OCFA Vertical Ventilation Practice Exam

In light weight panelized roof configurations, the spacing of structural members is chosen to balance load support with keeping the roof light and economical. Ceilings joists are typically spaced about 24 inches on center to provide a solid ceiling frame without adding unnecessary weight. Purlins are spaced around 8 feet apart to give intermediate support to the roof panels and prevent sag or distortion of the deck. The main beams, which carry the load from the purlins and roof panels to the walls or columns, are usually spaced much farther apart—often between 12 and 40 feet apart—so the system remains efficiently light and cost-effective.

The statement that is not true is the one claiming beams are spaced 8 feet on center. Spacing beams every 8 feet would require many more beams, increasing both the weight and complexity of the roof structure, which isn’t how typical light weight panelized roofs are designed. The broader beam spacing, such as 12'-40' apart, aligns with standard practice for these configurations.