I am working with my plans examiner on a second story covered deck and am down to one issue to reconcile – rafter spacing. From IRC table R803.1, thickness of roof sheathing, rafter spacing can exceed the standard 24″ with 1-1/2″ T&G, however, there does not seem to be a corresponding table of rafter spans for spacing greater than 24″ per R802.4.1, rafter spans. My rafter span will be 9′ and am looking to space 4×6’s at 40″. While the plans examiner agrees that design is more than equivalent to 2×6’s at 24″ spacing, it is outside R802.4.1. Does anyone know of a referenced standard for rafter spans spaced greater than 24″?

Thank you,
Jeff