Metal Roofing Near the Florida Coast: Galvalume vs. Aluminum and Salt Corrosion

Last reviewed September 27, 2026

What protects a steel roof panel

Galvanized steel is steel with a zinc coating (ASTM A653). Zinc protects the steel both as a barrier and by corroding first.
Galvalume uses a coating of 55% aluminum, 43.5% zinc and 1.5% silicon (ASTM A792). GalvInfo reports it corrodes 3.8 to 18.7 times slower than galvanized, depending on the environment.

U.S. Steel explains that salt water destroys the protective oxide films on aluminum and zinc, which makes both coatings corrode much faster near the ocean.

Warranty distance rules

Many steel panel warranties exclude homes close to salt water. One Galvalume warranty excludes buildings within 1,500 feet of a salt-water or marine environment. Sheffield Metals describes typical exclusions of 1,500 feet from breaking surf and 800 feet from a large bay. Each manufacturer sets its own distances, so read the warranty before you buy.

Aluminum for coastal homes

Coastal contractors quoted by the Florida Roofing and Sheet Metal Contractors Association say the usual choice on the coast is .040 or .050 aluminum with a PVDF paint finish. FEMA recommends stainless steel clips and fasteners within 3,000 feet of the ocean.

Metals that do not mix

The Metal Construction Association warns that copper corrodes steel, aluminum and zinc badly. Watch for:

Copper flashing, copper gutters, or water dripping from copper lines, including AC condensate lines.
Lead flashing touching Galvalume.
Pressure-treated lumber made with copper-based preservatives (ACQ, CA) in direct contact with panels. MCA says to separate them with a barrier such as roofing felt.
For marine exposure, MCA says 316L stainless is the minimum for stainless fasteners.

Paint: PVDF vs. SMP

A PVDF finish (sold as Kynar 500 or Hylar 5000) must be at least 70% PVDF resin. SMP is a less expensive paint that McElroy Metal says can micro-fracture when panels are formed. PVDF usually carries longer fade and chalk warranties, which matters under Florida sun.

5V crimp vs. standing seam

5V crimp and other exposed-fastener panels are screwed through the face. Sheffield Metals notes the rubber washers degrade in UV and screws can back out as panels expand and contract. FEMA points out one advantage: it is easy to see that all the fasteners are there. Standing seam hides its fasteners under clips that let the panels move with heat. It costs more.

Florida approval

Roofing products in Florida need state or local product approval (s. 553.842, F.S.). Ask for the panel’s FL number and look it up on the Florida Building Commission site.

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Frequently asked questions

Can you put a Galvalume roof near the ocean?

Many manufacturers exclude homes within about 1,500 feet of salt water from their Galvalume warranties. Check the specific warranty. Aluminum panels with stainless fasteners are the common coastal choice.

What fasteners should a coastal metal roof use?

FEMA recommends stainless steel clips and fasteners within 3,000 feet of the ocean, and the Metal Construction Association says 316L stainless is the minimum for marine exposure.

Is standing seam better than 5V crimp?

Standing seam hides its fasteners and lets panels move with heat. 5V crimp costs less, but its exposed screws and washers need checking over time.

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Metal roofing near the coast: Galvalume, aluminum and salt air