Box girders with steel cantilevers are often used in the design of composite steel bridges. The welded joints between the main girder and the transverse system are exposed to fatigue loading. Manual welds are common for which the manufacturing conditions can vary in terms of welding position and environmental settings. It is therefore intended to quantify the effect of manufacturing conditions on the fatigue strength and its scatter. Constant amplitude (CA) fatigue tests on identically designed specimens with different manufacturing conditions were carried out to enable this review and to develop initial approaches for a new method that integrates information on manufacturing conditions into the design concept.