Around the Vista Park neighborhood of New Orleans, several houses are under repair or construction. Although I am disappointed that many people are simply repairing slab-on-grad houses without elevating, I have been encouraged to see construction of new homes at safer heights.
The majority of these new structures are modular homes. Typically these houses are placed on walls or piers about 3 feet above adjacent grade--the minimum height according to the advisory base flood elevation for our neighborhood. An improvement, yes, but I sure wouldn't recommend building so low. As long as you're building a new house, I say go as high as you can.
A handful of houses here have done just that, raising their living space 8 or more feet off the ground. Of course, doing so costs more and requires a much more detailed design.
One such house, just around the corner from our FEMA Travel Trailer, was ready to be lifted into place this weekend. The contractor had started from scratch, driving new timber piles and placing a brand new slab for the garage level. They had then formed up about two dozen square concrete columns arranged all along the perimeter and a row right down the middle.
Saturday morning I saw the two halves of the new modular house being trucked in and the large crane towering above the trees and wires ready to lift those pieces into place. We were headed out for the day and I was just a little disappointed that I would not be able to see the house come together.
Late Saturday afternoon we returned to see the crane folded up and ready to leave, but the modular house was still wrapped in plastic on the flatbed trailers. I went over to take a look and met the contractor, a lanky man with a north Louisiana country accent. He scowled when I asked what happened.
"No rebar," he said. "Barely two inches of it."
At first I did not understand what he meant, but then I looked again at the slab and columns and saw that the entire center row of concrete columns had fallen over!
The contractor told me that the first unit was being lowered into position when the columns gave way. They snapped off at the base, breaking cleanly where the cold joint of the column met the slab, each one pulling out the scant two inches of rebar that somebody foolishly thought would be enough to anchor these 9 to 10 feet tall columns.
Luckily no one was hurt as they collapsed like thousand-pound dominoes. Lucky still that this defect was exposed sooner rather than later. Had this house been completed on such poorly anchored columns the first stiff wind would probably pushed the house over to one side or the other, where it could have crushed a neighbor's house.
I've seen a lot of houses near here that have been elevated post-K, mostly pier houses that were lifted and then lowered onto columns constructed in place right under the elevated houses. I don't recall seeing shear walls or even cross bracing on any of them, so these houses rely on the strength of the connection at the base of the column to withstand rotation forces. Let's hope they hired somebody who knew what he or she was doing.
Of course the contractor in this case blamed his subcontractor for the ridiculously shoddy work, but he has every reason to be red-faced, too. He should have made sure that appropriate anchors were placed in the slab, and he should have inspected the columns to make sure the steel was tied together to provide a continuous load path from the anchor straps at the top of each column all the way into the foundation. To his credit, he told me he is going to fix it as quickly as possible at no charge to the owner, and sure enough equipment had arrived Monday to start cleaning up the mess.
The lesson is a good one: hire people who know what they are doing and check everything. Going tall is great for flood protection, but let's not forget that hurricanes pack a punch of wind, too. You don't need a degree in engineering to know that taller houses are going to catch more wind, but perhaps you do need an engineer to properly design for it.