Metal panels are unforgiving about what sits underneath them. A shingle roof can hide a soft patch of sheathing for years; a standing seam or exposed-fastener panel telegraphs it as a shadow, a dip, or a run of screws that won't stay tight. If you're on this page, you've probably seen one of those: a wave in the panel line that catches the afternoon light, screws backing out in the same area every season, a stain spreading on the attic side of the sheathing, or a spot on the roof that feels spongy underfoot. Daylight visible through the deck from inside the attic is the end-stage version. All of those point at the decking — the plywood, OSB, or board sheathing the panels are fastened into — rather than the metal itself.
Nobody can tell you the true extent of decking damage from the ground, and anyone who quotes a firm all-in number before the panels come off is guessing. What a proper look involves is getting into the attic first to read the underside — water tracking, rust staining around old fasteners, delaminated plywood plies, mold lines that show where moisture has been sitting — and then pulling panels and underlayment in the suspect area and probing the wood with an awl. Rot spreads along the grain and follows the water path, so the bad area is almost always larger than the stain suggests, and it usually runs downhill from a failed valley, a pipe boot, or chimney flashing. In central Ohio the other common source is winter condensation: warm moist air from the house hitting cold sheathing in an under-ventilated attic, which rots decking from the inside out across a wide area rather than at one leak point. Ice damming at the eaves does the same thing at the lower courses. If your attic has blocked soffit vents or no ridge path, expect the decking conversation to include ventilation, because replacing wood without fixing the cause buys you a few years at best.
Roof decking repair means cutting out the compromised sheathing back to sound wood, squaring the cut on rafter or truss centers so the new material has something to land on, and replacing it with the same thickness as what's there. That last part matters more under metal than under anything else — a 7/16" patch set next to 5/8" sheathing leaves a step that will show as a line in the panel for the life of the roof. Where the rafter tops themselves have gone soft, they get sistered before any decking goes down. Full roof decking replacement is a different job: it's what you're looking at when rot is general rather than local, when the sheathing is old plank decking with wide gaps that won't hold fasteners reliably, or when you're converting to a system that needs continuous support. Older homes around Columbus often have 1x6 or 1x8 board decking, and while that can be perfectly sound, a standing seam system with clips, or any panel needing consistent screw withdrawal, usually wants plywood laid over it or in place of it. Either way, the sequence is the same once the wood is right: ice-and-water membrane at eaves and valleys, underlayment across the field, then panels. Exposed-fastener panels rarely come off and go back without new fastener holes; standing seam panels often can't be salvaged at all, so decking work frequently turns into partial or full panel replacement.
Cost tracks sheet count, access, pitch, and whether the metal above can be reused. Steep roofs, second- and third-story work, cut-up rooflines with multiple valleys, and historic homes where matching plank decking is part of the job all add labor. Before signing anything, ask for a per-sheet unit price for decking found bad after tear-off, in writing, so you're not negotiating on a Tuesday afternoon with your roof open. Ask what thickness and material they're installing, how the roof gets dried in overnight, whether a permit is being pulled, and whether ventilation is being addressed or deliberately left alone.
Capital Ridge Roof Systems is licensed and insured, works across Columbus, Upper Arlington, Gahanna, and Dublin, and is reachable Monday through Friday, 8AM to 6PM. Financing is available, and several payment methods are accepted, which is worth knowing on a job where the final scope isn't fully known until the panels are off.