Galvalume Gutters: Strength, Lifespan and What to Avoid
Updated · By the Roof to Footing editors
Galvalume gutters are steel gutters with a coating that's about 55% aluminum, 43% zinc and a little silicon. The coating protects the steel better than plain zinc galvanizing in most climates, so Galvalume gutters resist rust longer than galvanized ones while staying much stiffer than aluminum. They're a common choice under metal roofs and in snow country, and they cost far less than copper.
Galvalume is a registered trademark, but people use the name for any steel with that aluminum-zinc coating, sometimes sold as AZ50 or AZ55 after the coating weight.
How it compares
| Galvalume steel | Galvanized steel | Aluminum | |
|---|---|---|---|
| Coating | Aluminum-zinc alloy | Zinc | None needed; aluminum doesn't rust |
| Stiffness | High | High | Lower; dents easily |
| Snow and ladder resistance | Good | Good | Fair |
| Rust at cut edges and scratches | Some edge staining, slow | Rusts sooner once zinc is gone | No rust |
| Weight | Heavy | Heavy | Light |
| Typical finish | Bare silver or painted | Bare or painted | Painted |
Compared with galvanized steel gutters, the aluminum in the coating forms a barrier that holds up longer in most rain and atmospheric conditions. Compared with aluminum gutters, Galvalume shrugs off ladders, falling branches and ice that would kink a thin aluminum gutter.
What damages Galvalume
The coating is tough, but a few things attack it:
- Wet concrete, mortar and stucco. The alkalinity eats the aluminum in the coating. Keep the gutter and downspouts off fresh masonry and don't let mortar splash on them.
- Copper runoff. Water that runs off copper (a copper roof, copper flashing or copper chimney cap) carries copper ions that corrode Galvalume. Don't put Galvalume gutters under copper.
- Pressure-treated lumber. Modern treated wood is corrosive to the coating where they touch. Use a barrier or keep them apart.
- Lead. Lead flashing in contact with Galvalume causes corrosion.
- Abrasive cleaning. Wire brushes and harsh cleaners strip the coating.
Bare or painted
Bare Galvalume has a spangled silver finish that dulls to a soft gray. Painted Galvalume (usually a Kynar 500/PVDF or SMP paint system) comes in the same colors as metal roofing, which is why roofers often match gutters to the panels. Paint adds protection, but touch up scratches so they don't start edge creep.
When Galvalume is the right pick
- Under a Galvalume or painted steel roof, where the gutters can match the panels.
- In heavy snow areas, where aluminum gutters bend or pull loose.
- On barns, shops and outbuildings, where strength matters more than looks.
Skip it in coastal salt spray zones close to the water. There, aluminum or copper usually holds up better, and the extra stiffness of steel doesn't make up for faster corrosion. For a matching roof, see our guide to the Galvalume roof.