Impact of Hurricane Andrew: better homes
In the two decades since Andrew, Florida has beefed up building codes, but experts caution homes and buildings remain a long ways from storm-proof.
06/02/2012 5:00 AM
08/19/2014 7:04 PM
It’s a random concrete-block home under construction in a humble Miami neighborhood, but it captures an important legacy of Hurricane Andrew:
They don’t build them like they used to. And thank goodness for that.
In the two decades since Andrew splintered subdivisions from West Kendall to Homestead, beefed-up building codes have raised the odds homes will remain intact after the next major hurricane, but also raised their cost.
The changes go beyond impact windows and shutters. From roof decking to re-bar, the bones of the little box going up in Northwest Miami are thicker, stronger and “far superior” to flimsy homes that folded during Andrew, said Flavio Gomez, director of Miami-Dade County’s building department.
“I’d feel safe here in a hurricane,’’ Gomez said during a roofing inspection last week.
But for all the improvement, some engineers and disaster experts worry that builders and buyers now place too much faith in Florida’s vaunted hurricane codes. They also question a building code rollback outside of South Florida quietly approved last year.
“Built to code,” they stress, does not mean hurricane-proof — not even in Miami-Dade, Broward and Monroe counties, which maintain the nation’s strongest wind standards.
“The building code is the minimum requirement. You have no choice but to meet that by law but it doesn’t mean it’s the best or strongest design,” said Ricardo Alvarez, a Miami-based expert on structural vulnerabilities. “We should be building code-plus.’’
Yet the Florida Building Commission — a 26-member board of building industry representatives, architects, engineers and code officials appointed by the governor — signed off last year on a revised statewide building code that reduces wind standards for inland areas and the northern half of the state.
State’s southern tip
at higher risk
The latest version of the statewide code, which is updated every five years and took effect in March, shifts the state’s “wind-borne debris region” where shutters or impact windows are required. It adds a wide belt across inland South Florida, reflecting higher risks, but drops most of the Panhandle, the Big Bend region and the Jacksonville coast, which just weathered Tropical Storm Beryl.
The new code also recalculates “wind loads,” a critical measure of the wind pressure buildings are supposed to withstand, dropping them an average of 20 percent across much of the state. In inland Jacksonville, the pressure ratings fell 35 percent.
They rose slightly in only one place: coastal Miami-Dade and Broward.
Jack Glenn, director of technical services for the Florida Home Builders Association, defended the changes, saying they reflect standards set by the American Society of Civil Engineers based on an array of new research, product testing and risk modeling.
“Pressures have been lowered but we have done it because the science says we should,’’ said Glenn, who serves on the building commission’s hurricane research advisory council.
The data, Glenn said, suggest only the southern tip of the state is at high risk of a strike from another storm like Andrew, a 165 mph wrecking ball that killed dozens and racked up $25 billion in damage when it hit South Miami-Dade on Aug. 24, 1992. The highest wind ever recorded in Jacksonville, he said, was 80mph.
Another key factor was Hurricane Charley, which Glenn called the “ultimate test” of tougher standards the Florida Legislature enacted in 2002 after a decade of wrangling with the powerful development lobby.
After Charley hit the Southwest coast with 150 mph winds in 2005, damage surveys conducted by the University of Florida showed homes built under the 2002 code suffered far less damage than older ones. That made a case that “very conservative’’ standards could be rolled back in lower-risk zones, Glenn said.
“The general feeling was that in 2005 we were over-designing,’’ he said. “We needed to relax a bit because there is a cost impact.’’
Costs have always been a consideration in code calculations, said Glenn, with the aim of finding a prudent balance between structural integrity and affordability.
Generally, the higher the projected wind load, the higher the cost of construction. Depending on location, builders estimate wind codes add from 1 percent to 5 percent to home prices — thousands, even tens of thousands of dollars.
“We have to make structures that people will buy and live in,’’ Glenn said.
Though often misunderstood, building to code doesn’t mean designing for worst-case scenarios like a Category 5. Instead, the goal is to protect lives and minimize property losses from more likely risks.
The state’s wind-speed map, for instance, is based on a projected 3 percent chance that a region will be exposed to gusts of certain speeds at least once in 50 years. The wind speeds are key to the complex calculations of the winds loads or pressures that buildings are supposed to withstand.
For most homes and buildings, those speeds now range from 180 mph in the Lower Keys to 115 mph in inland North Florida, with Miami-Dade at 175 mph and Broward at 170 mph.
Tim Reinhold, vice president of engineering for the insurance-industry-supported Institute for Business and Home Safety in Tampa, which has long pressed for tougher hurricane codes, called the lowered wind loads “realistic’’ and said he didn’t expect them to result in substantially weaker building designs or materials. Standard products like roof shingles, he said, typically have safety margins 50 percent higher than they are rated.
“They’re backing off wind loads a bit,’’ he said, “but it’s probably not enough to really get you in trouble.’’
In Miami-Dade and Broward, building officials also see little effect, with impact windows and shutters already meeting new standards.
Still, some South Florida-based experts question why the rest of the state would accept relaxed standards, given the devastating lessons of Andrew, the nation’s most expensive natural disaster until Hurricane Katrina nearly drowned New Orleans in 2005.
Most of South Miami-Dade escaped Andrew’s worst winds, among the most intense on record. Engineering surveys and grand jury probes in the aftermath showed inadequate codes, worsened by shoddy workmanship and sloppy enforcement, contributed heavily to the damage.
Cheaper vs. safer:
The balancing act
Eugenio Santiago, Key Biscayne’s chief building official and longtime advocate of stricter standards, believes the bottom-line concerns of the building industry continue to exert too much influence in setting wind codes — at least outside of Miami-Dade.
“Unfortunately, this whole process has made me very skeptical. The thrust of their impact is to make construction cheaper so they can make more money out of it,’’ he said. “Unless we get a hurricane in Tallahassee, I don’t think it’s ever going to change.’’
Alvarez, the Miami building consultant and former deputy director of Florida International University’s hurricane research center, called builders’ bottom-line concerns shortsighted, arguing that beefier construction pays for itself in lower property losses when storms inevitably come.
“This whole argument that you can’t build stronger because it is too expensive is really not an issue,’’ Alvarez said.
As one small example, he pointed to a cheap upgrade called the “ring shank” nail, a hybrid of nail and screw. As an FIU researcher, Alvarez led a team that found that simply shifting from 8D common to 8D ring shank nails more than doubled the holding power of plywood roof sheathing — at about $15 more for a typical house.
Miami-Dade and Broward made ring shanks a requirement in 2005. But they didn’t make it into the latest statewide code, though more roofers outside South Florida have begun using them as a suggested option.
Despite the concerns, there is general consensus that Florida’s code has improved the safety of housing and public buildings since Andrew. New homes are stronger. To a lesser degree, so are many older homes that have been retrofitted, renovated or re-roofed.
In a survey of coastal states by the Institute for Business and Home Safety earlier this year, Florida’s hurricane codes and building inspections scored the highest marks.
“Florida has been the leader,’’ Reinhold said. “From a structural standpoint, it’s been a huge win wherever it’s in place.’’
The code has addressed major flaws exposed by Andrew and the storms that followed. In hurricane zones, there is more concrete and steel to anchor tie-beams that cracked and collapsed. Nails have replaced roof staples, which failed widely in Andrew but remain in common use in other Gulf Coast states. After roof tiles failed and air-conditioners busted loose during the string of hurricanes in 2004 and 2005, the building commission mandated stronger connections for both.
Manufacturers, resistant in the immediate aftermath of Andrew, also have dramatically upgraded products. Window standards established by Miami-Dade — surviving a strike from a nine-pound two-by-four fired at 34 mph — spawned an impact glass industry. Asphalt shingles, which once broke lose at 60 mph, now come rated to hold off winds as high as 150 mph.
Most experts agree the rules that Miami-Dade adopted two years after Andrew and has tweaked in the 20 years since remain the state’s gold standard. The rules, which Broward largely follows, are preserved in a special section of the statewide code designated as the state’s “high velocity wind zone.’’
Charles Danger, who oversees Miami-Dade’s permitting and environmental departments, said the county has had to fight pressure from “everybody and their brother’’ in the building industry to ease requirements.
Tom Lampert, Homestead’s building official, said oversight also sets Miami-Dade apart. The county is the only one in the state with structural engineers routinely checking and certifying building plans, he said.
“There are no more automatic signoffs from engineers who have never even seen the job,’’ Lampert said.
There are also differences in the nuts and bolts of the code: Every piece of what engineers call the “building envelope” has to be impact resistant, not just windows and doors but walls and roofs.
Roofing felt, or tar paper, is twice the weight required elsewhere. Plywood roof decking must be 5/8 of an inch thick at minimum, compared to a 1/2 inch on a home in Naples.
“It doesn’t sound like much, that additional 1/8 of an inch, but it make a big, big difference in resistance to uplift,’’ Alvarez said.
Still, some engineers see plenty of room for improvement.
The shattering of
Danger believes impact standards for high-rise windows, which shattered in buildings in downtown Fort Lauderdale and Miami during 2005’s Hurricane Wilma, remain highly suspect. Efforts to force owners to install upgraded glass were shot down, he said, and many buildings installed the same stuff that failed, though with stronger attachments.
“It’s crazy to have buildings on Brickell Avenue that, glazing-wise, are still subject to the same problems,’’ he said.
Builders and designers also have been slow to embrace promising new technologies, such as foams sprayed on the undersides of roofs to bond planks and seal out water.
Alvarez said that poured concrete roofs, which strengthen a home’s weakest point, are common in places like Mexico’s Yucatan peninsula but a rarity in South Florida.
If another major hurricane hits South Florida, Danger is hopeful owners of most post-Andrew homes would still have roofs. Homes likely wouldn’t escape unscathed, he said, but “my expectation is that you are still going to have a place to stay, to keep on going with your life.’’
Engineers and disaster experts caution that the tougher codes shouldn’t give anyone a false sense of security. Most homes in South Florida, for one thing, went up before Andrew. A major storm will still be a major disaster.
“We’re a hell of a lot smarter about what we build but the issue for South Florida is increased exposure since 1992,’’ said Richard Olson, director of extreme event research at FIU. “The number of people, the number of families, the amount of economic assets that are exposed to hurricane and storm surge has increased dramatically.
“I stand up in public all the time and say we’re going to get our asses kicked,’’ Olson said. “They say, ‘You’re trying to scare me.’ I say, ‘Well, yeah.’”
At that home in Northwest Miami, contractor Robinson Guzman said he builds with Andrew in mind. Guzman wasn’t in the home-building business when Andrew hit but saw the devastation firsthand during the clean-up — and it showed during a roof inspection.
“No shiners,’’ noted Pedro Estopiñan, the county’s roofing section supervisor, as he looked up at the decking. Those would be nails that missed trusses. “It’s basically over-code.’’
Guzman nailed roof decking every four inches, instead of the required six. He bought double wrapped hurricane straps instead of single.
He added four heavy steel “truss girders,’’ bolted through the concrete tie-beam, to anchor trusses at key pressure points.
All in all, he estimated he’ll put an extra $1,000 in code-plus material in a 1,300-square-foot home he said he’d already sold for $145,000.
“It’s actually a little insurance for me,’’ he said. “I know the owners are not going to have problems and that means I’m not going to have problems.’’
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