May 18, 1998
For immediate release

For more information contact Bruce McIntosh at (847) 966-6200

Wind testing shows how concrete walls hold up in a tornado

Dramatic images of 2 x 4s strewn across the landscape in the wake of this spring’s tornadoes bring up the question: What role does construction play in tornado safety? Tests at Texas Tech show that wall construction can make a world of difference.

The most inherent danger to people and property during the high winds of tornadoes and hurricanes is the debris carried in the high winds. Flying at such intense velocity, wreckage can cut right through a building wall and endanger the people inside. Tests conducted by Texas Tech University’s Wind Engineering Research Center offer dramatic proof that concrete walls withstand flying debris from tornadoes and hurricanes—and outperform their wood and steel counterparts.

To duplicate tornado-like conditions in the laboratory, researchers shot wall sections with 15-pound 2 x 4 lumber "missiles" at up to 100 mph, simulating debris carried in a 250 mph wind. These conditions cover all but the most severe tornadoes. Hurricane wind speeds are less than the speeds modeled here. Missile testing designed to demonstrate damage from hurricanes use a 9-pound missile traveling about 34 mph.

Researchers tested 4 x 4-foot sections of concrete block, several types of insulating concrete forms, steel studs, and wood studs to rate performance in high winds. The sections were finished as they would be in a completed home: drywall, fiberglass batt insulation, plywood sheathing, and exterior finishes of vinyl siding, clay brick, or stucco.

All the concrete wall systems survived the tests with no structural damage. Lightweight steel and wood stud walls, however, offered little or no resistance to the "missile." The 2 x 4 ripped through them.

Reinforced concrete homes have proven their wind-resistance in the field during tornadoes and hurricanes. In Urbana, Illinois, a recently constructed insulating concrete form home withstood a 1996 tornado with minimal damage. In the Liberty City area of Miami, several homes built using the shotcrete technique survived Hurricane Andrew in 1992. In both cases, neighboring homes were destroyed.

"The results of the tests were not surprising, but they were dramatic," says Donn Thompson, PCA’s residential technology program manager. "Concrete walls meet both the criteria needed to protect occupants in a severe storm—structural integrity and missile shielding ability."

Seeing is believing. A new 8-minute video shows the wall tests, providing visual evidence of concrete’s resistance to wind-driven debris—the biggest threat to live and property in hurricanes and tornadoes. Copies of the video, Built-in Safety (VC511) are available from Portland Cement Association for $4.95 plus shipping and handling by calling 800/868-6733.

For information on building concrete homes, see the website <concretehomes.com> or call the concrete home hotline toll free at 888-333-4840. A trade association based in Skokie, Illinois, PCA conducts research, education, and public affairs work on behalf of its members—US and Canadian cement companies.