As reported by Mike Oliver of the Birmingham News:
On April 27, 62 tornadoes tore more than 1,000 miles of destruction across a state that has no statewide minimum building standard for houses.
The aftermath in Alabama — 250 dead and 23,000 houses damaged or destroyed — could have been greatly reduced with better construction, according to civil engineering and emergency management experts who have studied the damage.
Now, for the first time, the state is preparing to implement a statewide code for residential buildings as early as next month. But there is debate whether this new building code — which sets minimum standards for construction quality — will go far enough, and even whether it will be followed.
Although hailed as a major first step for a state that lags most other states in establishing a statewide minimum standard, the new building code might not apply in the dozens of counties and towns that have no code, unless those jurisdictions want it to apply. And it wouldn’t apply in those jurisdictions that have already adopted older, less stringent standards, unless they want to upgrade.
The proposed code contains no provisions for enforcement, and it exempts those local jurisdictions that adopted a code prior to March 2010.
“One very important thing is not only to have the code but to enforce the code,” said Harold Colon, an engineer with the Federal Emergency Management Agency and the supervisor of the hazard mitigation group which surveyed Alabama’s tornado damage. “If you have a code but no one is using it, it means nothing.”
Only 48 municipalities and seven counties in Alabama have enacted residential building codes, according to the latest International Code Council survey. The state has 67 counties and 440 municipalities, leaving most of Alabama’s small towns and rural areas without residential building standards. Alabama is one of 11 states without a statewide code.
Whether the new statewide code can be enforced in those jurisdictions without one is already being debated.
Several people on the 17-member Residential and Energy Code Board of Alabama, which is writing the statewide code and received the authority to implement it from the state Legislature in 2010, said those counties and municipalities that don’t have a building code will not be required to follow the statewide standards unless they choose to adopt a code. The statewide code would represent the minimum standards that those governments could adopt.
“If a local entity chooses not to do it, that’s a choice they make,” said Jimmy Brothers, who is the retired director of the Decatur building department and represents municipalities on the Residential and Energy Code Board. “If you do make a decision to do it, then this is what will be deemed a base code.”
But Jason Reid, regulatory affairs director with the Home Builders Association of Alabama, which played a large role in crafting the legislation that empowered the board, said the statewide code will be “the law of the land.” It could be enforced through the Home Builders Licensure Board, which could act on consumer or local official complaints and penalize builders with fines or license suspension.
Can lower damage
Regardless of the debate over the reach of a new code, the statewide standards, if followed, would better protect houses from damage by high winds, several experts said.
The state is basing its minimum standards on the 2009 International Residential Code with a few modifications, and it could be in place soon after an Oct. 6 public hearing.
The proposed statewide code requires houses to withstand winds of up to 90 mph except in coastal areas, where because of hurricanes the requirement ranges from 100 mph to 120 mph, depending on distance from the coast. Most jurisdictions in Alabama’s coastal areas have already established codes requiring those higher wind standards.
No practical code can save houses in a direct path of a major tornado — an EF-4 or EF-5 with winds ranging from 185 mph to well over 200 mph. The cost necessary to fortify against such high winds is impractical. And shelters and safe rooms are still the recommended method to protect lives in all tornado situations.
But several experts said the better construction that would accompany a mandated code would greatly reduce damage. That’s because historically 90 percent of tornadoes are less than 135 mph (EF-2 strength or less). And even with the big tornadoes, the majority of the damage is done by the outer bands of winds, which have lower speeds, experts say.
“The strip in a tornado where it’s the maximum wind speed is very narrow,” said Ernst Kiesling, a professor of civil engineering at Texas Tech University and an expert on the effects of wind on structures. “If you get a direct hit, of course, there’s considerable damage in that narrow zone. But the fact is the area is much broader, and most of the damage is done at wind speeds between 120 to 130. So if we can build a little above what the minimum code is, we could prevent a lot of damage.”
A study of Tuscaloosa’s tornado damage confirmed that more damage was done by the tornado’s weaker winds.
Although Tuscaloosa was hit April 27 by an EF-4 tornado packing top winds of 200 mph, the study, conducted in part by University of Alabama engineers, found that 92 percent of the damage to houses came from winds of 135 mph or lower.
The study suggests that better and relatively inexpensive construction techniques applied statewide could have saved or lessened the damage to the majority of the 23,553 houses that were destroyed or damaged on April 27.
Tuscaloosa currently has relatively up-todate residential building codes, but most of the damaged homes in the study were built before a code was in place.
Researchers wrote that more stringent codes for hurricanes have proved successful, especially against Category 3 winds of 130 mph or less, and should be considered for tornado-prone areas.
Incorporating some simple techniques used in hurricane-prone areas, coupled with housing inspections, “could significantly reduce damage and probably reduce fatalities,” said John van de Lindt, professor of engineering at the University of Alabama and one of the authors of the study published in July.
Other civil engineers and building experts reinforce the study’s findings.
Colon, the FEMA engineer, said the hazard mitigation team saw many houses — supposedly able to withstand 90 mph winds as called for in most building codes and in the proposed statewide code — that had collapsed in winds of less than that speed.
“We saw a lot of homes that shouldn’t be totaled, and we tried to find out why,” Colon said.
The answer: Lack of sufficient “connections,” Colon said.
That means methods for connecting the roof to the frame, and the floor to the foundation. With the roof more tightly secured, for example, the winds have to try to lift the entire house, now tightly connected, instead of just taking the roof and wreaking havoc.
“It doesn’t take much, and performance can be vastly increased with minimal cost when we pay attention to connections,” Kiesling said. “Connections of wall to floor and roof to wall. . . . In building failures, so often a portion of the roof is removed and then a lot of things can happen.” With weak connections, such as when only nails are holding the roof to the trusses, the rest of the structure is at much greater risk of falling apart and collapsing.
And when that happens, the debris becomes missiles that take aim at other houses. “It creates a chain reaction” of damage, with debris missiles causing more debris missiles, Colon said.
$600 cost
In Pratt City, homebuilder Stanford Smith is spending about $600 to make those connections on a house that will hold up against 120 mph winds, he said. FEMA workers visited one day last week to record the work for an instructional video.
“It seems like it would be complex, but there are some simple things to do so that it will perform better in higher winds,” said FEMA engineer James Crawford, watching Smith’s crew install the small metal connecting hardware — hurricane clips and straps — to “tie down” the house.
Other building techniques Smith touts include overlapping the plywood sheathing (or other types of building panels) on the walls and using more nails when securing board connections.
“Doing these things, you’ve got a stronger house,” said Smith, who works for Atlanta-based builder FD Moon & Company. “The wind wants to lift the house up and take the roof off, and I’m incorporating a system of redundancies to resist that.”
Smith said many builders could apply these techniques at little cost and easily exceed whatever code is in place. But he said few builders do it, and without regular inspections, they probably won’t.
Most codes require some kind of connections, although not to the hurricane standard. Regardless, tornado damage expert Tim Marshall said he saw lots of destroyed houses that had no connection from the foundation to the frame, resulting in the houses being easily pushed off the foundation.
Whether construction is improved through statewide code, local code, consumer demand or just improving awareness in the building community, the stronger connections make sense in the tornado-prone northern half of Alabama, said Marshall, a meteorologist and civil engineer with Haag Engineering in Texas.
“What they do down on the coast, they can do in northern Alabama,” he said. “Down there, there are houses that have gone through a lot of these hurricanes, and those houses survive.”
Not in state code
But that is not the case with Alabama’s upcoming statewide code.
Even with the 90 mph threshold of most residential building codes, including the one Alabama is set to adopt, hurricane-resistant techniques are not prescribed except in the coastal high wind zones.
Code board member Brothers said more study needs to be done before writing a statewide code that adopts hurricane standards and applies them to tornadoes.
“A lot of research and cost-benefit analysis needs to go into this before we say we can design houses in a cost-effective way to stand up to an EF-2 tornado,” Brothers said. “Because as soon as we say that, an EF-2 will come along and prove you wrong. Then we’ve built up false expectations.”
Brothers said the proposed statewide code establishes a minimum standard that addresses more frequent events such as straight-line winds from thunderstorms. In areas where they feel vulnerable to tornadoes, residents can enhance the minimum standards in their community, he said.
Reid, with the Home Builders Association, suggested that homeowners can use a new state law to fortify their house against wind and get an income tax deduction of $3,000 or 50 percent of costs, whichever is less.
In deciding how much to strengthen codes, states and communities must weigh the risk of being hit by a tornado against the cost of adding to construction requirements.
“The problem is typically that housing marketability is very sensitive to initial cost (of buying),” Kiesling said, “so anything you do to add to initial cost is resisted by builders and even the public because the public is uninformed of consequences and interested in size and amenities. So even homeowners might not be supportive of code changes if it does anything to raise initial costs. If we can convince the public to make a small, upfront investment, there would be a large long-term saving.”
Smith, the homebuilder, said codes are good as a starting point, but most are written with a lot of political influence from the industry and others — homebuilders, insurance groups, window and door manufacturers, even FEMA. Smith knows, because he once worked for the Engineered Wood Association (formerly the American Plywood Association) and participated in that influence.
“We did pretty well,” he said. “Builders want to reduce costs, product manufacturers want the codes to help increase their market.”
Reid said costs are an important consideration.
“When you look at an EF-4 and EF-5, it’s a rare event, and to say to build to a hurricane standard inland, well, that sounds fine, and if someone wants to they can. But the problem is you have to find the financing. Say you increase your house by $5,000 or $10,000 and the mortgage company has to approve and appraisers have to give you the value.”
Tim Reinhold, senior vice president for research for the Insurance Institute for Business and Home Safety, said his insurance- funded organization supports statewide minimum building codes, but because tornadoes are so rare, it’s hard to justify a hurricane-level code for an entire state.
“When it comes to tornadoes, the level of events and the rareness of them is such that it is outside the realm of what most people design for or look at. The chance that you are going to get hit by a tornado at any one point, even in Tornado Alley, is 1 in 5,000 years.”
Highest risk
Those numbers may be hard to accept, however, for many victims in Jefferson County, which has been rocked by killer tornadoes four times since 1956 — with some hitting the same communities, such as Pratt City, Concord, Pleasant Grove, North Smithfield, Edgewater and McDonald Chapel.
Much of Alabama, from Tuscaloosa to Birmingham and northward, is considered by FEMA as the highest risk, or “red zone,” for tornadoes. After April 27, Alabama became the top state in the nation for tornado deaths with 621 people killed since 1950.
Surveying the wreckage in Pleasant Grove after April 27, FEMA engineer Colon said he came upon a house that was standing between others that had been reduced to rubble.
He discovered that this homeowner had moved from Florida, where he learned about the use of hurricane clips and had insisted on spending the additional $500 or $600 for his Alabama house.
“The structure was still in place and the houses on the left and the right side were a pile of debris,” Colon said. “And they were exactly the same kind of houses.”
http://blog.al.com/spotnews/2011/09/alabama_tornadoes_some_experts.html
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