Pole buildings use purlins, not rafters for main roof boards. Purlins are installed horizontally. Rafters are installed vertically from peak to eve.
- Purlins are sized according to snow load of specific location.
- Commonly 2×6’s are used at 24” on-center with posts set at 12’ apart.
- If posts are spaced further apart or snow load is greater than 25lb., the size of purlin could increase and or spacing could decrease.
- Buildings are specifically designed for each location.
- Purlins are commonly installed on top of trusses but can be installed to side of top cord of truss with a hanger.