ICFs Stand Up to Storms
Wednesday, May 25, 2011 at 05:46PM Hurricanes and tornados cause millions of dollars in damage each year to America's homes. Perhaps the best option is to build with insulating concrete forms, or ICFs. Hurricanes pose three main threats to a structure—strong winds, storm surge, and flying debris—and ICFs stand up well to all three.
Strong Winds and Storm Surge: ICFs stand up to hurricane force winds easily, thanks to the mass of concrete in the exterior walls.
ICF structures have another advantage: They are integrally tied to the footing or foundation slab with structural reinforcing steel. While frame walls use hurricane ties and/or anchor bolts to meet code minimums, ICF wall-footing connections are stronger by a factor of ten. Sometimes, the walls are poured monolithically with the footing, eliminating even the cold joint.
Likewise, all of the wall components above the footing are connected in a solid monolithic mass, eliminating flex, fatigue, and weak points. Photographs taken after Katrina prove the point dramatically: Often, a battered ICF homes stands relatively intact, even when the neighboring homes have been swept away or reduced to a bare slab.
One area of concern for code officials and the insurance industry are the roof attachments; it does little good to have hurricane-proof walls if the roof is compromised and belongings get ruined in the torrential rain. Once again, ICF homes have more hurricane-resistant alternatives available than other building methods.
Traditional roof trusses fastened into concrete are extremely sturdy. Steel trusses are even better. And ICFs are strong enough to support the most durable choice, a concrete roof system.
Flying Debris: The third major threat from hurricanes is flying debris. Dramatic photos show sheets of plywood skewering palm trees. Boards literally become missiles, and can puncture even brick walls.
Scientists at Texas Tech University have studied this issue extensively. In one experiment, eight-foot-long 2x4 studs were shot at various wall assemblies. They easily penetrated wood- and steel-frame walls at 50 mph. At 70 mph, they penetrated brick veneer. But nothing penetrated ICFs, even at 100 mph. (See a video of the tests at www.icfmag.com.)
The report concludes, “The strength and durability of concrete walls offer unmatched resistance to the devastation of major storms.
“The Best Wall Possible”
“Homes built with ICFs [are] sustainable structures capable of withstanding extreme weather conditions,” confirms Dr. Ronald Zollo. Zollo is a professor of civil and architectural engineering at the University of Miami and a licensed professional engineer. He led the team that surveyed the damage of 1992’s Hurricane Andrew.
Zollo says ICFs are stronger than competing concrete systems because of the concrete cure time and the monolithic structure of the wall. “It’s not an assembly of smaller components,” he says. “You aren’t dealing with fatigue issues, loosening of the structure, and deterioration. You have continuity throughout the structural system.”
“Homeowners and builders,” he continues, “need to move away from traditional structures that cannot withstand the type of lateral forces that extreme weather, such as hurricanes, can place on a home. The strongest wall is a concrete wall, and if we’re going to build a poured wall, let’s make it the best poured wall possible, and that wall is ICF.”
No Added Cost
Significantly, ICF construction does not cost significantly more than frame construction, and is often cheaper than CMU. Layne Thompson, an ECO-Block distributor in Desdin, FL, points out that wood-frame or concrete block construction requires significant work to meet hurricane-resistant standard, while “ICF walls are inherently stronger with no extra effort. There is no extra cost in the wall.”
Reader Comments (1)
I looked into a similar product a decade or more ago and the info supporting the quality of product was not all that strong. Now, many years later, it seems as if things have really improved. Not only in the product development side of things, but over all in the construction industry. Over time as products are used more and more, design and implementation improves. That is clearly seen today as with your ICF's. We are looking to build in the next year or so and most certainly be considering your products. Thanks for the information, Dave