GULFPORT, MS (AP) A few more nails and extra bolts could have made a big difference for some homes that were blown away by Hurricane Katrina.
An initial engineering review found that most of the wood-frame houses that survived the storm’s 130 mph gusts held up because of little things — plenty of nails, metal straps attaching rafters to frames and bolts anchoring frames and porches to concrete. Often, the homes with the most damage simply weren’t built as well, inspections showed.
John van de Lindt, a Colorado State University professor who was part of a team that assessed storm damage, said the pattern showed up in approximately 100 different structures the group inspected at 30 locations in southern Mississippi and eastern Louisiana.
“The lesson to be learned is attention to detail,” said van de Lindt. “If the [building] code was followed, things seemed to do really well.”
The five-person research team organized by the University of Alabama spent three days visiting communities that were hit by Katrina in search of clues to help determine why some homes were okay after the storm and others were uninhabitable.
The team included university researchers, building-code specialists, engineers and officials from the wood industry.
The group — which will make recommendations for possible changes to the standards used in building codes — didn’t spend much time looking at the rubble of homes nearest the coast. Such structures were washed away by a storm surge and waves topping 35 ft.
“Designing against surge can be done, but it would be so expensive that no one could afford it,” said Andrew Graettinger, an associate professor of civil and environmental engineering at Alabama.
But just a little inland, researchers checked houses and found a pattern: Damage was most severe to homes where builders used too few nails or didn’t properly use metal straps to secure roofs, as outlined in building codes for hurricane-prone areas.
Dave Johnson, a building inspector in Harrison County, said most of the area’s coastal towns operate under a building code that requires that structures withstand winds up to 130 mph. Farther inland, buildings are rated to weather 100 mph winds, he said.
Johnson said code inspectors ensure there are only “very minor differences” in construction from one contractor to the next, but the research team found evidence of spotty quality.
“There definitely was, unfortunately, a difference from builder to builder,” said van de Lindt. Rather than purposely skirting building codes, builders apparently didn’t understand all the requirements of constructing hurricane-proof homes, the team believes.
New homes fared better than older ones, he said, but porches were a problem area.
“The columns supporting them were just resting on the concrete, and the wind would just pick it up,” said van de Lindt. “That led to roof failures on both homes and light industrial buildings.”
The Home Builders Association of Mississippi, a trade group with approximately 4,000 members, said it supports the adoption of a uniform statewide building code —currently lacking in the state — but it did not immediately respond to other questions about the damage review.
The states of Louisiana and Alabama already use codes published by the nonprofit International Code Council, which develops building guidelines used by many governments.
Nick Jones, an engineer who has studied the way wind flows around buildings during hurricanes, said the construction industry isn’t using all the techniques it could to reduce damage in storms like Katrina.
“This leads in most cases to the most spectacular and catastrophic failures, as it sounds like was the case here,” said Jones, dean of engineering at Johns Hopkins University in Baltimore.
Damage from the storm surge and waves extended as far as a half-mile inland in some areas, Graettinger said. Building houses on stilts isn’t the sole answer to protecting them from hurricanes since elevated homes are more susceptible to wind damage, he said.
“To design against this would require construction comparable to a bomb shelters, which, of course, can be built, but would be extremely expensive,” he said.
The research team’s work was funded by the National Science Foundation, which will use the findings along with the American Society of Civil Engineers to develop better standards for wood-frame structures.
The report is being completed and could be circulated within the industry within weeks, according to van de Lindt.
Gretchen Hesbacher, a spokeswoman of the International Code Council, said the 2006 rules are being prepared now, so any changes prompted by Katrina would appear in amendments published in 2007.
“Generally, lessons learned in a natural disaster show up in codes fairly quickly,” she said.