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Nick32
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# Posted: 7 Sep 2012 01:14pm
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Forgot with the recent drough of tornado risk. Started working on my cabin, and since it sits in the middle of the woods with no safe shelter for miles...figure I better build one. Looking for a quick, cheap build that will last a few years, until I have the time to do a proper concrete shelter. So, thinking a 6x'6x'7' PT framed building, and just dropping that into a large deep hole. Then backfilling around the building with the dirt, and putting about a foot of dirt on top. I will have a center wall to support for the 1" plywood ceiling. Will that be stong enough to hold the dirt? I will use tyvek on the building to help seal, and it will sit on a gravel pad. Would something like this last around 3-5 years? Would this even work? Any feedback would be great. Anyone else ever build a simple, quick tornado shelter?
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MtnDon
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# Posted: 7 Sep 2012 01:23pm
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I've never built a buried shelter. However, that seems to be a pretty good idea as long as there is no danger of it flooding or having problems with a high water table. You'd want to know how much the wet dirt on top of the structure would weigh per square foot. Then calculate the required size of the roof supports, just like calculating rafter size for snow load. Also snow in case there is much of that although I think wet dirt would weigh more than the heaviest snow.
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GomerPile
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# Posted: 7 Sep 2012 01:35pm
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I was looking to build a root cellar and had a look at a neighbors (8x8x6 tall). He dug a hole in a hillside and used concrete blocks for the walls. His roof is made from railroad ties laid over a PT plywood ceiling. He used pond liner material to cover the area for about 10ft in all directions and covered with dirt. I would be ok hiding in it during a tornado.
Said it was a lot of cement mixing but pretty cheap overall.
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VTweekender
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# Posted: 7 Sep 2012 05:02pm - Edited by: VTweekender
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Here is what you don't want to happen with your design....you don't want a tornado to hit directly over it because it would certainly remove that loose one foot of dirt and suck what is inside right up into the tornado....you would want maybe steel beams on top with those secured into the ground from below the structure up to the beams with more steel and with cement footings...even if it took the dirt and plywood away, in this case the beams could save you if they are close enough together like 12" .....
if you don't take a direct hit then I would think you would be safe with the design
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adakseabee
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# Posted: 7 Sep 2012 11:25pm
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You should also have adequate structural support for the four sides of your building to resist the pressure of the surrounding soil to cave in the sides. If I were you I'd consult with a structural engineer. Better to be safe than sorry.
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MtnDon
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# Posted: 8 Sep 2012 12:27am
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Build the buried walls like is done with a permanent wood foundation. You can Google that. If it is not supporting a house you can probably not do all the detail work with crushed stone under the PT wood footings. PWF use a different grade of wood than what the local stores and yards carry. And yes, a direct hit might be bad news, but there are many times something like this would be a very good thing to have. The permanent ones I really like are constructed of welded steel and sit above ground. They are anchored into a huge mass of concrete all done in a single pour. Something like 18 inches thick, IIRC. They're usually placed inside another structure and none of the other structure is attached to the safe room. That can be found via Google as well.
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sparky1
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# Posted: 8 Sep 2012 09:20am
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Tornado Shelter in the middle of the woods ? trees falling Trapping you inside, Why not Bury a (plastic) or what ever they are made of, Water tank/Septic type tank,They are VERY strong and should survive,(my 2 Cents) & you wouldn't have to worry about water intrusion thru the dirt.I have never seen a tornado suck one out of the ground-but some Tornado's do pull Asphalt off of highways,
I have a friend burried a 10,000 Gal.(NEW) fuel tank-has bunks,12 volt light,"gel cell" battery, solar panel,keeps it charged,emergency supplies, BUT not near trees,that could Pin him in it.he's been in it 10 plus times last 6 years---Yes,southern Va.
sparky1.in southern va.
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Nick32
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# Posted: 8 Sep 2012 09:52am
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Thanks for the feedback, think I better just take the time and build a small underground shelter when doing my piers. I thought I could just build a quick small building and drop it in the ground and call it a day. But, sounds like thats not the best idea, so going with a small 6x6' concrete block shelter underground. Started my new plans last night, heading to the farm today.
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MtnDon
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# Posted: 8 Sep 2012 10:00am
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F-5 Shelters They do above and below ground. Doors open in, so debris is not too much of a factor. I have a fear of drowning so I like above ground. Just me. They have a 5 MB online catalog download. Lots of pictures.
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Nick32
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# Posted: 8 Sep 2012 10:55am
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Thanks MtnDon. I am going to look into that. On farmland of the midwest, storms can get ugly.
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