Metal vs. Mother Nature (hurricanes and high winds)

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Manufacturers do their best to ensure products can handle big winds /

Metal roofing stands up to the forces of nature as well as or better than any type of roofing material and you should know how to sell that benefit to your customers. This is the first in a six-part series on how metal roofing holds up against Mother Nature. Each part will focus on a different phenomena, the first being hurricanes and high winds.

Mother Nature knows how to dish it out. Your customers want a roof that can take it.

Fortunately, if you’re installing metal roofing, you are armed with the right stuff!

There are two key ingredients to a successful roofing project — the material and the installation.

Butler MfgThe Roofing Industry Committee on Wind Issues was established more than 20 years ago to “identify and address important technical issues related to the cause of wind damage.” In 1999, the focus of RICOWI was broadened to include “other weather topics, and ‘Wind’ in RICOWI’s name was changed to ‘Weather’ to reflect the expanded scope.” With a team of volunteers from the roofing industry, RICOWI investigates events that include hail, energy efficiency and durability effects as well as hurricanes. (Learn more at www.ricowi.com.)

In RICOWI’s Hurricane Katrina investigation, it was determined “roofs designed and detailed according to current codes and standards will perform satisfactorily. Older roofs with little concern for the magnitude of the wind pressures at eaves and corners, and roofs installed with poor practices that lead to progressive failure of the roof membrane, were consistently the ones with significant damage.”

That’s good news. The newest materials and most modern installation techniques are standing up to hurricanes. So, when you’re installing a roofing system in an area where hurricane force winds could be a factor, install it right!

How can you make sure the metal roofing you install will stand up to hurricane-force winds? You have to work with your manufacturer to ensure you’re installing the proper panel and system as well as make sure the installation meets the code requirements.

Butler Manufacturing offers two roofing profiles with Miami-Dade certification — the MR-24 roof system and the Butlerib II. The MR-24 is a mechanically seamed trapezoidal panel and the Butlerib II is a through-fastened R-panel. Both have FM Global approval.

“For us, the MR-24 has performed well in hurricane zones,” says Mark Henry, Butler’s senior research engineer. “It’s been around since 1969 and has a great track record. I’ve been on roofs that were 30 years old and they’ve shown no signs of failure; the seams looked good and were weathertight. We even pulled apart the laps and the sealant was still soft. These are roofs that were predicted to last 30 to 35 or 40 years. Metal roofing panels have that longevity and durability. The life-cycle cost of metal panels is better than conventional roofs.”

Like most metal roofing manufacturers, Butler has invested thousands of dollars on testing and recertifying its metal roofing products. In 1959, Butler constructed a research center where its engineers test panels in wind uplift and missile tests. Before any panels and roofing systems are tested for certification at a lab, they are tested at the Butler center. It’s a major investment, but it prevents costly surprises at the test lab.

Henry has been intimately involved with testing of the MR-24 panel for more than 15 years and his work is seen in every drawing for every building. “First and foremost, we want our installers to take the time to work safely,” he says. Every Butler building has drawings that guide the builder through the installation process. One example of how the installation process is simplified to help ensure a perfect install is all purlins arrive at the site with pre-punched holes for fasteners to help keep the structure modular.

“We try to make the drawings and details straightforward and simple,” Henry says.
The difference between a Butler roofing system installed in a hurricane zone and one installed somewhere outside high wind areas is purlin spacing. There are three “areas” of a roof.

  • Field — main area of roof, where roofing system is under the least duress from wind.
  • Perimeter — the outside edges of any roofing section exposed to a substantial amount of wind uplift
  • Corner — approximately a 10×10-foot section where wind uplift most affects the integrity of the roofing system

Where the wind uplift is most severe is where purlins should and must be installed closer together. Henry says for most applications, purlins are spaced up to 5 feet apart in the field section of the roof. In corner areas that will face extremely high wind uplift, purlins may need to be installed as close as two feet on center, according to Henry. Naturally adding purlins adds to the expense, for both material and labor, but the system installed to its engineered requirements will stand up to Mother Nature’s rudest winds.

Florida tested, DECRA approved
High winds, heavy rains and flying debris are always a concern during a hurricane. The Villages of Sandalwood Lakes North, located in the High Velocity Wind Zone of Florida, was a mansard application that needed a new roof. A plan was in place to re-roof the complex over an extended period of time. After the busy 2004 hurricane season, the association stepped up its re-roof schedule so a new roof would be in place for the next hurricane season. DECRA Tile in Terracotta was chosen for the project.

MN-DECRA1A roof is vulnerable during a hurricane, not only is there the chance that it can be damaged by flying debris or it can be blown off and become flying debris. When making its decision, the homeowners association was looking for a roof that could withstand the high winds and provide protection from debris. The vertical wall presented by the mansard style of the roof was the perfect target for flying debris.

This was clear after hurricane Francis. Located across from the Villages is Sandalwood Lakes, a larger related mansard roof complex that had already been re-roofed with DECRA.

The Villages sustained a lot of damage after Francis from branches hitting the existing wood shakes, flat roofing pieces that impacted the mansard roof and wind-shear uplift. Conversely, the Lakes had no damage, protected by its new DECRA roof.

Since the project was in a high wind area, steel hat section purlins were used instead of nominal 2 x 2 wood battens. The versatility of the product made it easy to tailor the roof system to the project, thereby giving the owners the best installation possible.

DECRA products have been tested for Miami-Dade county approval. With the use of additional fasteners, DECRA Tile meets the requirements for this stringent approval, 150 mph. The interlocking structure and unique horizontal fastening method further enable DECRA products to withstand high winds and add to wind-shear strength in these hurricane-prone zones. 

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