Coastal is different
Palm Beach County's east side lives in salt air. Every surface outdoors gets a film of salt on it that is refreshed by every onshore wind and only rinsed by rain. On a metal roof, salt plus moisture plus time is the recipe for corrosion, and the maintenance of a coastal metal roof is mostly about denying that recipe one of its ingredients.
Where it starts
- Cut edges. A coated panel is protected on its faces. Where it was cut to length, the raw metal is exposed. Edge creep - rust working in from a cut edge - is the classic coastal failure.
- Scratches. Anything that broke the coating: a dropped tool, dragged equipment, a branch. Small, but a starting point.
- Fastener heads and the washers under them.
- Dissimilar metals. A copper wire or a lead pipe flashing running onto a galvanised or aluminium panel will corrode the panel where they touch and where water runs from one to the other. So will steel screws in an aluminium roof.
- Anywhere water sits. Behind a chimney, in a low panel, under debris - anywhere salt-laden water stays instead of running off.
What rinsing does
Rain is a rinse, and a metal roof that gets regular rain on every surface usually looks after itself. Sheltered areas - under eaves, behind parapets, under solar panels - do not get rinsed, and those are where salt accumulates. A low-pressure fresh-water rinse of those areas is legitimate maintenance. Pressure washing is not; it is how coatings get damaged.
What to look for
Any rust staining, especially in a line below a fastener or at a panel end. White, powdery corrosion on aluminium. Coating that has gone chalky or is peeling. Any place where two different metals touch.
What good looks like
A coastal metal roof that was specified for the coast - the right alloy or coating, matching fasteners, no dissimilar-metal contacts - and looked at every year will last a very long time. The same roof with a steel screw in the wrong place and a branch scratch that nobody saw will develop a hole in a few years at exactly that spot. The difference is the looking.
Coastal metal roofs get a specific check on every visit: edges, fasteners, dissimilar-metal contacts and the sheltered spots that rain does not reach.
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