Study of hurricane damage and code
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Here is an article I saw on yahoo that shows the importance of understanding and following code. It is just bad for business and all of our reputations when buildings fall down and builders gets the blame because of bad building practices. Thought I’d pass it along.
Day
I don’t smoke, I don’t shoot smack
But I got a spicy monkey ridin’ on my back.
Don’t eat beignets, too much sugar and dough,
But I will play for gumbo
Yes, I will play for gumbo
-Jimmy Buffett
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Construction Played Role in Storm Damage
GULFPORT, Miss. – A few more nails and extra bolts could have made a big difference for some homes that were destroyed by Hurricane Katrina.
An initial engineering review found that most of the wood-frame houses that survived the storm’s 130 mph gusts held up because of little things: plenty of nails, metal straps attaching rafters to frames and bolts anchoring frames and porches to concrete.
The review was completed by a five-person team organized by the University of Alabama. University researchers, building code specialists, engineers and wood industry experts spent three days inspecting 30 locations in southern Mississippi and eastern Louisiana. The goal was to explain why some homes survived, and others were uninhabitable.
“The lesson to be learned is attention to detail,” said John van de Lindt, a Colorado State University professor who was part of the team. “If the (building) code was followed, things seemed to do really well.”
The group didn’t spend much time looking at the rubble of homes nearest the coast, where structures were washed away by a storm surge topping 35 feet. Instead, it focused on homes just a little inland.
“Designing against surge can be done, but it would be so expensive that no one could afford it,” said Andrew Graettinger, an associate professor of civil and environmental engineering at Alabama.
The research group determined that new homes fared better than older ones, but porches were a problem area.
“The columns supporting them were just resting on the concrete, and the wind would just pick it up,” van de Lindt said. “That led to roof failures on both homes and light industrial buildings.”
The group also found evidence of spotty quality between builders. But rather than purposely skirting building codes, builders apparently didn’t understand all the requirements of constructing hurricane-proof homes, the team believes.
Dave Johnson, a building inspector in Harrison County, said most of the area’s coastal towns operate under a building code that requires that structures withstand winds up to 130 mph. Farther inland, buildings are rated to weather 100 mph winds, he said.
Johnson said code inspectors ensure there are only “very minor differences” in construction from one contractor to the next.
The Home Builders Association of Mississippi, a trade group with about 4,000 members, said it supports adoption of a statewide building code, which Mississippi doesn’t have. The group did not respond to other questions about the damage review.
The
National Science Foundation funded the research, and will use the findings along with the American Society of Civil Engineers to develop better standards for wood-frame structures.
The report is being completed and could be circulated within the industry within weeks, according to van de Lindt.
Nick Jones, an engineer who has studied the way wind flows around buildings during hurricanes, said the construction industry isn’t using all the techniques it could to reduce damage in storms like Katrina.
“This leads in most cases to the most spectacular and catastrophic failures, as it sounds like was the case here,” said Jones, dean of engineering at Johns Hopkins University in Baltimore.
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Replies
This article says nothing we don't already know.
Every time the weather wipes out a bunch of homes, the damage inspectors find the same thing. Namely, well-built places did better than poorly built places, model codes saved homes when followed, and many homes were not constructed to existing codes. Nothing to see here, just move along.
A rarer, but more useful type of article is one that identifies previously accepted practices that were found to contribute to catastrophic failure. For example, stapled OSB roof decks that failed in hurricane Andrew. FHB had a great article after Andrew that profiled the lessons learned by how buildings failed. Perhaps Katrina can stimulate a similar article. Whaddya say, Taunton?
Bill
A bit old but the information is still, for the most part, valid.http://www.colorado.edu/hazards/wp/wp94/wp94.html#climateIt is all useful information but the meat of the matter, for building, is under the heading "DAMAGE MITIGATION DURING CONSTRUCTION"
about half way through the document. It includes considerable information arranged by section.
You are assuming that those who did the after event analysis made few or no mistakes and drew the correct conclusion.
It is very difficult to determine how a building failed. Much more difficult than your reference indicates. Certainly more material and fasteners makes a better house, but often a decoration - even gutters - added to a house will cause a well built house to fail.
The design of tornado safe rooms requires that the rest of the building to not be fastened to the safe room. If any of the building is attached to the safe room, the safe room fails.
I want to know who built this house on Rats Nest Road in Slidell.You get out of life what you put into it......minus taxes.
Marv
Someone who knew what the h*ll he was doing, and was obsessive about details.
It's also important that the house is up on lots of skinny sticks, therefore offering very little resistance to the storm surge. The same thing was found in the tsunami last December. Buildings that let the water pass through survived.
-- J.S.
Yeah, but I've recently seen pictures of dozens, if not hundreds, of sets of stilts with no house attached. And just keeping the roof on is a challenge, regardless of other issues.
With houses on pilings, they key is to ensure the pilings are in the ground far enough. If they aren't the storm surge and wave action erodes enough of the soil to cause the pilings to become unstable. JLC's sister rag Coastal Contractor had an article on this a few issues back.Jason Pharez Construction
Framing & Exterior Remodeling
I suspect that it's also important to make sure that the connection to the pilings is sufficiently strong. Likely many of those (now vanished) homes were just nailed, or maybe lag-bolted, but you really need straps running down the pilings a couple of feet or something equivalent. And the straps need to be tied to something on the top side that is in turn tied to the structure at multiple points, so that any uplift load is spread evenly.
With houses on pilings, they key is to ensure the pilings are in the ground far enough. If they aren't the storm surge and wave action erodes enough of the soil to cause the pilings to become unstable. JLC's sister rag Coastal Contractor had an article on this a few issues back.
I was once told that ideally you should go down as far as you go up. I don't know enough if there is any truth to that or not, or if its even possible-----------------------------------------------------------------------------
WWPD
Not necessarily....some of it depends on soil conditions....i.e., in one coastal community here, pilings have to be at a specific depth--no more, no less, or else they are in unstable soil.
On my father's house (which is subject to semiannual flooding but no storm surge), we set the pilings 5-5.5' in the ground, with about 8' above ground. We also rebar'd them into the 6" slab. The double 2x12 beams are bolted to the pilings, the floor joists are strapped to the beams, the walls have 9' OSB to go all the way to the bottom of the floor system, and the 2x8 rafters are strapped to the wall.
All this is a county in MS that has no official code or bldg. dept.Jason Pharez Construction
Framing & Exterior Remodeling
(Caution: I might be playing devil's advocate here.)
From the point of view of the (somewhat) logical homeowner, there is little advantage to ensuring that a house is built to better than minimal standards, part of the reason why such a small percentage of houses anywhere are well-constructed, even by those with the economical means to easily do it. Indeed, homeowners everywhere give their blessing to the builders (and bribes to the inspectors) to cut costs in areas not immediately visible.
After consulting with my insurance broker before construction of my own house to see if building better to resist wind/rain/fire/flood/storm damage would get me better insurance rates I found that the opposite was true. "Anything that increases the cost of building the house increases the cost to insure it" I was told. (Ontario, Canada.)They don't look at it that you are decreasing the probability of having to collect from them as a result of an insured damage. They look only at how much it would cost to replace it if a covered damage does occurr. But, of course, there are other considerations than insurance rates to take into account.
And as we all know, the vast majority of homes in North America don't qualify for the description "fine homes", and thus the economies of scale do apply more to sub-standard construction, making it all the more common.
Makes me wonder about that guy's house on the stilts. One scenario of the future- all of his neighbours will be in brand spanking new houses, and he'll be living in an older, storm-beaten house. Was it wise to build well? Maybe.
In my own case, I'm betting that it is. That is, if my NEIGHBOUR's roof doesn't blow off and land on my house!
-Brian.
You're forgetting that insurance rarely covers everything. The typical HO is left short $10-50K in most cases, even when insurance is adequate. Also, in our part of the country (tornado country) a home that holds together better has a definite safety advantage. (Of course, in hurricane country one has enough warning to evacuate.)
All of these posts had dwellings on them. Another survivor is pictured.You get out of life what you put into it......minus taxes.
Marv
You sure those weren't docks?
I am going to be in an area tomorrow that looks just like that, but the poles in the water used to be docks. Everyone there lost their dock and their bulkhead. Lots of damage to the homes from the storm surge, though.
I'll post pics when I get back with them.James DuHamel
He who dies with the most toys.... Still dies!
"For what will it profit a man if he gains the whole world, and loses his soul?" MARK 8:36
http://www.godsfreemusic.com
Hi Dan - Agreed - you don't have to remind me about the insurance racket. That shortfall usually doesn't exist when you're shopping for insurance, pay your premiums and buy your policy. But it CERTAINLY materializes from somewhere when it's time for them to payout. Grrrr. Don't get me started on the insurance companies now. I'm sure they're just as bad in the States as in Canada.
- Brian.
One thing that you are forgetting is that a lot of the requirements for building codes where already driven by the insurance companies.And in some areas where codes are lacking they have their own standards before they will insure a building.
Hi Bill - yah - actually that's one good thing. The rumour here is that the way they're going to get rid of all the old, polluting, non-EPA rated wood stoves and fireplaces in houses is through the insurance companies. They will ultimately just refuse to insure the house, initially in urban areas, unless the EPA rating is there.
I can't see many other ways of enforcing this without the insurance company's assistance. And, God knows - They just LOVE doing those kind of things to people for money.
And the insurance companies have done a lot for car safety with the IIHS and the NHTSA and their crashworthyness tests. FWIW I happen to drive a vehicle which they rated "one of the five safest cars of all time."
BTW- EPA rated stoves put out a whopping 1/10 the emissions of non- EPA rated stoves, and put out more heat into the home as well. Sorry, I digress a bit.
- Brian.
Re: "Indeed, homeowners everywhere give their blessing to the builders (and bribes to the inspectors) to cut costs in areas not immediately visible."Actually from what I have seen builders use tougher building codes to justify higher prices. If it raises the actual cost $100 they price it out at $1000. The difference lining their pockets and adding documentation to the ABCs lobbying efforts against tougher codes. Shortcuts don't usually benefit home buyer as the HO pays for the house as planned not as built. Only the builder benefits from cutting corners.In a capitalist society the buyer only gets what they pay for if they are either lucky and/or hold a gun to the builders head.
95 % of hurricane damage will be within the first couple miles from the coast. and then most of that will be because of the water. You really cannot defend against the water. Then away from the coast, you got the wind , whixch will effect trees and power poles. When they fall they cause damage. alot of wind in the last three storms at my house was high wind. which effect trees.
Several of the hurricanes to hit Florida about 10-15 years back caused extensive wind damage to homes. The homes would lose their roofs, or a wall would cave in, then that was all she wrote -- the rest of the home would pretty much just blow up. Post-mortems revealed that critical connections would fail such as gable end truss connections (the entire wall would pop out), windows (the entire window would blow out), or simply the roof truss-plate connections.As a result, Florida building codes were greatly strengthened. Of course, there have been complaints that this has resulted in even more corruption in the building trades, but that's a different issue.
Hi 4Lorn1 -
"Shortcuts don't usually benefit home buyer as the HO pays for the house as planned not as built. Only the builder benefits from cutting corners."
Oh oh. You let the cat out of the bag. (Read that facetiously.)
The homeowner gives the blessing to the builder when he takes the "low bid". The homeowner doesn't want to know the specifics - he just wants a house built cheap. The HO game is - whoever builds the cheapest house wins. Many HOs only stay in the house for a few years before moving on, and if the shortcuts aren't too obvious he can then sell the house for the price that a correctly built house would command, and pocket the difference.
A case in point. A house under construction about 300 feet from my house was built with no dovetail or rebar dowling set into the footings to tie them to the foundation. (They may have later drilled and epoxied rebars into it later after I was gone, but I doubt it- I wasn't there the whole time- and the poured foundation covers it all up.) The builder likely does this on a routine basis with his houses and can be more competitive in his bids as a result of it (and other things). The HO also sees a saving in the lower price he has to pay for the house. And if the backfilling is done carefully and the trucks stay away from the house it will never be detected.
Certainly the builder will oblige the HO by billing him less than he would charge to do the work "properly", but enough that his profit margin is at least the same.
It's unspoken around here (but accepted and expected) that the low bids are below minimum standards, and the higher bids will at least meet the minimum standards (eg. "Code"). But, the illusion is that the low bid will get you the minimum, and the other bids above that will get you higher standards, depending on how much you're willing to pay. I've visited construction sites where the low bid was not taken, and STILL minimum standards are not met in every aspect. The extra cost went to showy frills instead. It's what the HO wants.
Regards - Brian.
> I've visited construction sites where the low bid was not taken, and STILL minimum standards are not met ....
The first thing I had done on my place was a copper re-pipe. I went with the high bidder, and his crew showed up wearing the lowest bidder's tee shirts. The hardest part is finding out who to trust.
-- J.S.
Hi John -
Around here that's fairly common, tradesmen working to different levels of quality. Most of the builders around here don't (can't) keep all the tradesmen busy full-time. Maybe production builders and the bigger slap-dashers can, but the better "custom" builders only have a few tradesmen going full-time and dedicated solely to them. The other trades are subbed out, but always to the same companies. Having a few "known" key trademen provides some uniformity and control over the end product.
The builder I went with did have several full-time employees, and the other tradesmen he did use he used exclusively, but those tradesmen also worked for other builders, often to a different standard, which they readily admitted. They all new the details that my builder, George, wanted, and stuck to them, while saying "this is the way we do it for George, and this is the way we do it for all the other builders". This they freely told me whether they were aware at the time that they were talking to the HO (me) or not.
While my house was being built, when I could, I liked to take a bag lunch and sit around with the guys at lunch time and talk about that kind of stuff. Sometimes some of them wouldn't know I was the happy HO and just think I was just another tradesman on the site, and so would talk quite candidly. It was funny to sometimes hear about the quick-and-dirty shabby work that such-and-such builder wants them to do. Or about the builder in a sub-division in Welland where all the garages are vinyl siding over tar paper, no sheathing (yes, no sheathing), and the siding is attached directly to the studs. (That one's GOT to be a code violation!)
One specific example that comes to mind: the rocker normally uses a zip tool to cut all around the edges of the windows after the sheet is up for other builders, while George didn't allow it's use because it could compromise the integrity of the continuity of the vapour barrier by cutting it at that point. So the rocker had to fit the drywall without the zip cutter. Mind you, I don't believe these things are all code issues, but rather just good building practises.
But it must have been disconcerting to see those guys wearing the lowest bidder's tee shirts!
And yah - the TRUST thing. That's what it's really all about. It's not whether the GC can be trusted or not. It's about whether or not the GC can make the HO THINK he can be trusted. ; )
Regards - Brian.
> But it must have been disconcerting to see those guys wearing the lowest bidder's tee shirts!
Yup. Point is, I got the low bidder's job for the high bidder's price. An expensive first lesson.
-- J.S.
While there is no insurance cost advantage to building a better building, there is the hassle factor.If you do not need to spend time waiting for and doing repairs, you have time for other things. (You also keep more of your valued posesssions.)
I'm sure in some of the case there were homes that were built with inferior techniques. But really, you can't make and accross the board conclusion.
Last year my mom stayed in her house on Pine Island Florida (where Charley hit). It's a barrier island. She lives in a 10 yo manufactured home. The house next to her was destroyed, a brand new manufactured home 150' from that was 30% damaged and almost lifted off its anchors. My mom lost a few shingles and a rain gutter
There were block homes a mile one way and a mile the other that suffered more damage.
Storms, winds and what not are so unpredictable. -----------------------------------------------------------------------------
WWPD
"From the point of view of the (somewhat) logical homeowner, there is little advantage to ensuring that a house is built to better than minimal standards..."
Somewhat along your same line of thinking -
Someone here on BT once said thet they didn't WANT their house built any better than anyone else's house nearby. If it was, it might not get destroyed in a hurricane. (or whatever)
Then all the neighbors would get new houses and he'd be stuck with an old one.
T-shirt: A Team Effort Is A Lot Of People Doing What I Say
Thanks for the article, It sounds alot like the same things heard after hurricane Iniki and Iwa here in Hawaii. I was a kid during Iwa and early twenties during Iniki and I've seen houses i have worked on (Family is in the trades, third generation here) and built damn near identically and one is gone and the other sustained minor roof damage. Big factors the from a physics standpoint are the surface area of the side taking majority of the winds, orientation (i.e.diagonal to the winds), Gable vs hip and pitch of the roof, overhangs (24" vs 36") etc., Large shrubs absorb some debris and baffle wind, wide open flat yard or house in a slight depresion, retaining walls, cmu block walls or fences, neighbors next to you all have two story or bigger houses and yours is a low 4/12 hip. The list goes on...
Building code here is, well....unique, depends on the inspector and or the builder, you guys that have been around know.. some guys get leeway and some don't, ironically the guys that don't tend to overbuild to keep the -spectors happy.
Just some of my thoughts to provoke some juicy debate!
> here in Hawaii.....
Is there anything you do special because of the volcanoes? We have earthquake bolt down and shearwalling.
-- J.S.
I've been in and out of my office, but not long enough to sit here on breaktime..sorry for the delay. The code is mainly for the threat of hurricanes, similar to florida.Nothing for "liquid hot magma!" (in the voice of Dr. Evil in Austin Powers movie)
You a Calif. Bay area builder?I cut the board twice and its still too short ! ! !
> You a Calif. Bay area builder?
No, an owner-builder in Hollywood.
-- J.S.