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rootwad
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# Posted: 15 Jul 2013 06:38pm
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What kind of foundation would you recommend for a 12x12 stilt cabin in a floodplain? There would need to be 8' of clearance beneath the cabin. I'm not sure if this would make a difference on building materials/techniques, but it will not be in the floodplain long term....it will eventually be moved to higher ground when I find better land (hopefully within five years, but for the sake of the unknown, lets go ahead and say ten years).
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SubArcticGuy
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# Posted: 15 Jul 2013 06:58pm
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Does it just flood or does it flow? That would make a huge difference in how you would do the foundation.
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rootwad
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# Posted: 15 Jul 2013 08:24pm
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I haven't gotten the land yet, but some of my possibilities cover both of those situations that you mentioned....one is in a flow area, the rest are in a no-flow zone. I am basically trying to learn as much as I can about building in a floodplain so I can make a smart decision.
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OwenChristensen
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# Posted: 16 Jul 2013 07:18am
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I'd put it on treated 12' -6x6's dig them in four feet and x brace them. I've never seen them sink, but up here in frost country they can lift. To cure that we notch the corners near the bottom and pour concrete around them, only at the bottom, back fill with gravel.
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Kudzu
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# Posted: 16 Jul 2013 07:43am
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You better check and see if building is allowed on the tract you are talking about. If it is, there will probably be stipulations attached.
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Martian
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# Posted: 16 Jul 2013 08:43am - Edited by: Martian
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This is my cabin in a flood plain. Its 9' above grade; 3' above the highest recorded flood. We haven't had a flood since I built it back in '99; so I haven't tested it under those conditions. But, we have had 90mph winds, and I was asleep in the loft....never even heard them!
However, when I looked out the next morning, this was the yard!
Its built on 12' 6X6's set three feet deep with angular bracing. All the cabin walls have cross bracing, too.
Tom
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OwenChristensen
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# Posted: 17 Jul 2013 01:34am
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Tom, I like your Jeep. I bought a '66 Bronco and am restoring it.
I like your stilts. Good cross bracing make it all work, doesn't it?
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Martian
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# Posted: 17 Jul 2013 08:43am
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Thanks, Owen. I sometimes think about replacing the Jeep, but then, I realize I'd have more money in my vehicle than I do my house! Doesn't make sense to put that much money into something without a bathroom, at my age!
Rigidity is all about triangulation!
Tom
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rootwad
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# Posted: 17 Jul 2013 04:49pm
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Thanks for the feedback!
Owen- I like the notch idea. I think the footing is what I was most curious about. I've spent 10 years dreaming/planning/researching for building on higher ground and had my plan in place. But when the possibility of building in a floodplain came up, all the info I found was geared toward larger structures. I was curious if my small cabin on stilts (taller than it is wide) would require a different sort of foundation/footing.
Tom- Glad that tree branch ended up on the ground instead of your cabin! Thanks for the pictures...that's good motivation for me.
I have another question that I'm having trouble finding an answer to. How would I go about moving something so narrow onto and off of stilts? My plan is to build from scratch using as many recylced materials as possible, and if that's what I end up doing, then I don't have to worry about moving the cabin ONTO the stilts.....but I will have to move it off in a few years. However, if I end up purchasing a ready-made shell for my cabin, I'd have to move the cabin ONTO the stilts as well as move it OFF later. As far as getting a ready-made cabin onto the stilts, the options I've found include jacking the cabin up and building the foundation up to meet it, or placing the cabin on a ready-made foundation, but I don't see how either of those could possibly be viable/safe options for me since my cabin is going to be so small. If I built the foundation up to meet it, I'd have to jack the cabin sky high to allow enough clearance to sink the 12' posts four feet into the ground. If I were to have the posts in place before jacking the cabin, I don't see how it would be possible to move the cabin onto the stilts once I have it jacked up. I've seen in done a couple of feet off the ground, but I only see impending doom at the heighth I would need.
Set me right folks! I obviously have no experience with moving/jacking a building and I'm eager to learn from your experience.
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Martian
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# Posted: 17 Jul 2013 08:02pm
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Unlike Owen, I did not notch my piers. The load is never up; so I put a good footing; ie, large rock, under my piers. I also used packed dirt around the piers...no concrete. The dirt tightens itself around the pier every time it rains. The only movement has been during severely dry weather, and the back door drug some. Now that we have had some rain, it doesn't drag any more. After 14 years, there are no cracks in the sheetrock which would indicate movement. I have built another cabin, and this one is rental property now.
As for getting your small cabin up and down, or just down, I would hire a crane, with spreader bars, if they can get in. It won't take too much of one to hold your structure. If a crane can't get in, you can get a bunch of blocking and start jacking it up. It'll be easier to set your piers after its in the air than it will be to jack it up and move it onto the structure. If you stick build, like I did, make sure you build it to be lifted, or at least supported elsewhere than the piers, at some point. Going down, a chain saw will take care of getting the piers out of the way, once you have the cabin supported. You might be able to pull them over with a large enough vehicle if you want to salvage them, but then again, they may just break!
It may be easier to build it with the idea it will be disassembled at some point. Put on a metal roof, for instance; so you can unscrew it. Use construction grade screws to put it together. Build your walls to be taken apart at the corners by just pulling the trim to get to the screws. In other words, build in sections and use screws. This will make getting it both up and down easier.
Tom
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rootwad
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# Posted: 18 Jul 2013 06:15pm
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Tom, you have given me some excellent advice. If I end up with a pre-built, the crane sounds like a good way to go (assuming it can get in, like you said). But I really like your idea of building in sections that can be disassembled, and I'm thinking that's the direction I'm going to go. I found an awesome website showing a 12x16 cabin that was built off-site with self-contained panels (fully insulated with windows installed), then trucked to the location and assembled. I'm sure most folks on this forum have stumbled across this already, but if not, here's the site: http://tinyhousetalk.com/prefab-tiny-cabin/
The pictures seem fairly informative, but once I get into sketching my plans I'm sure I'll come up with all sorts of questions that I can't figure out.....so I'll be back soon!
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bldginsp
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# Posted: 19 Jul 2013 11:49pm
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I was just thinking that the amount of lumber you would use to make enough blocking to safely hold the cabin in the air at that height is probably two or three times the amount of lumber in the cabin itself. The crane idea is great except that they are very expensive. It takes ten minutes to lift and lower the cabin, but it takes two hours of driving and setup time to get the crane ready. Since weight is not much of an issue a smaller capacity crane is all that's needed and maybe they are less expensive, I don't know.
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Martian
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# Posted: 20 Jul 2013 01:08pm
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It would take a lot of cribbing to get the structure that high. I looked at moving my cabin, and I needed a lot of 6"X6"X4' to support it. Add the cost of moving it, about $6000, and you know why I just build another one.
A crane to lift a small structure like that would cost around $300-400 here. It may be more wherever he is. A couple of friends to help lift the sections in place couldn't possibly drink that much beer!
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rootwad
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# Posted: 20 Jul 2013 06:57pm
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Good lord, Tom and bldginsp, that IS a bit cost preventive for me. I hadn't even gotten to the stage of pricing for any of that. I was trying to put together some good options first so I wouldn't waste the time of hard working people to give me price quotes on something I might not even use. Looks like building the cabin in sections is going to be the way I go. I'll just write "beer" instead of "crane" on my piggybank".
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Martian
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# Posted: 20 Jul 2013 07:13pm
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Quoting: rootwad I'll just write "beer" instead of "crane" on my piggybank".
That's what I'd do, too. Have fun.
Tom
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Martian
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# Posted: 21 Jul 2013 07:19pm - Edited by: Martian
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Rootwad, If you did want to go the prefab route, I would bet we could figure a way to get it onto the structure, and stay with in your budget.
I'm a cheap SOB. I never pay for heavy equipment if I can invest time and energy to accomplish the same task. I was given a steel framed hay truck bed. I used it for a deck for 9 years. Getting that sucker 9 feet in the air, with only my ex-wife to help, was a trick. I eventually decided to put hinges down one side, lean it up against the piers, jack it up, bolt the hinges to the rim joist, and swing it up into position. I jacked on that thing for several hours...small hydraulic jack. I'd get it up 6" on one end, brace it, and go jack up the other end 12". Brace it, and keep going back and forth until I had it level. worked like a charm!
I bet a little prefab wouldn't be heavier than a steel frame with 2X6 decking on it. At least not by much. You could use the same technique and then slide it over once it was level. Just build a framework to lift it, attach it to the foundation, lay the building over, attach the bottom to the lifting frame, Start jacking!
Then, put decking on the lifting frame, and you have a deck, too!
Tom
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rootwad
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# Posted: 21 Sep 2013 01:37pm
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Back in business....my computer crashed earlier this summer but I wasn't in too big of a hurry to get it fixed. Tom, you had me at "cheap SOB". Your idea of lifting a prefab like you did your hay truck bed intrigues me. Wouldn't have ever thought of doing it that way. How would I go about sliding the structure over once it's lifted?
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Martian
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# Posted: 21 Sep 2013 03:50pm
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Come-along or levers come to mind, but being lazy, as well as cheap, I'd hook the Jeep's winch to it and drag it over!
Tom
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