Galvanized Metal Roofs – Why Use G90 or Higher for Residential Roofing?

Galvanized panels are a very popular substrate for metal roofing.  Manufacturers often use terms such as G60 or G90 to describe their products.  What’s the difference? And which should contractors use in various applications?

Galvanized Defined

Galvanization is the process of applying a protective zinc coating to steel or iron, to prevent rusting.  After roofing panels are galvanized, they can be painted or granular-coated.  The grades of galvanized products correspond directly to anticipated field longevity. With galvanized substrates, the more zinc the better. These “G” numbers indicate how many ounces of zinc are applied to each 100 sq. feet of paneling. G60 has 60 ounces, G90 has 90 ounces and therefore provides better corrosion resistance. These numbers are directly related to increased longevity and long-term aesthetics for the roof.

Specifications Defined

The Metal Construction Association has developed a Guide Specification for Residential Metal Roofing that clearly defines which galvanized products should be used on homes. All MRA members must agree to adhere to or exceed the MCA’s Guide Specification for Residential Metal Roofing before they are permitted to join the association.  This same rule applies for both manufacturers and contractors.  For galvanized steel used in residential applications, the MRA recommends a minimum metallic coating of G-90. So, if you’re not sure of the coating of the panels you are installing on homes, it’s in your best interest to find out.  Again, the higher the number, the better protection from rust.

Metal Roof

Why It Matters

“Members of the metal roofing industry are constantly fighting the outdated ‘rusty barn roof’ image, and the Metal Roofing Alliance has made great progress in educating consumers about today’s beautiful, long-lasting metal roofing options.  Every bad roof installation is a step in the wrong direction,” says MRA’s Executive Director Bill Hippard.

Metal Roofs on Homes should not rust

In a competitive environment, it may be tempting to choose a lower quality (and therefore lower cost) steel panel when installing a new metal roof.  However, for roofers who are looking to build a business and remain in this growing residential market segment, that choice offers short term gain in exchange for long-term pain.  Whenever a lower-quality metal roof is installed, it’s almost certainly doomed for failure, resulting in customer complaints and a damaged reputation for all metal roofs.

Former customers are an excellent referral source, and a happy homeowner will recommend your business to their friends and neighbors.  The opposite is also true – install an inferior product, and you will hear about it as well as those same friends, neighbors and perhaps even the local licensing authorities.

For a list of MRA member manufacturers and the Investment Grade Roofing products they offer for residential installation, please visit our website.

5 thoughts on “Galvanized Metal Roofs – Why Use G90 or Higher for Residential Roofing?

  1. Thanks for posting this! I’m looking into having a metal roof installed on my home this summer. One of my friends told me that he heard that I should go for a metal roof that uses G90 or higher, so I’m trying to find information that explains why it matters. Now I can see why it’s important to have it galvanized using G90 or higher. One of my main concerns with installing a metal roof is if it ends up rusting after years of wind and snow. Using G90 galvanization seems like a good way to prevent it from rusting.

  2. I would have to agree that it’s better to choose higher quality metal roofing materials. You have to look at the long-term consequences of your decisions. By having higher quality materials you can assume that your rood will last longer and look better than the lower quality materials.

  3. Thanks for explaining what galvanized means and about the different levels of galvanization. I haven’t really considered a metal roof before, but after reading this, I might have to look at that as an option. We need to replace our roof in the next year or two because it’s over 20 years old now. I’ll have to talk with my husband about metal options. Thanks!

  4. Thank you for going through and explaining what it means to galvanize your roof. I can see how this process can help to solidify and ensure that the installation of the roof is correct and thorough. I definitely agree with Bill Hippard when he says that every bad roof installation is a step in the wrong direction, so going through the right steps and using the right techniques and materials will ensure that you do so. Overall, I will definitely make sure that I am aware and efficient in my roof installation.

  5. So if I wanted to use a metal type that was higher than G90, what type would you recommend? I live not too far from the ocean so I would want something that would withstand the salty air. The roof that is on my home now isn’t doing the best job and there are a couple rusty spots. Perhaps once the weather warms up, I’ll see about getting it replaced.

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