Can a missed rafter be treated as a deck-mounted solar attachment?

Not automatically. Missing a rafter does not by itself create a valid roof-deck connection. Deck mounting is possible when the selected attachment supports that method and the roof-deck substrate, specified fasteners, screw pattern and attachment spacing meet the manufacturer’s instructions and project-specific structural requirements. For example, IronRidge’s HUG manual gives separate rafter-attached and deck-attached procedures, with different screw arrangements and engineering requirements when changing methods. SnapNrack’s UltraFoot Deck data sheet likewise distinguishes roof-deck and wood-framing fastening conditions. Do not simply leave a rafter-mount screw in the sheathing or copy another product’s fastening details. Verify the proposed connection against the selected system’s installation and engineering documents; obtain manufacturer or structural-designer guidance before accepting a changed attachment detail.

Sources: IronRidge, QuickMount HUG Installation Manual, Rafter-Attached and Deck-Attached Installation: https://files.ironridge.com/pitched-roof-mounting/resources/brochures/IronRidge_QuickMount_HUG_Installation_Manual.pdf SnapNrack, UltraFoot Deck Technical Data Sheet, Rev. B (February 6, 2025): https://res.cloudinary.com/summitpoint/image/upload/v1742842287/SNR_DC_01437_SNAPNRACK_TDS_ULTRAFOOT_DECK_REV_B_250206_d7e6874e4c.pdf