How do you repair a leaking metal roof?
Short answer. Most metal roof leaks come from fasteners, panel laps, trim or penetrations, so the repair usually means replacing worn screws with new gasketed screws, often one size larger, resealing laps with butyl tape, refitting trim and closures, and replacing pipe boots. Use sealants rated for metal and compatible with your panel coating; general purpose caulk over dirty metal does not last.
Find it first
On exposed fastener roofs, check screw by screw along the line of the leak. Rubber washers dry out and crack in the sun, screws back out as panels expand and contract, and overdriven screws crush their washers. Then check end laps, side laps, the ridge cap, sidewall trim and every pipe or vent.
Repairs by source
- Fasteners: replace with new screws that have EPDM washers. If the hole is wallowed out, go up one screw size so the threads bite fresh material. Drive them snug, not crushed.
- Laps: separate the lap if possible, clean it, reseal with butyl tape sealant, and refasten. A bead of caulk over the outside of a lap fails quickly.
- Trim and ridge: replace missing foam closures, reseat loose trim, and seal with a metal compatible sealant.
- Penetrations: replace cracked boots with flexible square base boots made for metal roofs, set in butyl and screwed on a tight pattern.
- Rust holes: small spots can be wire brushed, primed and covered with a metal patch set in sealant and screwed down; widespread rust means replacing panels.
Coatings are a project, not a patch
Elastomeric and silicone coating systems can extend an aging exposed fastener roof, but only after rust, loose screws and open laps are fixed first. Painting over problems just hides them for a season.
Also read metal roofing in Georgia and common leak causes.