Hurricane thoughts

This may not have a lot to do with metal working but you guys are
smart and I thought I would ask. We are having out third hurricane in
a month and I was wondering. Has anyone ever thought about
retrofitting a house say, with a tie down system for an existing roof.
Maybe using steel cable tied into the foundation. I saw one trailer in
hurricane Charlie that survived just because it was properly tied down
and reinforced when all the others in the park were ripped apart. His
only damage came from the other trailers. I own several buildings in
South Florida that were built in the 1920 and would not like to see
them damaged if there was a way to prevent it. Any thoughts?
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The only thought I had while some people I knew went through Frances was building strom shutters out of metal. I have no idea if it would work, the thickness of metal you would need to use, design or even how you would mount them to the building. Ken
Reply to
Ken Vale
Anchoring might help a mobile home because the roof and siding are applied in large sheets but I don't know about older conventional construction. I helped with some cleanup after Hugo. It looked like things came apart in pieces.
Reply to
Glenn Ashmore
I do know what I've seen down at a navy base at Panama City, FL. They had a number of equipment shacks which had steel cables placed over the roofs, and the cables were tied off to large (one cubic yard or so) concrete Mafia blocks at the ends. I think the idea there was that the entire shack or trailer might become airborn and damage other structures.
Doing this with a large home would require some calculations of the forces involved so a suitable mass might be chosen, and the load spread out over a large enough area on the roof.
Reply to
jim rozen
I've seen a tornado resistant construction recommendation sheet. Its for during the home's construction, but it could be done after.
The idea is to tie each piece down to the foundation. It starts with extra stud bolts from the concrete into the sill plate. Then the framing walls have joist hangers top and bottom plus nailing instead of just nailing the wall together. Ring shank nails called for throughout. Extra nailing to the sill plate.
Sheeting on the side wall is to be 1/2 in plywood instead of built-rite. The bottom sheet goes past the foundation/sill plate divide and is concrete nailed to the foundation. I believe this sheet is pressure treated. Or maybe its nailed on to a pressure treated piece that's nailed to the concrete.
I remember the most important part was a special metal hanger to tie the rafter-truss to the top plate. Also extra metal pieces at the joints on the trusses. Ring shank nails were speced for the plywood sheeting in the roof.
I seen pics of this technique taking an F4 tornado. All the windows were blown out and the shingles were gone. A couple of 2x4s had pierced the walls. But the house was the only one standing on the block. FYI, an F3 tornado is equal to a Cat 5 hurricane. Of course, the tornado is at most a mile wide. Ivan looks to be a bit bigger.
Reply to
Karl Townsend
That COULD work, but if you have access to your attic, I would first apply hurricane ties everywhere and add diagonal bracing at the gable ends so that your rafters can't rack over. After hurricane Andrew, I saw house after house that failed at the gable end, something that is easily reinforced with a few diagonal 2 by 4's. Hurricane ties are just thick sheet metal that are used to tie your studs to your lower plate and then the rafters to your studs. If the plate is not already bolted to the slab/foundation, you have work to do.
Reply to
This story may be apocryphal, but it may well be true. Supposedly, there was one house that survived a direct hit from Hurricane Andrew (category 5) back in 1992. The guy that owned it worked for Ace hardware, and had glued and screwed every wooden joint in his house.
So you may be on the right track. If you can fasten your building down and to itself, it may survive. There are also some retrofit metal clips called "hurricane clips" that are for rafter tie-down.
Reply to
Jedd Haas
There is an area near here in Nova Scotia(Canada) that due to the geography funnels the winds throught a valley and reaches hurricane speeds. My mother comes from this area and remembers many of the houses with ropes and chains over the roofs and anchored into the bedrock. The houses are still there, so I guess it works :-) I have also heard of a place in Newfoundland call Wreck House, They say the winds are so strong that they will blow trains off of the tracks, and I have seen pictures of semi-trailers a hundred yards off the road after being rolled into the fields by the winds.
jim rozen wrote:
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An anchored fishing net would keep the roofing from lifting off, but it won't keep the walls from racking and the house disassembling itself at the joints. Houses come apart at nailed joints. The trick is to reinforce the joints with bolted through triangular plates, added diagnonal bracing, etc.
A car can go 150 MPH without pieces blowing off. That's because it is bolted together. Bolts, bolts, bolts. Nails pull out.
Reply to
Gary Coffman
Back in the 70's I lived on the Gulf Coast (Perdido beach area) and had the opportunity to ride Hurricane Fredrick out. It literally tore my gulf view house apart. I rebuilt it myself and was determined to make it hurricane proof. I poured concrete cubes of 1 cubic yard each every 10 feet along the house foundation. I used all hurricane clips, and out of the concrete cubes I had imbedded eyebolts that had steel cable that ran up the wall under the plywood siding, but up against doubled and tripled studds in the wall, over the roof decking, (used 2 1/2 inch x 6" tongue and groove for decking and finished ceiling,) with insulation on top of the outside of that decking), and attached the cable to cube on opposite side to a forged turnbuckle. So once cable was installed you could only see it where it exited the siding and attached to the concrete cubes. This house ha d a65 foot wide by 14 foot deep front porch rasied up to greound level overlooking the gulf from a bluff area. It was a half foundation as it was built into the natural bank on the bluff, so the porch was about 10 feet off the basements floor elevation. The entire front of the house was sliding glass doors and glass windows that opend up onto the porch.....and I had plywood all cut and prefit to cover it all up if need be and sotred in the basement.
I used 1/4 x 6 x 6 angles all embeded between and through bolted to attach triple 2 x 6's used to frame in the open front porch, instead of the double 2 x 4 I had used previously. The other side of the abngles were through bolted into roof and floor joists, and all joist and rafters where they attached were doubled or tripled, and reinforcing plates made of 1/4" plate was used. Triple nailed the plywood siding down and also used adhesive. Same thing for the exposed tonge and groove porch flooring and decks......all spiral twist nails and adhesives. I kept overhang on the roofs to a bare minimum, and cleared any remaining pine trees from the imediate area. As far as I know its stil standing after the last couple that hit that area, but it did get windows broke and internal damages as the new owner never boarded them up, and all it takes is one broken window and the house gets over pressurized and things start to bust. Do;t now if it buckled walls or roof, but I did what could be done to make it as bullet proof as possible back then........and most folks back then told me I was going overboard. I did utilize a heap of steel and carraige and through bolts etc in its reconstruction, as well as quite a bit of concrete. Visit my website:
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You aren't going to be able to do much now, with Ivan only a few days out. About all you could do now is to get a utility line crew to install power-driven earth auger anchors (BIG eye-bolts into the dirt) on both sides of the house, and run steel strand over the roof to tie it down - but all the utility line crews in the state are going to be plenty busy cleaning up from the last two hurricanes and bracing for the next one.
But when you build (or rebuild) the best way is to consider the local state and national building codes as a nice starting point, rather than "if we do it to code that's plenty."
Big foundation, over-strong wall and roof construction, bolt the house to the foundation every two feet or less, and tie it all together every which way from Sunday. Use 3/4" CDX plywood when they call for 1/2" OSB 'chipboard' for wall shear paneling or roof sheathing. Study the Simpson Strong-Tie catalog and use reinforcing straps and clips everywhere you can. Pressure blocking between all the rafters and trusses, lots of cross-bracing, lots of nailed down "rat run" planking in the attic, etc. Use wood glue or construction adhesive everywhere wood touches wood.
And someone already brought up pre-cut and stored boarding up materials. And design the walls with trim boards around the windows that are lag-bolted to the studs and ready to nail the board-up panels to. If you want overkill, build in rolling shutters that you can drop in minutes.
Reply to
Bruce L. Bergman
IIRC "Fine Homebuilding" did a couple of articles on hurricane damage after Andrew. The conclusion from the studies of destroyed houses was that the major point of failure was the roof separating from the frame and that this could be mitigated with steel reinforcing plates on the structure.
Reply to
Rick Cook
Yes, the building codes now require such a mass of plates and nails that the mass itself holds the roof down. Had to buy a palm nailer to build my sister-in-law's addition.
Reply to
Richard J Kinch
Up north you design a roof for positive snow loads. In florida you design the roof for a negative load. All the trusses and roof joists must be strapped to the headers and the headers everything tied to the foundation so it won't blow away in a 150 mph wind.
Shingles are not the best construcition in florida. Most of the older homes had Bahama roofe, The ones with the big flat stones on them to hold em down.
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I hitchhiked thru there around 1976 on the way from Port aux Basques to St Anthony to catch the boat to Labrador. The old timer I was riding with told me the same story about traincars blowing off the tracks, and there were indeed signs alongside the road warning of the winds.
Re chained down houses, one of the oldest buildings on the summit of Mt Washington has two large chains looped over the roof and anchored in the bedrock.
Ned Simmons
Reply to
Ned Simmons
All these comments are nice, but you, as a group, don't seem to realize a couple of facts. Florida has stronger building codes than either the national or the southern codes, and they are about to upgrade them again. Hurricanes are only one problem facing buildings in Florida. The major problem is termites. Most newer homes in Florida are CBS construction. CBS is concrete block stucco. I have never seen a concrete block or a CBS home with major hurricane damage. What I have seen is major bias in the media. In a recent newspaper there were accounts of several buildings being flattened by a hurricane. A church, an auditorium, and etc. But what made the photo section? Mobile homes directly in the path. I recently worked a demolition job at Kissimmee airport. Two steel hangars had failed. One was completely flattened and the other lost one end and required two cranes to support it as the expensive Lear jets were removed. (I can only wonder why they weren't flown to safety.) The apron was scattered with small planes with tail sections torn off. None of this made the paper, as far as I know. But the mobile homes did. If mobile homes are such death traps, why are they legal? And more importantly, where do all these older mobile homes come from? Florida is inundated with them. Seems like they should have all blown away by now. If your only information comes from the media, you have no idea what the truth is on most any subject.
Ron Thompson On the Beautiful Florida Space Coast, right beside the Kennedy Space Center, USA
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The ultimate result of shielding men from the effects of folly is to fill the world with fools. --Herbert Spencer, English Philosopher (1820-1903)
Reply to
Ron Thompson
Another post-Andrew apocryphal story is that the Habitat for Humanity homes were the only ones left standing on some blocks. This is supposed to be because there were lots of volunteers working on the homes, with lots of time to drive lots of nails. Plus they use 16 inch stud centers. I hope it's true.
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Reply to
Dave Wilson
And the homes were built to a higher spec as well. Typically, homes built by a builder for themselves or by large teams like Building trades in schools, Habitat... have more steel, tighter fitting this and that.
Some think they are lower quality, but only the test of time will prove it out. Some have.
Reply to
Martin H. Eastburn

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