No roofing material is flawless, but steel is arguably the closest to perfection. It’s durable, long-lasting, lightweight, energy-efficient, sustainable, and charming. Its price is greater than that of an asphalt-shingle product, but its cost is moderate compared to the true premium materials on the market.
Steel, however, has one inherent weakness: corrosion. Since it contains iron, it develops rust when exposed to moisture and oxygen. This disadvantage may shorten its life span or increase its maintenance needs.
Fortunately, steel roofing products these days come with a protective coating to delay corrosion. When planning a new roof construction or replacement project, you can choose from galvanized and galvalume steel roofing.
What’s the difference between the two? CQ Roofing talks about when to select which:
When to Choose Galvanized Steel
Galvanized steel is where the substrate is covered with zinc as its protective skin. The outer metallic coating envelops the rust-prone alloy, safeguarding it from moisture and oxygen. Zinc itself has exceptional corrosion resistance.
The best thing about galvanized steel is its ability to recover from scratches. Zinc has a self-healing ability, making it an excellent sacrificial layer.
Any honest residential roofing company, like CQ Roofing, would say that the zinc coating of galvanized steel doesn’t last forever. Its longevity depends on its thickness, so the thicker means the better.
Furthermore, rust tends to develop on non-vertical areas of a galvanized steel roof. To slow down the process of corrosion, use galvanized steel if your roof design has few or no low-slope sections to drain water more efficiently.
When to Choose Galvalume Steel
Galvalume steel is a popular choice for metal roof replacement. This material is similar to galvanized steel except that it combines zinc and aluminum; hence the name. The addition of aluminum enhances the corrosion resistance of zinc, which is why the two makes a formidable protective coating.
The drawback of galvalume steel, however, is susceptibility to tension bend staining. This phenomenon happens when the metallic coating becomes thinner over areas with tight bends and deep folds. The thin sections have a tendency to form microscopic cracks, which may expose the substrate to the elements.
Moreover, aluminum decreases zinc’s ability to self-heal, which is why galvalume steel can’t recover from scratches as effectively.
Despite this irreversible downside, galvalume steel is a clever choice for roofs with simple profiles. The fewer bends and folds your roof design has, the more durable galvalume steel becomes.