Metal Roofiing Profiles
When it comes to metal roofing products best used, we’ve learned through testing and experience that metal is susceptible to corrosion from salt — some products less than others and if you’re installing near the ocean, it’s important to know which products work well and which do not perform well in these environments.
Zeroing in on specific metal roofing profiles and products for the Coastal Regions of the United States is a bit challenging — mainly because there is a lot of coastland. Did you realize that 23 of the 50 states have an ocean coastline?
When it comes to metal roofing products best used along the coast, we’ve learned through testing and experience that metal is susceptible to corrosion from salt — some products less than others and if you’re installing near the ocean, it’s important to know which products work well and which do not perform well in these environments.
The general consensus is that galvanized steel is not a recommended choice for installations near the ocean. The salt air damages galvanized steel in a hurry.
There are plenty of workable solutions. In the Architectural Sheet Metal Manual published by the Sheet Metal and Air Conditioning Contractors’ National Association you can find plenty of information regarding metals applications and specifications. Aluminum, copper (in air and moisture), lead (atmospheric), stainless steel and tern-coated stainless are listed as “corrosion resistant metals.”
“For coastal areas, roofing materials must be extremely resistant to corrosion as well as wind uplift,” says Ed Thomas, vice president and general manager at Follansbee . “For that reason, standing seam metal roofing functions as a practical choice. Many metal roofs are guaranteed to withstand winds of 120 miles per hour and meet strict Miami-Dade certification codes. In addition, many metal roofing materials are extremely resistant to corrosion.
“When properly installed, stainless steel metal roofing products coated with alloys comprised of a mixture of zinc and tin will provide the highest level of corrosion and condensation resistance available,” Thomas says. Follansbee’s own terne-coated stainless steel roofing materials coated with patented ZT (zinc/tin) alloy have surpassed 29,750 hours of ASTM B 117 salt spray testing with no signs of red rust.
“Other alloys, coated over metals like zinc, aluminum and copper, can also provide enhanced corrosion resistance, and will normally pass between 2,000 to 3,000 hours of salt spray testing,” Thomas says. “It is important to note that chromate, which is used in galvanized roofing, is prone to corrosion and water wash out due to rain, so it should be avoided if specifying a longer lasting metal roofing material is a concern.”
Many in the industry believe this is becoming more common knowledge, but it bears repeating — the least expensive education you can get is learning from someone else’s mistakes.
“The continued improvements in testing standards and awareness of the quality of metal roofing have contributed to an increased level of awareness on the part of the architect and consumer,” Thomas says. “This has led to architects and consumers turning to higher quality metal roofing materials for coastal areas.”
Fasten it right
In addition to battling saltwater conditions, hurricane force winds usually require installers to rethink their approach to installation. Many manufacturers will provide tips for installing their products in high-wind areas. The safest recommendation is to follow the codes — they’re in place for a reason.
Many metal roofing systems are tested to perform in coastal environments by meeting the Florida Building Code or the stricter Miami-Dade Building Code.
Paint it right
Polyvinylidene fluoride (PVDF) coatings, manufactured from Kynar 500 and/or Hylar 5000 resins, are generally regarded as the top-of-the-line coating for metal roofing panels and shingles. Arkema , the manufacturers of Kynar 500, has a paper on its website, titled, “70% PVDF Coatings for Highly Weatherable Architectural Coatings.” Regarding the durability of PVDF coatings, it says:
“Based on many field experiments, it appears that even the best polyester paints can survive no more than about four or five years in a humid, sub-tropical environment, before significant gloss loss and chalking occur. This may be due both to the photochemical degradation of the polyester polymer backbone, and to the degradation of the crosslinks. Many of these structural features are also shared by some other kinds of fluoropolymer coatings, such as fluorinated ethylene vinyl ether (FEVE) coatings. However, the PVDF resin does not share these features, and is more highly fluorinated and more inert — which may explain its superior weatherability.”
For coastal metal roofing installations, Taylor Metal Products of Salem, Ore., offers MarineGuard, a paint system using PPG’s Duranar SPF Coatings. Applied to 24-gauge Galvalume/Zincalume steel, MarineGuard consists of a .45- to .65-mil primer; a .70- to .90-mil top coat and a .45- to .65-mil clear top coat to hold up best in aggressive saltwater and marine environments.
“It’s developed by PPG as an extra to their Duranar line,” says Keith Bailey, owner of Taylor Metal Products. “As far as I know, we’re the only ones who have branded it and market it as a paint system for use in saltwater area applications.”
Because paints deteriorate at a faster rate in saltwater environments, MarineGuard is one method to extend the life of the product, Bailey says. “It’s for high-end residential applications and signature commercial applications; any applications where the look is important.”
Taylor’s MarineGuard was employed as part of the roofing system on the Ketchikan Public Utilities Building in Ketchikan, Alaska. Andy Rauwolf of Tongass Construction, L.L.C. , in Ketchikan, was asked about recommendations for the project — to replace a metal roof that was about 20 years and had looked “shabby” for more than 10 years. The building is across the street from the ocean.
Rauwolf inquired about MarineGuard and the information supplied by Taylor was enough to convince all concerned to give it a shot. The job was completed last August.
“We had some pretty nasty storms this winter, 100 mph winds, and it looks like it did the day I installed it,” Rauwolf says. “With the environmental issues we face, it’s nice to have these assurances. It is a little more expensive, but in the long run it will be worth it.”
Bailey says there is an additional cost to the system and it’s not as practical for small orders, as all orders are custom. The Ketchikan Public Utilities Building was about 6,000 square feet and done in Tile Red. Each year, Taylor Metal sells MarineGuard on a handful of projects and most are residential.
All manufacturers will warn you about the dangers that stem from installing a metal roofing product near the ocean. It makes sense to choose a product that will endure.
From Metal Roofing Magazine