Living near the ocean has its perks—scenic views and fresh air—but the salty sea air poses challenges for roofing materials. Add on top of that, the occasional hurricane or tropical event and you have the harshest conditions imaginable for metal roofs as they weather our coastal environment. Salt causes metals to corrode quickly, which often leads to finish failures which can parlay into more serious problems. This is particularly true for homes within 3,000 feet of the coast, though it's advisable to use coastal-appropriate metals up to a mile from the shore. Many "metal" roof manufacturers provide NO WARRANTY for their metal panels if you live within this proximity to a saltwater source. That's right, NO WARRANTY! Yikes - many homeowners live without knowing the risk of the roof over their head. Galvalume is a commonly used material, which, as of the writing of this article, we've still yet to see covered by a warranty on our barrier island build sites. Galvalume has a steel core with a galvanic coating that protects from the elements - if that protective finish is scratched or damaged, you can bet your bottom dollar that corrosion (rust) will soon follow.
Understanding the pros and cons of various metal roof options is vital for homeowners to understand to be able to make the best informed decision for their coastal home. Here is a quick guide to help if you are considering metal roof options in a salt coastal climate.
Challenges for Coastal Metal Roofing
- Corrosion: Salt air accelerates rust and corrosion, compromising the roof's integrity.
- Exposed Edges: Scratched or cut metal can corrode if the edges are not properly sealed.
- Color Fade and Chalking: Coastal climates with intense UV exposure and reflective water can lead to quicker color fading and chalking on painted panels. A PVDF paint system (Kynar or equivalent) is similar to a car's exterior finish...which is great, unless you keep your car on a roof with a high exposure to sun.
Top Metal Roofing Options for Coastal Areas
1. Aluminum Core (NOT STEEL WITH A COATING!):
- Advantages: Highly resistant to rust, lightweight yet strong, and cost-effective. PVDF paint enhances its corrosion resistance. When aluminum does oxidize on the surface, it provides protection to itself from further oxidation (similar to how copper forms a patina). Aluminum does not darken with oxidation and the roof runoff does not carry trace elements that might cause issues with other surfaces that it comes in contact with. Aluminum has a relatively low affinity for electrons
- Costs: Installed, 5v corrugated panels range from $12 to $14 per sq. ft., while standing seam panels are $15 to $17 per sq. ft.
- Ideal For: Those seeking a balance between affordability and durability.
- Disadvantages: Not very malleable.
2. Copper:
- Advantages: Exceptional corrosion resistance and longevity, as seen with the Statue of Liberty's patina. Very malleable, best for hand-crimping and forming.
- Costs: Standing seam panels range from $18 to $22 per sq. ft. installed.
- Ideal For: Higher-budget projects where long-term investment and aesthetic appeal are priorities.
- Disadvantages: Patina will stain almost anything it drips or runs onto! Phone signals have issues penetrating copper roofs
3. Stainless Steel:
- Advantages: Durable but less common and harder to paint, making it less practical for many.
- Costs: Generally higher than other metals, with limited availability and higher pricing.
- Ideal For: Specific projects where budget is less of a concern and durability is essential.
- Disadvantages: Weight, cost, and not very malleable.
4.Zinc coated products (copper for example):
- Advantages: Good performance and longevity, with a lifespan of 60-80 years. No patina running. Malleable product that is easy to hand crimp.
- Costs: Standing seam panels range from $14 to $30 per sq. ft. installed.
- Ideal For: Those who want a long-lasting material with a distinctive look.
- Disadvantage: Cost.
Additional Considerations
- Hurricane Protection: Metal roofing can withstand high winds and protect against water damage, making it a good choice for hurricane-prone areas. Make sure your product is rated for use in 140+ mph (code for the SC Coastal Zone).
- Maintenance: Metal roofs are low-maintenance, though coastal installations may require annual or bi-annual cleaning.
In summary, aluminum is a good and popular choice for coastal roofing due to its balance of cost and corrosion resistance. Make sure you are getting roof panels with an aluminum core, not a steel core with an aluminum coating. Copper and zinc offer more longevity but come at a higher price. Always avoid using steel core products in coastal environments due to its susceptibility to rust. Consider the Galvanic Series of metals which lists metals in the order of their nobility. Noble metals are those that are resistant to corrosion and oxidation. When two metals are immersed in an electrolyte (i.e. moist warm air), the less noble metal experiences galvanic corrosion. The rate at which it corrodes depends upon the medium (in this case, the electrolyte) and the difference in nobility of the two metals. You should never have a metal with a higher nobility (i.e., a copper chimney shroud, copper roof, or even copper flashing) that drains onto a metal roof with a lower nobility as this will greatly accelerate the rate of erosion of the less noble material.