Metal Roofing Materials: Steel, Aluminum, Copper, and Zinc

"Metal roof" tells you the shape of the thing and nothing about what it is made of. The material decides how the roof corrodes, how it moves, what it costs, and where it belongs. Here is what the residential options actually are, and which one we put on houses in the inland Midwest.

Steel

Almost every residential metal roof in Indiana, Ohio, and Michigan is steel, and there are good reasons. It is strong for its thickness, it holds a flat panel without waving as much as softer metals, it takes a factory paint finish well, and it is the most affordable of the durable options.

Bare steel rusts, so roofing steel is coated at the mill before it is ever painted. Galvanized steel carries a zinc coating. Galvalume carries an aluminum-zinc alloy coating, and it is the standard substrate for painted residential roofing because it resists corrosion longer than plain galvanizing in most exposures. The paint goes on top of that. Our panels are Galvalume steel, coated at the mill with either AkzoNobel Ceram-A-Star 1050 or Sherwin-Williams WeatherXL. The coatings page covers the paint side.

Gauge is thickness, and a lower number is thicker. Residential standing seam is commonly 24 gauge; cheaper exposed-fastener panels are often 26 or 29. Thinner steel is more prone to oil canning, dents more easily in hail, and relies more on the rib profile for stiffness. When comparing quotes, ask the gauge. A price that looks low is sometimes a thinner panel.

Aluminum

Aluminum does not rust. It forms its own oxide layer and stops. That makes it the right material anywhere salt is in the air, and for a coastal home I would tell you to insist on it. We do not write for those markets.

Inland, aluminum is a tradeoff. It is lighter and softer than steel, so it dents more easily and moves more with temperature, and it costs more. Galvalume steel with a good finish handles Midwest weather without aluminum's downsides, which is why it is what we install here.

Copper

Copper is beautiful, it lasts a century, it develops a patina, and it is expensive enough that it is usually an accent, a bay window roof or a porch, rather than a whole house. It also sets up galvanic corrosion with steel, so copper flashing on a steel roof, or copper gutters draining onto steel, is a mistake. If you want copper, it is its own project.

Zinc

Zinc is a self-healing, long-lived material common in Europe and rare here. It needs a specific assembly with ventilation behind it, installers who know it, and a budget near copper's. I mention it so you know what it is when you see it. It is not a practical choice for most Midwest homes.

Stone-coated steel and the rest

Stone-coated panels are steel underneath, with granules bonded to the surface for texture. The material question is the same as any steel roof; the difference is the profile and how it handles water, which is covered in the three-system comparison. "Tin roof" is a nickname for an old terne-coated steel roof, and nobody installs tin.

Mixing metals

This is the rule that bites people. Two different metals in contact with moisture corrode each other, and the less noble one loses. Copper against steel, plain steel screws into aluminum, treated lumber against any panel. Every flashing, fastener, and trim piece should be matched to the panel. A contractor who does this every day does it without thinking. One who does not is how a good roof gets a rust line down one side.

What I would tell you

For a house in our service area, the material decision is mostly made for you: Galvalume steel, a factory coil coating you can look up by name, a gauge you have asked about, and hardware that matches. The decision that actually changes your outcome is the system, how the seam is formed and where the fasteners are, not the metal. If someone is selling you on an exotic material for a house in Fort Wayne or Noblesville, ask what problem it solves that steel does not.

If you are on the coast, the answer is aluminum and it is not a close call. If you want copper for the look, understand you are buying a different roof at a different price.

Now you have the context to know what the metal in "metal roof" should be.