Where metal roof leaks usually start
Water finds the weak points, and on metal those are predictable. Before anyone talks about new panels, an installer should check these first.
Fasteners on ribbed panels
Ribbed (agricultural) panels are screwed through the face, and each screw seals with a rubber washer. Over years of hot days and cold nights the panels expand and contract, the screws work loose, and the washers dry out and crack. A screw that was driven crooked or too tight leaks from day one.
Lap seams on ribbed panels
Where one ribbed panel overlaps the next, a strip of sealant or butyl tape keeps water out. When it shrinks or the lap was short, wind-driven rain gets in. Standing seam panels rarely leak along the seam itself; trouble there tends to show up at panel ends, the ridge, or a seam that was bent.
Chimney, skylight and pipe flashing
Most chimney leaks on metal roofs come from flashing that was caulked instead of properly cut in, or from a chimney where the mortar has gone soft. Skylights need their own flashing kit, not a bead of sealant around the curb. Rubber pipe boots crack in the sun and are a simple, common fix.
Valleys
A valley carries water from two slopes, so a bad cut or missing ice and water barrier under it shows up fast, usually as a stain on a ceiling well below the valley.
Loose screws and backed-out fasteners
If you can see screw heads standing proud of the panel, or rust streaks running down from them, the fasteners need attention. The fix is a new screw with a fresh washer, often one size larger so it bites into a hole that has worn oversize. Doing every screw on an older barn or garage roof at once is normal and far cheaper than chasing leaks one at a time. If you have a metal barn roof with exposed fasteners, plan on this every so often.
Storm, ice and snow damage after an upstate winter
Wind lifts trim and ridge cap before it lifts panels, so loose edges are the first thing to check after a storm. Falling limbs dent and puncture panels, and a punctured panel usually needs replacing rather than patching.
Winter is harder on a roof than any single storm. Snow sliding off a metal roof can tear off gutters, shear plumbing vents and bend lower trim, which is why snow guards for metal roofs belong on the list for any repair above a door or a lower roof. Ice dams at cold eaves push water up under laps on low-pitch roofs. Up in Glens Falls and around Lake George, where the snow sits longer, these show up as spring leaks.
Sealant or a real metal roof repair
Caulk has its place, but a tube of sealant over a leak buys a season at best. Asphalt roof cement is worse: it traps water against the steel and hides what's going on. Here's how patches compare with proper fixes:
| Problem | Patch that buys time | Proper repair |
|---|---|---|
| Leaking screw | Sealant over the head | New screw and washer, upsized if the hole is stripped |
| Open lap seam | Caulk along the edge | Clean, new butyl tape or sealant, re-fasten |
| Chimney leak | Sealant at the joint | New step and counter flashing |
| Rusted-through spot | Patch plate | Replace the panel |
Watch for mixed metals too. Copper touching galvanized or galvalume steel, or the wrong screws, will corrode the panel around them.
Repair or replace your metal roof?
Repair it if the trouble is in one area: a few screws, one chimney, one valley, storm damage on one slope. Replace it when rust has eaten through panels in several places, the finish is chalking and flaking across the whole roof, or the roof has been patched so often nobody can tell where the next leak will come from. Older ribbed roofs on farmhouses and barns often land in between, where a full screw replacement and new flashing earn a lot more years.
If replacement makes more sense, the installer can price a new roof alongside the repair so you can compare. See metal roof installation for what that involves and the metal roof cost guide for what drives the price. We cover homes and outbuildings from Saratoga Springs to Glens Falls.