We all know that metal rusts, and we also know that rust can weaken or destroy metal structures over time. Even a durable car – particularly in the north, with salt on the roads – will decay. Why shouldn’t the same be true for a metal roof? As it happens, manufacturers engineer metal roofing specifically to avoid rust, much longer than one might otherwise expect.
Metal roofing is resistant to most forms of decay. Being naturally waterproof, metal sheds rainwater quickly and does not develop mildew or mold. This is partially why metal roofs do not rust easily, as they are immune to many other forms of rot.
Keep in mind that roofers are well aware of the rust factor when it comes to metal roofs. That’s why manufacturers engineer metal roofing obsessively to prevent the risk altogether.
The Right Metals
It comes down to picking the right metal for the job. First, not all metals rust; for rust to occur, metals must combine with oxygen and water to form different oxide chemicals, most commonly iron oxide. Two metals are highly vulnerable: copper and iron.
That said, most roofers don’t use pure iron or unprotected copper for their materials. While copper is certainly a choice, galvanized steel is far more common. Steel roofing is great for rust resistance and has an outer coating of zinc – protecting most iron content in the material. This coating protects against rusting, while preserving the structural strength of the inner steel layer.
Even more common today is galvalume steel – which is protected by an aluminum and zinc alloy. This material is stronger than ordinary galvanized steel – lasting up to three times longer against rust. When you see an old, rusty metal roof, it’s usually an older galvanized design. Galvalume steel, on the other hand, can last as long as the metal in the most humid of climates.
Aside from the material itself, most metal roofs are painted, and this provides a protective coat that prevents rust as well.
Some roofers, such as Erie Metal Roofs, use stone-coated steel. This offers similar rust resistance as galvanized steel, but with the added appeal of a stone appearance.
What to Do if Your Roof Rusts
Though metal roofers take careful measures to prevent rusting, sometimes harsh weather can strip away the protective coating and damage the metal. In those cases, your roof should still be under warranty. You will want to avoid cleaning the rust yourself, however, as this may invalidate your warranty, losing you money.