Recently, we had someone comment on one of our posts comparing asphalt shingles to metal roofs that we had failed to make, “…one mention of rust!”
But the fact of the matter is that rust might only be a consideration in some locations if you're comparing metal roofs that are priced similarly to asphalt shingles. Since asphalt shingles usually the cheapest roof material you can buy, metal roofs that are in the same price range are usually at the low end of the quality scale. Low quality metal roofs are cheap because they are most often made of the cheapest version of steel. Even then, if the roof were properly designed (i.e. configured to drain easily) and assembled with a minimum of exposed fasteners, a metal roof is likely to outlast a composition shingle.
Most of the better metal roofs on the market cost considerably more than asphalt shingles, but are very corrosion resistant and are famous for long lifespans even in regions with high humidity. The better roofs feature thicker gauges, more corrosion resistant metals, high-quality finishes, and more sophisticated profiles (to hide nails and screws). There are well-established reasons that spending a little more on a metal roof will make for a better, more weather-resistant material, and guarantee an exceptionally long service life.
All of these generalities can be negated however, and the commentator would be very accurate in mentioning rust in an area within a mile or so of salt water. And the warmer the climate, the worse the corrosive effect of salt water proximity. If our friend has a coastal home in Florida or the Caribbean, then he’s quite right in mentioning rust as an issue with a lot of metal roof options (although copper, stainless steel, and aluminum are all used regularly and successfully in such locations). For the rest of us, however, rust just isn’t an issue with the vast majority of metal roofs, and the higher-quality the metal roof, the less chance it will be a problem.
Have a burning metal roofing question of your own? Ask in the comments and we'll write a post to answer it for you!