Florida Wind Codes Receive Scrutiny

New Florida Codes Bring Mixed Success, ENR August 23, 2004, reports on the aftermath of Hurricane Charley's passage over central Florida on Friday, August 13. Of particular interest are performance differences, if any, to be found between structures built before and after the mid-1990s, when substantial changes were made to Florida's building code wind design provisions in the aftermath of 1992's Hurricane Andrew.

The Turner Agri-Civic Center, designed to withstand 140-mph winds, collapsed in winds estimated at 100 to 110 mph.

Noteworthy points include:

• Wind speeds of up to 145 mph were recorded during Hurricane Charley.
• Mobile homes, designed to withstand 110-mph winds suffered significant damage.
• Charlotte County's three hospitals, all built before mid-1990 code revisions sustained damage. One hospital had to relocate 50 patients.
• Of perhaps even greater concern was the collapse of the Turner Agri-Civic Center in Arcadia. This two-year-old building was built to serve as a storm shelter and was designed to withstand 140-mph winds. However it collapsed under winds estimated at 100 to 110 mph. Over a thousand people in the shelter at the time safely evacuated prior to the collapse.
• In Punta County, every school except one suffered extensive damage. The exception, Sallie Jones Elementary School, was a two-story, tilt-up concrete structure with metal roof, and steel floor and roof framing. The school was designed to meet 2001 standards, including a 120-mph wind load. With an additional importance factor of 1.15, the effective design wind load was 138 mph.

Florida Changes Building Codes Between Storms, ENR September 9, 2004, reports on the Florida Building Commission's adoption of the International Building Code and a last minute amendment change to prevent a "loophole" in the new code that would relax wind design standards for a significant portion of the state.

According to the article, the International Code permits conventional construction in geographic areas with design wind speeds of 110 mph or less, whereas the existing Florida building code permits such conventional methods only in areas with design wind speeds below 100 mph. [Author's note, see International Residential Code R301.2.1.1 Design Criteria]. If left unchanged, the new code would have permitted approximately a quarter of the state to revert to conventional construction techniques not permitted for the last 10 years. As modified, conventional construction (e.g., no hurricane straps, no masonry reinforcing) is permitted in areas with design wind speeds less than 100 mph.

This article also makes some interesting observations regarding the effects of Hurricane Charley. For example, the hurricane destroyed approximately 10,000 homes and damaged another 16,000. But according to this article, all but a few of the destroyed homes were built to pre-2000 design standards.