When shopping for metal roofing and siding, purchasers must be vigilant to ensure the substrate they choose will match their long-term performance expectations. There are a variety of steel substrates available in the marketplace and the wrong selection could result in disappointment and reduced service life.
The most popular steel substrates in the metal roofing and siding industry are Galvanized and Galvalume. Galvanized substrates are coated with a zinc alloy, while Galvalume substrates are coated with an alloy of zinc plus aluminum. Both Galvalume and Galvanized are good substrates for metal panels.
With Galvanized substrates, the greater the amount of zinc the greater the protection against panel corrosion. Two commonly used Galvanized substrates are designated as G100 and G60. These designations relate to the total amount of zinc contained on both sides of the panel surfaces. G100 contains 1.0 ounce of zinc for every one square foot of panel while G60 substrates contain 0.6 ounces of zinc. The important fact to consider is that a G100 substrate contains 66% more protective zinc than a G60 substrate. This difference will have a direct correlation to panel longevity and long-term aesthetics of your project.
For most applications, Galvalume substrates offer the best long-term solution, and Galvalume's superior performance has been proven in the field. Over four decades of testing and field applications has shown that Galvalume delivers superior corrosion resistance compared to Galvanized panels. In fact, Galvalume's performance in the construction industry has been so superior, that steel mills warranty the substrate against perforation due to corrosion. Similar warranties do not exist for Galvanized.
The images in the section above are from an industry research project. Unpainted Galvalume and Galvanized panels were placed in four different types of outdoor environments, including normal marine and a rural setting. The harsher the surroundings, the better Galvalume performed. After 23 years of side-by-side comparison in all areas, Galvalume was two to four times more durable than Galvanized.
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