• Hurricane Andrew

    Credit: NOAA

August 24th marked the 20th anniversary of the date that Hurricane Andrew made landfall on South Florida's Atlantic coast. The storm destroyed more than 65,000 structures; the aftermath would change the building industry in Florida, and indeed along the entire U.S. Atlantic and Gulf of Mexico coastlines.

Andrew "left a 25-mile-wide arc of battered homes, flooded streets and felled trees and power lines across the southern tip of Florida when it struck on Aug. 24, 1992, ripping away the state's pretenses of safety along with much of Miami-Dade's infrastructure," writes Jonathan Simmons on TCPalm.com ("Hurricane Andrew 20 years later: Everything changed," by Jonathan Simmons). "That storm, officials said, changed everything: from how homes are designed to how meteorologists track hurricanes and how the government manages emergencies."

A year after the storm, Don Best described the results of research into the catastrophe in a report for the Journal of Light Construction ("After the Storm: Hard-Won Lessons", by Don Best, JLC August 1993). Analysis by expert teams, Best reported, was coming into clear focus: "To a remarkable extent, the experts concur about the human and material failures that made Hurricane Andrew a much more costly disaster than it had to be. Equally important, there is a broad consensus forming on the steps that must be taken to forestall a similar disaster in the future."

Roofs were a key vulnerability, JLC reported. Perhaps 150,000 roofs had failed in the storm, including everything from asphalt to sheet metal and tile. Standards for roofing were inadequate across the industry: "In many cases, manufacturers weren't ever required to prove that their products could meet South Florida's wind loading requirements, or their products were simply rubber-stamped without any independent testing."

That has all changed, of course: Today, "Dade County compliant" is the gold standard for wind resistance of roofing materials, and building codes incorporate ASTM wind-resistance standards for roofing in high design wind speed zones in almost every coastal state.

Attachment of roof sheathing to roof structure was another key failure point, Best reported. "The most common cause of failure was that nails and staples were spaced too far apart, or missed the underlying truss completely. On some badly built roofs, fully half the sheathing nails missed the framing entirely." In the years following the disaster, Florida stepped up its enforcement of roof nailing.

Gable ends were another widely observed source of total building failure: when winds blew a wood-framed gable end in, the rest of the roof structure often blew off, followed by collapse of the walls. A year after the storm, the building industry was still working on a response; today, Florida building code calls for specific structural bracing details in residential roof framing — and even requires those details as a retrofit in the case of some roof covering replacements.

Window and door failures were another culprit. Wrote Best: "In literally thousands of homes, glass sliders, French doors, double-wide garage doors, and other types of doors and windows were blown out, frame and all, because they weren't properly secured to the framing." Today, Florida code, as well as code in high-wind coastal zones in other states, includes requirements for window and door attachment to framing, and for impact-resistant glazing or the equivalent opening protection for windows and doors.

But rules and requirements don't mean much if they're not enforced. And code enforcement in Andrew's strike zone had been notoriously lax. "Prior to Andrew, some building inspectors were writing up to 60 jobs a day (12 to 15 would be a more realistic rate) and some of those, it's been reported, were written in local bowling alleys and bars rather than at the construction site."

Today, Florida is known for strict and thorough building code enforcement. Earlier this year, the Institute for Building and Home Safety (IBHS), an insurance-industry funded research and education foundation, ranked Florida at the top of the Atlantic and Gulf Coast states in building code effectiveness ("Rating the States").

If a storm like Andrew were to hit the Florida coast this year, the improvements in codes, products, construction methods, and enforcement would help to limit the damage, experts agree. But Florida has grown in 20 years, and the state now has more to lose. So Andrew — like any other storm in history — would still cost more today than it did 20 years ago.

Karen Clark and Company, a Boston-based risk consulting firm, analyzed 20 historic storms and estimated what they would cost if they struck the same region this year ("Historical Hurricanes that Would Cause $10 Billion or More of Insured Losses Today"). "It's clear many hurricanes that struck the United States in the earlier part of the 20th century would cause orders of magnitude more damage today," said company CEO Karen Clark. "This is due not only to an increased density of structures in coastal regions, but also to changes in construction practices that have resulted in larger and more expensive buildings. Even a storm as recent as Hurricane Andrew, which struck 20 years ago this month, would be three times as costly today."