Metal Roofs vs. Hurricanes

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When it comes to hurricanes, roofs in general have two main enemies: strong winds and wind-driven rain. The Insurance Institute for Business and Home Safety estimates that roof issues comprise 85 to 95% of all wind-related property losses reported each year. The percentage may be even higher in the Mid-Atlantic states, especially those along Hurricane Alley.

In the case of North Carolina, it’s been said that nearly the entire eastern two-thirds of the state has experienced sustained hurricane-strength winds sometime during the past century. In 2003, Hurricane Isabel brought with it the strongest double-whammy of hurricane-force gusts and heavy precipitation in recent history. And it can happen again.

hurricane isabel

Hurricane Isabel making landfall in North Carolina’s Outer Banks on September 18, 2003.

One of the best ways to protect your home and your household against hurricanes is to install a metal roof. Metal roofs have been known to withstand wind gusts of up to 140 miles per hour and to hold up well against sustained abuse from hailstorms and heavy rain and snow. Their ability to resist uplift and water penetration is due to a combination of three main factors:

Factor #1: Design
Metal roof designs can be classified as either hydrostatic or hydrokinetic. Hydrostatic systems create a barrier against water, while hydrokinetic systems are built to shed water.

types of metal roofing systems

  • Hydrostatic (for low-slope roofs). These metal roofs have standing seam panels with joints raised above the roof’s water line. They provide protection against water infiltration under hydrostatic pressure.
  • Hydrokinetic (for steep-slope roofs). These metal roofs have slopes greater than 3:12 to facilitate water shedding. Their underlayment offers a secondary layer of protection against water infiltration (although not as much as the membrane used in hydrostatic roofing systems).

Factor #2: Installation

While a metal roof’s resistance to water infiltration is mostly determined by its design, its uplift resistance is more a function of the installation methods used. For this reason, the metal roofing industry is strict about following manufacturers’ installation instructions and local building code requirements.

Bodies like the Federal Emergency Management Agency (FEMA), the International Code Council (ICC), the American Society of Civil Engineers (ASCE), and the Institute for Building Technology and Safety (IBTS) have actively contributed to reference guides and technical fact sheets on the installation of metal roof systems in high-wind regions.

organizations

Components that affect how well a metal roof resists wind uplift include:

  • Flashing and trim (hip, ridge, rake, eave)
  • Clips
  • Fasteners
  • Nailers
  • Snap-lock seams (in the case of standing-seam metal roofs)

Factor #3: Metal’s Physical Properties

According to the American Iron and Steel Institute (AISI), steel roofing panels weigh about one and a half pounds per square foot. Steel has the best strength-to-weight ratio of any roofing material—a fact that can serve you well in the event of a hurricane.

Metal in general is also not as prone to the aging and degradation common to most other roofing materials when exposed to the elements. It offers long-life durability, making it especially suitable for areas where extreme weather isn’t unheard of.

As for rust resistance, steel sheets, tiles, and panels can be coated with zinc or zinc/aluminum to reduce their corrosion potential. They can also be alloyed with other materials to improve their rust resistance or coated with acrylic gel, paint, or colored ceramic coatings. Other metals used for roofing, like copper, lead, and tin, have natural corrosion resistance.

 

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Author Bio:

Austin Jones is a Marketing coach and works at Roof Roof based in North Carolina. With his expertise in roofing industry, he has worked with clients in many different places in the United States as well in Southeastern since 1995. His team of experts helps meet all the client’s pressures and multiple demands. As part of the company we help the homeowners as we are fueled by our desire to partake in our knowledge through our personal blog site.

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Sources:

https://www.disastersafety.org/high_winds/page/3/
http://www.fema.gov/media-library-data/20130726-1644-20490-8474/757_apd_7_metalroof.pdf
http://www.facilitiesnet.com/roofing/article/Metal-Roofs-Compare-the-Different-Systems–9806
http://www.ibts.org/services/innovation/best-practices/metal-roofing.pdf
http://www.atas.com/ATAS/files/67/67df6717-a0b3-41d5-a1b9-5375891de4a1.pdf
http://www.midatlantichurricanes.com/NorthCarolina.html

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