As a general rule, most steel roofing panels can span up to 8ft to 12ft without additional structural support provided purlin spacing, gauge, and profile are correctly matched. Beyond 12ft, engineered framing becomes increasingly important. Beyond 20ft, a structural ridge beam or steel frame is typically required. The honest answer is that “maximum span” depends on too many variables to give a single number gauge, profile, snow load, and pitch all interact. When in doubt, call Metal Pro before you order.