In this paper, numerical optimisation of aluminium prefabricated halls is made considering different wind and snow load zones in the Republic of Croatia. The main structural system is a portal frame with a tension-tie element. Standard frame spans of 10 to 20 meters and heights of 3 to 6 meters were analysed. Beams and columns were made of EN AW-6005 A aluminium alloy using extruded rectangular profiles 230 x 90 x 3 mm with slots. In the joint zones, aluminium profiles were connected using 180 x 80 mm tubular steel knee inserts with thicknesses varying from 3 to 6 mm made of structural steel S 235 or S 355. Parametric analyses were performed to find the optimal geometry of steel inserts in terms of uniform utilisation of aluminium and steel cross-sections for all considered frame geometries and load zones. Also, the material consumption is discussed. Based on the performed analyses, the preliminary geometry of the frame with their maximum allowable distances is proposed. These results can be used for cost estimations of the optimal disposition of aluminium halls in the Republic of Croatia.