If you are one of the many homeowners looking to install a steel roof on your home, understanding the difference between galvanized steel vs. Galvalume is essential to getting the top performance you expect from your new metal roof.
Right off the bat: In most residential steel roofing applications including near-coastal areas — beach homes located near the ocean shore, and even homes located in the middle of heavy salt-spray — severe marine environments, Galvalume steel will be a better and more corrosion-resistant option than G-90 galvanized steel.
The one exception when Galvalume should not be used: Galvalume steel should not be used on, in, or around concrete or mortar. Concrete and mortar are highly alkaline environments.
Did you know? Bare Galvalume steel and painted Galvalume sheets will suffer rapid corrosion when in contact with mortar and concrete. Bare galvanized G-90 steel and especially Kynar 500 painted galvanized G-90 steel will perform better in this type of environment.
Now, because aluminum, one of the two metals in Galvalume coating, provides a barrier protection for steel, instead of galvanic or self-healing protection in galvanized steel, scratches and cut edges in Galvalume are less protected.
Galvalume steel is best for use in prefabricated metal wall panels and standing seam metal roof applications with concealed fasteners.
We would not recommend using Galvalume panels with exposed fasteners like corrugated or ribbed steel roofs.
Normally, Galvalume is offered in both bare and pre-coated (pre-painted) versions. Most residential-grade Galvalume metal roofing products – like galvanized steel – are coated with Kynar 500 or Hylar 5000 paint finishes.
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Galvalume has an excellent performance lifespan in bare exposures (unpainted panels) as well. Both galvanized steel and Galvalume weigh 100 to 150 pounds per 100 square feet and contain about 35% recycled steel post-consumer content.
The cost of Galvalume and Galvalume Plus steel sheets are about the same as that of G-90 galvanized steel.
A product called Galvalume Plus features an extra coating of acrylic. One advantage of Galvalume Plus is that it can be roll-formed dry, without vanishing oil. Thus, Galvalume Plus is very easy to form and install safely in the field, using portable roll-formers.
What is galvanized steel:
Galvanized steel was invented and developed for commercial use in the first half of the 19th Century, so it has nearly 200 years of proven track record. Carbon sheet steel is dipped in molten zinc. It’s more than a coating, however. A chemical bond occurs and produces the telltale “spangles,” the crystalline surface pattern found on galvanized steel.
Tip: Look for G-90 galvanized steel for residential applications not G-60
