Repair or Replace?

Diagnose by symptom, not by age alone

• Backed-out fasteners (exposed-fastener roofs): the classic 10–15 year service item. Thermal cycling works screws loose and gaskets age. Fix: systematic re-screw with oversized, new-gasket fasteners. A maintenance job, not a roof replacement.
• Leaks at penetrations: vents, chimneys and skylights fail at their flashing long before panels fail. Re-flash the detail; don't let anyone quote you a roof for a boot problem.
• Surface rust at cut edges or scratches: spot-treat early (clean, converter, touch-up system matched to the coating). Widespread red rust on old galvanized barn steel is different. That roof is telling you its zinc is spent.
• Oil-canning (waviness in flat panel areas): visual, not functional. It doesn't leak and isn't a defect claim in most warranties. Striations or thicker gauge prevent it at purchase time; nothing economically fixes it after.
• Storm dents: usually cosmetic on steel (see the insurance guide before filing).

The honest thresholds

Repair when damage is local, the panel profile is still made (matching matters), and the roof is under ~70%% of its service life. Replace when leaks are systemic rather than at details, when a discontinued profile makes patches impossible to match, when old galvanized coating is exhausted across slopes, or when you're already opening the roof for a solar or renovation project and the remaining life is under 15 years. And if you're replacing asphalt for the second time. Stop buying the same roof twice; run the 50-year comparator before you commit to a third.

Recover or tear off?

Steel's light weight (roughly a third of asphalt's) makes recover. Installing over one existing asphalt layer on strapping or approved underlayment. A code-permitted option in many jurisdictions. It saves tear-off cost and landfill, and the old roof becomes a secondary weather layer. It's the wrong choice when the deck is suspect (soft spots, past leaks), when two or more layers already exist, or when local code says no. A contractor who probes the deck and checks code before answering is the one to hire; our hiring checklist covers the rest.