Aluminum vs. Galvanized/Galvalume Metal Roofs
June 9, 2023 | By Bryan Rusch | Filed under: Articles, Education, Metal Roofing, Technical
It can be difficult and overwhelming when deciding which metal is the best choice for your metal roof project with so many products on the market. One of the biggest decisions to make is the metal you will use. That's why our expert metal roofing contractors at Classic Metal Roofs in CT, MA, RI, and NH will give you a complete breakdown of aluminum metal roofs vs. galvanized/Galvalume metal roofs.
All Metal Roofs Are Not Created Equal
Metal roofing in New England offers many benefits that cannot be disputed. When seeking these benefits, one must be careful because not all metal roofs are created equal, nor are they installed in the same way. When building a metal roof, the base metal used for the roof is a major and crucial choice, especially for residential applications.
First, it's important to note what the "base metal" is in the construction context. The base metal is the primary component used in construction material, from the sheets of roofing exposed to the elements to the fasteners contained beneath the metal roof. In roof assembly, base metals can be steel, aluminum, copper, zinc, or even a combination of these base metals. Each base metal has advantages and disadvantages regarding lifespan and appearance.
The two base metals we will focus on in this article are widely used for metal roofs in New England and beyond aluminum and galvanized steel (galvalume).
- Aluminum – Aluminum is a silvery-white, soft, nonmagnetic, and ductile metal primarily used for architectural roofing that doesn't require structural integrity.
- Steel – Steel is a hard, strong, gray, or bluish-gray alloy of iron with carbon and usually other elements. It is used extensively as a structural and fabricating material for structural and architectural roofing.
Galvanized & Galvalume Steel Roofing
Base metals are often combined, coated, or layered with other metals in a variety of bonding processes, allowing for more custom options and strengths to match the specific project. Two popular roofing materials that use this process are galvanized and Galvalume. Each of these roofing materials is made of a steel base metal coated with zinc for an extra protective layer against rust, creating galvanized metal. Galvalume is made of a steel base metal coated with zinc and aluminum to protect the steel from rust.
What Happens When the Protective Coating Wears Off?
Rust is very common, and everyone has encountered rust at some point in life. It can range from unsightly to disastrous. One place you don't want to see rust is on your metal roof. That leaves the question of which base metal assures no rust over the roof's life. In our experience, only one of the three base metals is rust-proof. That base metal is aluminum.
The nature of metal roofing involves bending, cutting, and shaping the metal to form the roof. All this metalwork contributes to stresses on the metals and exposure of edges where a base metal may lose the protective zinc or aluminum coating. This is especially true for galvanized and Galvalume roofs where the base roofing is steel. Because of the nature of metal roofing, galvanized roofing is particularly susceptible to rust. Protective coatings naturally give way to the base metal.
When you choose to install an architectural aluminum metal roof, you won't have to worry about when your new metal roof will start to rust. You'll have the peace of mind that comes with choosing a metal roof designed to last a long time. Aluminum is one of the materials used to coat Galvalume roofing because it doesn't give way to rust.
Tthe drip edge and rib bend in the Galvalume standing seam roof of the same home. If you examine the photograph closely, you will see the paint finish has chipped away underneath the drip edge, where the steel base metal has begun to deteriorate (rust).
A Galvalume metal roof failure on a commercial building.
The photo above shows a galvanic reaction occurring, through the paint finish, no less, of a steel-based roof underneath the flashing of a drip edge above. This would not happen with a Kynar resin paint-finished aluminum roof.
Aluminum Offers Long-Lasting Protection
All galvanized or Galvalume metal roofs come with paint finish warranties which are key to understanding the expected longevity. Aluminum roofing also comes with paint finishes, but they have their own warranties. The biggest difference is that aluminum will oxidize/chalk if exposed to the elements but won't look unsightly. On the other hand, steel will continue with a rapid oxidation process (rust) and look unsightly and worn.
Contact Classic Metal Roofs
Let Classic Metal Roofs install a non-rusting aluminum metal roof for your next architectural roofing project. Contact us for a free estimate and more information on Galvalume metal roofs and aluminum roofs.
