Galvalume vs. galvanized roofs: which is right for you?

Image source: Roofing Magazine

Chris Gennone

By Chris Gennone

May 13, 2021

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If you're looking to install a metal roof, you've probably heard of two different kinds of steel-based materials, galvalume and galvanized steel. Both are commonly used for both residential and commercial buildings due to their low price point and durability – but what's the difference between the two? Which is better for your home? In this article, we'll discuss the differences between galvalume and galvanized roofs, their benefits and disadvantages, and determine which is right for you.

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What are galvalume and galvanized steel?

Galvalume roof on a residential home

Image source: Sheffield Metals

Galvalume

Introduced by Bethlehem Steel in 1972, the galvalume process combines a steel base with aluminum, silicon, and zinc where a steel sheet is hot-dipped in aluminum and zinc alloys. This combination prevents oxidation and corrosion. The zinc coating also protects any scratches on the galvalume metal from rusting.

Galvanized

While the galvalume process is relatively new, galvanizing has been used for nearly 200 years. Galvanization includes a carbon steel sheet that is dipped in molten zinc, forming a strong alloy coating that prevents corrosion. Galvanized metal used to be a popular item decades ago but became harder to find as galvalume became more popular.

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Galvalume vs. galvanized

Though both their processes are very similar, there are some subtle differences and uses for them. Let’s dig into the details.

Corrosion

Corroded metal roof

Image source: AZO Materials

Galvalume - Both galvalume and galvanized metal are corrosion-resistant thanks to their zinc coating, but if the coating wears down over time or is scratched in any way, it can lead to corrosion. Galvalume's biggest benefit and edge over galvanized metal is the addition of aluminum, which is naturally resistant to corrosion.

Galvanized - While galvanized metal is also resistant to corrosion, it is not as resistant as galvalume and is also prone to forming red rust if its zinc coating becomes scratched. Because of galvalume's superior corrosion resistance and durability, the majority of metal roofing has shifted from galvanized to galvalume.

Uses

Galvalume steel roof on a commercial building

Image source: Puyat Steel

Galvalume - Galvalume steel is most commonly used for roofing and walls for both commercial and residential buildings, in addition to industrial spaces. Although, it is not recommended to use galvalume metal roofing for buildings with animal confinement. The greenhouse gas emissions from manure react with galvalume's zinc coating, which breaks it down and degrades the metal.

Galvanized - Galvanized metal is used for a variety of similar applications, but is often harder to install. Like galvalume metal roofs, galvanized metal works better in drier climates where excess salt and water are less of an issue.

Cost

Galvalume - For a galvalume roof, you can expect to pay anywhere from $75-$200 per square. Though it's more expensive than asphalt shingles, galvalume steel is still relatively cheap among other types of metal roofing materials.

Galvanized - Though galvanized steel is made very similarly to galvalume metal, it does run a little more expensive. You can expect to pay somewhere between $150-$350 per square for a galvanized roof.

Warranty

Galvalume - Galvalume steel panels and siding often come with several warranties including paint and a 25-30 year warranty, which protects against rust-throughout, but not surface rust. Some companies, like the Union Corrugating Company, do not offer protection for homeowners in coastal climates where the metal is subject to excess salt or freshwater.

Galvanized - One of the biggest disadvantages to galvanized metal roofs is the lack of substrate warranties, due to their unpredictability in specific climates.

Lifespan

Galvalume steel roof installed on a commercial building

Image source: All American Steel

Galvalume - Though both galvalume and galvanized roofs have a longer lifespan than most roofing materials, galvalume roofing panels can last up to 60 years with minimal repairs.

Galvanized - Galvanized steel can last up to 50 years or more with minimal repairs, depending on the climate you live in.

Pros and cons of galvalume and galvanized roofing

Galvalume steel roof installed on a residential home with palm trees in the background

Image source: Rausa Builders Corp.

Pros

More cost-effective - Though metal roofs are typically more expensive than most other roofing systems, galvalume and galvanized metal roofing are more cost-effective than most other metals, such as a standing seam metal roof. A standing seam roof can cost at least double the amount per square foot as steel.

Resistant to corrosion - While both galvalume and galvanized metal panels are resistant to corrosion, galvalume offers extra protection due to the addition of aluminum, which is naturally resistant to corrosion.

Lightweight - Galvalume and galvanized roof panels are incredibly lightweight with a high strength-to-weight ratio, ensuring the galvanized and galvalume coatings don't crack as easily.

Self-healing - Galvalume steel roofing typically features unpainted, exposed cut edges where small areas of red rust are normal but has self-healing characteristics that stop the spread of rust with an acrylic galvalume coating or paint. However, galvanized steel does not have self-healing properties and is prone to rusting if the coating becomes scratched.

Energy efficiency - A galvanized and galvalume steel roof is incredibly energy efficient due to its ability to reflect solar radiant heat and is even Energy Star certified. And because of the hot-dipping of zinc in both galvalume and galvanized steel, these coated metals are made from incredibly abundant elements which don't harm the environment.

Cons

Oil canning - The biggest disadvantage of galvalume panels is oil canning. Oil canning is when flat surfaces of the roof or wall panels appear to be wavy or distorted looking. Although it does not signify any structural damage or quality to the metal, it's not very aesthetically pleasing.

While galvalume and galvanized roof systems have similar properties and offer similar uses, there are some subtle differences. Galvanized steel used to be more commonly used in previous decades, but more homeowners have shifted their attention to galvalume roofing.

Using galvalume steel is not only cheaper, and longer-lasting than galvanized steel, but it's also more readily available whereas galvanized steel is harder to find. Although both are viable options, if you live in a coastal environment, we recommend not opting for either of these because they may not meet warranty requirements. Typically, other metals like aluminum and stainless steel alloys perform better in coastal climates because they don't depend so much on a galvanized coating. However, there are special coastal paint systems available that incorporate a high build primer and a clear coat which helps protect it from corrosion.

Either way, if you're interested in installing a metal roof, you really can't go wrong with galvalume or galvanized steel. Galvalume offers more benefits for residential and commercial buildings, but both roofing products are a highly durable, long-lasting option for your roof.

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