Martin Thompson
On average, how much rust should I expect at the eave edge of my prepainted galvanized roof over a period of 20yrs under normal conditions? (not an animal confinement, not near salt water, rural location, 4:12 slope. 1/4", 3/4", 2" in??
Brian Selig
Architectural Building Components Metal Roof and Wall Panels
I'm not sure how extensively this has been measured. There is no limitation to this. Galvanized, prior to being painted, typically does not come with a warranty. Many manufacturers have moved away from Zinc galvanization on their steel to zinc-aluminum to extend the protection. In our standing seam systems, we hem the panels at the eave to hide them. There are studies available: search galvanized vs. galvalume.
Todd Miller
Isaiah Industries, Inc.
I really do not think there is anything verifiable in regards to this either. There are also so many variations in terms of grades of steel and coatings.
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