Friday, April 20, 2012

The false dichotomy: Tornadoes and home construction

The widespread prevalence of mythology seems to characterize the whole subject of tornadoes and their interaction with humans.  For example, I recently wrote a blog about the myth of water tables preventing the construction of basements.  Someone recently passed on to me a "Disaster Safety Review" put out by the Insurance Institute for Business and Home Safety, that contains some fascinating material, that I'll address shortly.

However, the main issue compelling me to write this blog is a false dichotomy:  the builders and their lobbyists say that it's possible to build a tornado-proof home, but no one could afford it or even want it.  This argument presumes that the only two options available to a prospective homeowner are either (a) a tornado-proof bunker, or (b) the standard, flimsy frame home built in the USA.  That this is a false dichotomy should be evident to anyone who knows anything about construction.  It's quite possible to construct homes that would resist damage from tornadoes - that is, to some standard somewhere intermediate between (a) and (b).

As should be well-known, the hurricane-prone regions along the Gulf of Mexico and Atlantic coasts have building codes that mandate homes be built with more structural integrity than is required for homes in the rest of the nation.  Essentially, outside of the coastal zones, the standard is that the home be constructed to resist structural damage in winds up to 90 mph - this is option (b), above.  In the coastal zones, the standard is up to 125 mph!  Apparently the builders are quite capable of building homes to that higher standard (assuming it's actually enforced).  Note that this higher standard does not make homes either hurricane-proof, or tornado-proof!  Their enhanced structural integrity makes them hurricane/tornado-resistant, however. Such homes can be built and apparently they're affordable!

In even a violent tornado (EF4-5), the violent damage comprises only a small percentage of the damage path.  Therefore, by far the majority of the damage path area experiences winds of EF-3 or less (currently, the bounds of EF-3 are nominally 136-165 mph).  If we had all new homes built in the USA held to the higher standard applied in the hurricane-prone regions of the US, we eventually would have far less structural damage to homes, even in violent tornadoes!  In EF-2 and weaker tornadoes, structural damage would be nearly eliminated.  Reduced structural damage would provide reduced debris loads in tornadoes, and it's well known that debris within tornadic winds makes those winds considerably more destructive!

Of course, a lot of "legacy" homes will remain for a long time that were built to the lower standard (b).  Their structural damage would still contribute debris that could affect the damage even in well-constructed homes.  Airborne debris from your neighbor's flimsy home could "reach out" and harm your home, even if your home is well constructed.  I've seen examples of this in my damage surveys - it's not enough just to have your home well-constructed!  Whole neighborhoods and, eventually, whole communities need to be well-constructed to provide the optimum safety from unnecessary damage.  This problem can't be corrected overnight, obviously, but if we do nothing to enhance building codes within the tornado-prone areas of the USA (essentially everywhere east of the Continental Divide), then we'll be plagued indefinitely with what amounts to unnecessary damage from tornadoes.

I note that in the safety review mentioned above, the states of TX, MS, and AL are rated quite low in terms of building code and enforcement.  If one were to search for reasons why tornado outbreaks in "Dixie Alley" produce so many fatalities, this might be a good place to start!

1 comment:

Gilbert said...


Darn spot on. See: most people think that their new homes are built to modern U.S. standards established by the local, stae and federal governments and industry. But what they really are is MINIMUM REQUIREMENTS to make minimum code. Now, changing that code isn't terribly difficult, and I'm NOT suggesting we come up with a ton of new regulations and whatnot (or even any new ones!), but merely to change the ones in place to include a 125 MPH standard. Yes, they ARE more expensive, but not by much to the point where people notice them.

The problem, though, is that the homes already built will last 100 years or more (well, most of them, I hope) before they need to be bulldozed or abandoned. And if the latter, they become an even bigger problem, because they become dilapidated and easy to fly apart when even a weak tornado hits them. Of course, with abandoned barns or ones in poor shape all over the place where I live, I understand that too well!

And then there's the debris. If you surround your homes with trees, it's shady and homey, but then one flies into your house and even if it could withstand the straight-line wind, a tree will mess up your house very badly.
Landscaping needs to be coordinated in this as well!

Finally, I'd also like to point out that, in the city I live in, the code is such that the homes are required to have shingles (if it has them, which they usually do) that can withstand 60 MPH winds. Welllllll...(tm Chuck Doswell), we get that to occur in severe thunderstorms or even gradient winds roughly twice a year, on average, around here! And what do you think happens to them? Ahhh, yes. It's always fun around my subdivision after a good storm, seeing who the poor person was who will now have to deal with a mess.

But again, the discouraging thing is, it may take years to get this done, and another 100+ years before it's fully implemented in every home. I'm open to any ideas on how to speed that process up. In short, home construction in this country is largely subpar to the weather we experience in much of the country. There is a relatively "easy" fix on the rulebooks, it seems, but in practice and getting it across to lawmakers, welllll....

Gilbert Sebenste
Staff Meteorologist
Northern Illinois University