Ok so now we have all the flood zones for years, and also all the minimum elvation first floor elevation heigths – say like 8 or 10 ft in parts of coastal south carolina, – but has there been any proof or real world experience about how well these new homes stand up to floods?
Sure they will be much better than one build 3 ft off the ground, but how does an 8 ft high in the air house in flood zones AE or VE stand up to a storm flood? Should you put your “stuff” in one of these homes, even tho built up, and risk it?
Edited 9/9/2008 8:59 pm ET by edwardh1
Edited 9/10/2008 7:30 am ET by edwardh1
Replies
Keep your eye on the pictures from Corpus Christie Texas this weekend and you can see.
Good idea.
Anyone else live in a storm area where these have been built, and had anothr storm?
No experience. I imagine it is not the flooding that will be the issue w/ houses on stilts ... it will be the storm surge that will test your structure! An engineer might be worth every penny of fee to build a good house on stilts.
If they are built well they stand up just fine. Hurricane Gracie hit Folly Beach with 140 mph winds in 1959. It washed away roads and a big chunk of the south end beach. For years after that there were 3 or 4 piling houses that sat out 100 feet or more off the beach. New technology and engineering makes them even better today.
The few I saw in Biloxi had very sturdily built "stilts", generally in the form of a reenforced concrete structure that doubles as a garage and storage area. These weren't right on the beach but inland a few blocks, so they wouldn't be seriously exposed to wave action -- the only real issue would be whether they're built up high enough for the worst-case storm surge. Of course, hurricane shutters, etc, are still needed.
Since it costs $50-100K or so additional to build up a house like this, I suspect most who can afford it at all aren't likely to cut corners on the structure, even if inspections are fairly lax.
I worked on one after Ivan. Right on the GOM Everything under the joists destroyed, slab all "blowout wall" and entry destroyed. Flood insurance only paid for lowest structrural member.
All the treated wood piles had been wrapped with T-111. If that wasn't gone it had been filled with sand. We cut holes in them, vacumed the sand and wrapped a second layer. No structural damage.
"Since it costs $50-100K or so additional to build up a house like this"
Maybe in MN, certainly not in Florida. In some cases piling houses are cheaper than slab on grade houses. The last house I built I paid over $30,000.00 for fill dirt just to build the house pad up to the required level. According to my engineer after 3 feet of fill pilings become cheaper.
That figure was for elevating the house, vs leaving it more or less on level ground.
There is no absurdity that human beings will not resort to in order to defend another absurdity. -- Cicero
You can't build any other way. You need your FEMA certificate at tie beam (why that is not at slab is beyond me)
You can build the other way in NO. Just gotta claim that the house wasn't 50% destroyed. (Never mind that it burned to the ground.)
There is no absurdity that human beings will not resort to in order to defend another absurdity. -- Cicero
The Florida building departments are very diligent about that 50% thing. If there is any question, you are building to FEMA elevation. All new additions and repairs are built to current code.
Yeah, well the rules are different in NO.
There is no absurdity that human beings will not resort to in order to defend another absurdity. -- Cicero
There don't seem to be any rules in New Orleans or they would have condemned and scraped most of the city. The right fix is to barge in enough dirt to get them to FEMA. Sure it would be expensive but what do you figure the next flood will cost.
It still wouldn't matter, it just doesn't cost anywhere near your estimate. Besides, we have no choice in the matter since it's mandated by federal flood insurance.
Watching This Old House several weeks ago I heard a New Orleans Habitat super say that elevating the houses they are building cost about $30,000.00 per house. That was with 35' pilings under a grade beam and with block stem walls up to about 5'.
Edited 9/13/2008 8:22 pm ET by florida
if nawlin force everybody to build to code, the crowd would move out of the city to high ground; problem solved.
I think it would be good idea in these areas to build the first floor out of poured concrete. Or reinforced block. Either way, make the first story bullet proof.
Like a basement, but above ground.
Then, right behind the front door have wide concrete steps going up to the second floor.
That way when it floods it would be easier to get all your stuff upstairs.
first floor- actually they try to make it breakaway so the surge can take it- just the opposite of what you suggest
katrina hit Biloxi at elevation 19
So what is the flood zone requirement?That is the question!
are you building to a ten year flood plan or the hundred year plus?
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Ya, I thought of that. I just can't get around not using that space. Maybe for an area where there is less potential for large surges. I saw a lot of homes in Katrina that were just flooded.
I built a home in a flood zone in nh. There are strict reqirements about how they must be constructed to deal with th water. Mine has 4 feet of concrete coming out of the ground. That puts the top of the concrete 1" above the highest recorded flood elevation. I could have framed the first floor there. Instead I went up another four feet and use the lower level for shop/garage space. There are vents in the foudation that allow a certain minimum flow in and out to prevent hydraulic pressures.
Flood conditions are only likely a couple times a year where I am and I have everything set up so I can raise all my machines up over 2 ft (putting the lowest portion of the machine that is susceptible to flood damage around 3 or 3 1/2 feet off the floor. It's a risk but I knew that going in. Worst I have had so far is 6" of water above the top of the slab. Zero damage and didn't lose so much as a piece of scrap wood.
Dried out remarkably fast in there too. No issues with mold or mildew. All mechanical systmes are mounted above the level of the concrete.
Breakaway panels are another way to deal with it.
My brother is in a raised house on the north shore of Lake Ponchartrain in Louisiana, one lot from the beach. His slab is 8 feet above sea level and his first floor is 17 feet above sea level. They park their cars on the slab, which is basically under the house.
It works fine.
I just got an email from him and he says he has more water under his house right now than he got in Gustav and Rita (he evacuated for those two because of the wind, but there was no evacuation order for Ike). In Katrina I think he got about 6 feet above the slab. He lost a few things and moved the HVAC compressor to a platform up high at the first floor level.
Of course a big part of the design is strapping and ties to prevent wind uplift under the house.
Billy
Just remember that no place in the U.S. appears immune from eathquakes and any elevating structures need to be designed with that in mind. In some areas, earthquakes may only hit every couple of centuries, but the earthquake folks are finding more and more areas with potentially strong quakes. There might also be the potential for a tsunami in many coastal areas which could create water flows far in excess of those of hurricanes. Not aware of any research on tsunamis in the Atlantic, however.
There was a program on TV about the potential for Atlantic Tsunamiis. I think sourced in the Azores, there is a strong liklihood that 'someday' they could have an earthquake/slide that causes a 90' tall tsunami to hit the eastern seaboard.Whew! My place is at 88';)
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I know a guy thats moving to 100' because you need to be that high after the polar ice melts.
That strapping is not there just for wind uplift, but so the house doesn't float away and bump into the neighbor's place like bumpercars on the beach.Does he have a high place to park the cars?
Or just snorkles for them?
;)
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Trade the car in for a Hydra Spyder:http://www.mobilewhack.com/reviews/2006_cami_hydra_spyder.html
He parked the cars a couple of blocks from the water and they were OK. The kayak came in handy when he had to take the dog for a "walk."
Billy
One of the basics of flood zone regs is that the first floor of living space is to be elevated one foot above flood level.
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I lifted my house, 120 years old, from 1 foot below flood elevation to 2 feet above. This is on the Jersey coast, one block from the ocean. Discussions about your stuff surviving a storm is secondary, in my opinion, to the insurance savings. My flood insurance dropped from 1800 to 400 per year. That's an every year thing as opposed to the every 100 year flood.
we'll know more about those answers after the reports are all in on this one.
But a portion of your premise is off, and seems based on assumption.
The regs are more for preserving lives than protecting property. That is secondary.
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