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Small Cabin Forum / Cabin Construction / Foundation for riverfront cabin in floodplain
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danwheeler
Member
# Posted: 16 Mar 2012 08:48pm
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Hi all, I just signed up - I've browsed through this site over the years while researching but I'm starting to get serious about building something on my property.

I have a little slice on the Wenatchee river in Washington state that I'd like to build on. All of the neighbors say "build high!" so that is what I intend on doing.

My absolute dream is something like the Delta Shelter by Olson Krundig architects:

http://www.olsonkundigarchitects.com/Projects/38/Delta-Shelter

Now that cabin is way over my budget but I still like the idea of it. I can't quite tell from the pictures how they did their foundation.

Does anyone here have experience dealing with cabins on stilts or high foundations? I'm open to all options or ideas.

thanks,
Dan

trollbridge
Member
# Posted: 16 Mar 2012 08:56pm
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Hey danwheeler...welcome!!!!

One members cabin came immediately to mind that may help you. It is member nathanprincipe. His sits pretty high up off the ground. Good luck researching and when you get started post pictures for us all to see

Martian
Member
# Posted: 17 Mar 2012 08:51am - Edited by: Martian
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Dan, I built this one about 13 years ago. It is almost 9' above grade on 6X6's, and has been through 90mph winds, but no floods. There is little threat from current at my location, but if there were, I'd have run diagonal 6X6's upstream bracing.



Building up in the air presents all sorts of challenges when doing it shorthanded and on a low budget, but it can be done.



I found this pic of after the worst storm.



Tom

trollbridge
Member
# Posted: 17 Mar 2012 10:26am - Edited by: trollbridge
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Duh Martian...I forgot all about your other place! Sorry...yours is the highest one on here I think.

danwheeler
Member
# Posted: 19 Mar 2012 01:34pm
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thanks for the pics and information, guys.

Martian's cabin definitely gives me some ideas. Do the 6x6s just sit on top of the cement on a steel anchor embeeded into concrete?

Martian
Member
# Posted: 19 Mar 2012 02:01pm
Reply 


Nope. They are set 36" deep with a rock under each one. I compacted the soil at the bottom of the hole before putting in a flat stone. Then I tamped the soil back in around the pilings. After the banding was put in place, the 4X4 angle bracing went on. During the storm that blew down the tree, I was asleep. It doesn't move, except when a heavy train goes by about 400 yards away. I can feel the vibration a bit.

Tom

danwheeler
Member
# Posted: 19 Mar 2012 02:18pm
Reply 


gotcha, thanks.

The neighbors tell me that when the water comes up it swirls around the soil and causes all kinds of problems.

I've been trying to find information about using steel pipe or I-beams as piers for a foundation but I can't find anything. I dont know if I should drive piles directly into the ground or dig down 3-4 feet and pour concrete directly around a 8" pipe or... ?? I dont want rust to be a problem.

it looks like they used sonotube here but I dont know if the ibeam goes down into the cement or sits on top of it somehow

Delta Shelter

Martian
Member
# Posted: 19 Mar 2012 03:48pm - Edited by: Martian
Reply 


Current wasn't a consideration for mine; just rising water. In a current situation, I'd get down as deep as possible; maybe 8' or so depending on how high you expect the water to get and how strong the current is. I would consider building up the grade around and under the house after setting the piers to create an island of sorts if there is strong current and the likelyhood of trees washing down onto the foundation. That or build the foundation more like a bridge support; long and narrow to take the pressures.

I'm not a big fan of steel in concrete because of the corrosion, but with good heavy pipe or beam, it should last a lifetime, anyway. Would you frame in metal or change over to wood for the actual structure?

If you do concrete piers, bell the hole at the bottom and put in lots of rebar all the way up to the top of the tube. To anchor the cabin down, attach j-bolts to the rebar and bolt the framing down. I might even build some kind of barrier upstream to catch the logs and brush before it gets to the cabin.

Are there any other structures close that you can get ideas from?

Tom

danwheeler
Member
# Posted: 19 Mar 2012 04:04pm
Reply 


well fortunately for me, I do have a big barrier upstream - it's my next door neighbor's mansion/cabin

I'm also on the inside bend of the river on a heavily treed flat so I think the chances of something big and floaty slamming into my place are very low. It's not technically IN a floodway, but it is close. It is definitely considered flood plain.

Most of the other older cabins are standard foundation or some of the new ones are built on high foundation walls with garage space below.

I'd love to do the whole place in steel but I think it will get too expensive. I may just do the piers and a square frame connecting the piers in steel then switch to stick frame on top of that.

thanks for the help and suggestions so far!

Martian
Member
# Posted: 19 Mar 2012 04:40pm - Edited by: Martian
Reply 


You might be surprised at the cost, if you're a welder, that is. But if you have to pay a welder, it probably would be pretty expensive.

Your location sounds secure unless the river decides to straighten out the bend; that would suck! If your neighbor has a mansion/cabin, you might take your tape measure over and look at how they did it. They probably spent a lot of money on engineeering; learn from it.

Tom

danwheeler
Member
# Posted: 19 Mar 2012 04:44pm
Reply 


I do weld. Mostly automotive though.

Do you mean I might be surprised that it is relatively inexpensive? or the other way around?

I only have a little 110 right now but I have access to bigger welders and could definitely justify buying a bigger unit. And I have power on-site too. Not sure how big my service is but I'd guess its 200a.

(looking up steel prices now)

Martian
Member
# Posted: 19 Mar 2012 05:09pm
Reply 


Cheaper. Check out used drill stem. I bought a 12" 60' long I-beam for several hundred dollars from a metal salvage yard years ago. You buy it by the pound a few cents above salvage cost.

Tom

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