15°. In addition to the self-weight of the structure, all variable loads (snow, wind, and seismic action) were taken into account in accordance with the location of the building. For the entire hall, steel grade S355 was used. The development of models and the design of structural elements was conducted in the software 'SCIA Engineer' while the software 'Autodesk Robot Structural Analysis Professional' was used for the design of joints. Three variant solutions were considered, which differ in cross-sectional profiles used for the construction of beams and columns of the frame. In variant solution 1, beams and columns of the frame are hot-rolled profiles. In variant solution 2 beams and columns of the frame are welded profiles of uniform cross-section, while in variant solution 3 beams of the frame are welded profiles of uniform cross-section, and columns are welded profiles with tapered cross-section. Finally, variant solution 3 was chosen as the optimal solution based on the criterion of material consumption. The thesis also includes a comparison of the results of manual and computer design of welded beams and columns for the selected optimal solution. For tapered cross-section members, a deviation of results was observed, which is explained in detail in this thesis. It should be emphasized that the members with tapered cross-sections are almost uncovered by the norms for the design of steel structures and the design is based on the available literature.