In single storey industrial buildings, the most common material used for the load-bearingsystem is steel. The load bearing system can be designed in different ways. The two mostcommon load-bearing systems of steel industrial buildings are portal frame and thetruss/pillar-system. The benefit of using these systems is the possibility of having largespan structures. These systems have also a high load capacity in function of its weight.Geometrical parameters like width, height, length, and roof slope of the building effectsthe design and the selection of which load-bearing system will be more suitable.The purpose of this thesis is to compare the two systems in terms of weight of steel, priceand global warming potential (GWP) and to see how the load-bearing systems differ. Tofulfil the purpose, it is necessary to find the geometrical parameters to design an optimalportal frame system and use the same parameters in order to design the truss/pillarsystem. By using the same geometrical parameters, the two systems can be comparable.The results of this thesis show that the truss/pillar system has less weight, lower price andlower global warming potential than the portal frame.As conclusions of this parametrical study, it was seen that the truss/pillar system isperforming better than the portal frame system. In general, it is not possible to say that thetruss/pillar-system is better. This is because this thesis work did not consider amongstithers the bracing system, foundation, connections, mounting or fabrication. But it ispossible to say that the differences between the two systems are not major.