Side by side
How do Galvalume and galvanized metal roofs compare?
Galvalume usually wins on roofs because it lasts longer in the weather, but neither one is right for a home on salt water.
Galvalume and galvanized steel roofing compared
| Feature | Galvalume | Galvanized |
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| Coating | About 55% aluminum, 43.5% zinc, 1.5% silicon | Zinc |
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| Common weight names | AZ50 painted, AZ55 unpainted | G60, G90, G100 |
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| Florida Building Code minimum (2010 text) | AZ50, 0.013 inch steel | G-90, 0.013 inch steel |
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| Cut edges | Sheffield says the coating can slow red rust at cut edges | Sheffield says red rust spreads once steel is exposed |
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| Salt air | Sheffield says salt can degrade it, and warranties exclude near-coast homes | Sheffield says it degrades quicker near the coast |
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| Mill warranty | Often available against perforation | McElroy says similar warranties are not typically available |
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| Best fit | Most inland roofs and walls | Dry inland areas, and animal buildings where Galvalume is not advised |
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Sources for the table: McElroy Metal, Sheffield Metals and the Florida DBPR quote of the 2010 building code. Coating names are weights, in ounces per square foot of coating across both sides of the steel. McElroy says G100 holds about 66 percent more zinc than G60, and calls AZ50 the industry standard for painted panels and AZ55 the usual weight for unpainted ones.
What the code says. The 2010 Florida Building Code text quoted by DBPR lists aluminum-zinc steel panels at 0.013 inch minimum, with AZ 50 as the minimum coating rate, and galvanized panels at 0.013 inch with G-90 zinc. Real panels sit well above that thickness, and 26-gauge steel is nominally 0.0185 inch according to a Florida approval we reviewed. Check the current code edition with your building department.
Cut edges. Every roof panel gets cut somewhere, at ridges, valleys and walls. Sheffield says Galvalume's self-healing slows red rust at a cut edge, and that a little red rust there is normal and will eventually stop. It says galvanized does not self-heal, so red rust spreads once the steel shows. Sources disagree on the short term, and McElroy's own paint warranty excludes the formation of rust on panel edges, so treat cut edges as something to protect with proper trim and sealant either way.
Warranty. Sheffield says a typical Galvalume substrate warranty runs 15 to 25.5 years, and terms vary by maker. McElroy's paint warranty for painted Galvalume lists 50 years on the substrate and 40 years on paint adhesion, with exclusions. Sheffield adds that manufacturers often do not offer warranties on galvanized products at all.
