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Concrete House Stands up to Katrina

The Sundbergs had been building their fully-mitigated home for eight years, and it was 85% complete, when Hurricane Katrina slammed into their area on Aug. 29 with a huge storm surge and reported sustained winds of 125 mph. The water reached an elevation of 28 feet.

After the winds had died down and the water retreated to the Gulf of Mexico, the Sundbergs found that their home had survived the storm largely intact, with some blown-out windows, lost materials and missing upstairs panels. Now they are focusing their efforts on finishing the building before the next storm strikes.

“This is where our heart is,” said Scott Sundberg, a graduate of the University of Alabama and a structural engineer for 25 years. He used his experience with structural physics and design to build the home, which he and his wife Caroline call Shadowlawn.

Before breaking ground, Sundberg did his homework. He studied the Federal Emergency Management Agency's (FEMA) Flood Insurance Rate Maps, Florida building codes and the storm history of the area, and he visited abandoned home sites where scars of Hurricane Camille were still visible. The information from his research motivated him to build the home to withstand severe storms.

In 1998, Hurricane Georges dealt a glancing blow to the Sundbergs’ area of Pass Christian in Harrison County, which is one of the three counties in Mississippi that was hardest hit by Katrina. When Georges hit, the Sundbergs had just put the forms up and rebar in place for the carport slab.

“I became even more convinced [after Georges] that it had to be right, that it had to withstand a Camille,” Sundberg said. Hurricane Camille was a Category 5 storm that raged across the Gulf Coast in 1969, leaving a wide swath of destruction.

A native of Thornton, Ill., where there is a major concrete quarry, Sundberg said that “concrete has been in my blood since I was young.” Accordingly, when it came to building his dream house, he used concrete as the main building material. The result is a sturdy house constructed of Insulated Concrete Form (ICF) walls, reinforced both horizontally and vertically; post tension concrete slab; concrete columns; and a concrete roof on top of cold rolled metal panel sections.

The Sundbergs’ house has spread footings, with concrete members to distribute the load to the soil, and a 4-foot-high beam-wall and a beam-wall down the center. There is connectivity through the house from the roof down to the third floor, on to the second floor, and then to the carport. The house is also built to “perform elastically’”and to withstand winds of between 180 and 200 mph. The bottom of the beam of the first floor living space is 25.4 feet above sea level, according to the National Geodetic Vertical Datum (NGVD).

The carport elevation of the Sundberg home is 14.8 feet, which is above a 14-foot base flood elevation (BFE) for the area. The slab-floor level of the house is the carport and it has a small interior room. This space had breakaway walls which “blew away perfectly,” said Sundberg.

The windows that were installed in the Sundberg home were vinyl gliders, which are not hurricane-resistant. The few windows that did blow out will be replaced and hurricane shutters installed as planned, adding another safety measure to the home.

Sundberg’s home also has a second floor area designed as a “safer” room, with walk-in closets sheathed in plywood and framed with six-inch 18 gauge metal studs at 12 inches on center. The room is not, however, a Safe Room per FEMA 320 Guidelines, which are recommended because they provide home owners with guidance to assess their tornado risk.

Sundberg firmly believes that adopting proper codes, with respect to the BFE, “could prevent 75% of the damage” from hurricanes. “As compliance increases, damage is less,” he added. Sundberg has been following the stronger codes that were put in place in Florida in the mid-1990s following Hurricane Andrew.

The Sundbergs’ home, which stands roughly 350 feet from the shoreline, is fully insured. The couple has yet to settle their flood insurance claim. They had renters insurance for the contents of their rental home in Long Beach, which was destroyed. Unfortunately, they did not have flood insurance, so they lost everything at that property, and their belongings and precious records were not insured against flood. The Sundbergs had to replace their cars, and all of the finished landscaping at their new home was destroyed.

Since Katrina, the couple has been living in an 8-foot by 33-foot trailer, with two 3-foot slideouts parked next to their driveway.

When they visited their new home after Katrina, Sundberg looked for cracking, spawling and displacement. He was relieved to find no signs that the structural integrity of the home was compromised. “Using concrete adds about 10% to 15% above the cost of conventional construction,” stated Sundberg. In this case, it proved to be a wise investment.

 


 

Plan to Attend the 2006 Concrete Tour

Concrete is among the fastest-growing building materials and one of the most essential. To learn more, plan to attend the 2006 Concrete Tour will be held in Phoenix on June 11-13. The tour offers completely new information and behind-the-scenes technologies.

 
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