UF: Florida Building Code Revisions Improve Hurricane Protection

July 1, 2005

New Florida homes withstood last year's four hurricanes better than older homes, thanks in large measure to continued improvements in the state's hurricane building code, according to University of Florida (UF) engineers.

The engineers completed a study of how homes built before and after Florida's latest building code held up against hurricanes Charley, Frances, Jeanne and Ivan.

They concluded that homes built under the Florida Building Code that became effective in 2002 sustained less damage on average than homes built between 1994 and 2001 under the Standard Building Code.

Homes completed before 1994 fared worse.

A team led by Kurt Gurley, UF associate professor of civil engineering, compared 200 homes in the path of the highest wind zones generated by the hurricanes. The study did not formally include homes built before 1994, when the Standard Building Code's high wind standard became widely used in coastal areas. However, the researchers got a good idea of damage to pre-1994 homes as a result of their visits to storm-damaged neighborhoods.

The engineers interviewed homeowners, examined photos and other records of damage, and inspected homes for construction method, noting, for example, the size and spacing of nails used to affix roofing plywood to rafters.

Among the group's key findings were the positive impact of roof shingles. For example, shingle-roofed homes built under the 2002 code retained more asphalt shingles than homes built under the 1994 code. Retaining shingles is critical in hurricanes because loss of too many can compromise the roof, allowing rain to enter the attic and living space. The new code requires shingles rated to withstand higher winds than the previous code.

In Charlotte County, for example, nearly 30% of the surveyed homes built under the new code that faced Hurricane Charley's highest recorded wind gusts - as high as 150 mph - had no shingle damage. But every surveyed home built under the previous code experienced at least some shingle loss. Among those homes that did lose shingles, very few surveyed new homes experienced a loss of more than 10%. But 10% was the minimum for older homes, with many losing far higher percentages.

The benefits of the more rugged roof are clear in the study, but it's harder to determine the relative effects of code improvements from other issues such as aging, said Gurley.

The team found that a recent requirement for reinforced garage doors proved very effective. Most of the homes surveyed were built with this requirement, and none had significant garage door damage. However, researchers saw many pre-1994 homes whose weaker garage doors were blown off their tracks, a failure that often allowed wind to enter the house, damage the contents and attack the integrity of the roof from inside.

Despite the noticeable improvement in performance among new homes versus old homes, homes built under the newest code did not survive unscathed, Gurley said. Common failures among new homes include soffits, or vents located underneath roof overhangs to allow air to circulate through the attic. Wind sometimes damaged or blew out these soffits, allowing wind-driven rain to enter the attic, soaking insulation and even damaging ceilings and home contents in some cases. Gurley said improving soffit performance is one area (among others) the Florida Building Commission (FBC) will likely tackle in its next set of code revisions.

"The iterations and changes over the years to the codes Florida uses have made a measurable difference," said Gurley. The engineers, whose study was funded with a $90,000 grant from the FBC through the Florida Department of Community Affairs, presented their report at an FBC meeting in St. Petersburg.

A subcommittee will consider the study and other research and information to help steer recommendations for possible new code changes later this year.

The UF research is important because it demonstrates that quality codes are a key part of the prescription against hurricane damage, said Jeff Burton, building code manager at the Tampa-based Institute for Business & Home Safety, an insurance industry advocacy group whose engineering experts participated in the study. That's especially true outside Florida, already considered the nation's leader in wind protection codes, Burton said. "Comparatively speaking, there are other states that have no codes that have a high probability of a hurricane making landfall," he said. "In my line of work, I go to various states and try to educate them. Unless you have proof that they need codes, number one, and number two, that they actually work, it's a hard sell."

Source: University of Florida College of Engineering.