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Small Cabin Forum / Cabin Construction / Need Help With Post Foundation
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sadlad
Member
# Posted: 7 Jul 2011 06:45pm
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Hi All,
What a great forum! I just recently bought a Cabin in the finger lakes area. The Cabin is 30 years old (16 X 32). It has 4X4 inch treated post for the foundation. The cabin sits on a slop (Front end is about 12 inches off the ground and the back in is about 32 to 34 inches of the ground). I am not sure if the posts were set in concrete. The issue is that there has been lift because of frost and the post are all angled about 85 degrees toward the slope side. The positive is that the floor (construction and joist) is solid and the cabin floor is level. The entire cabin has lifted and moved on the horizontal. What would be the best way to assure that I have another 20 years left before the Cabin falls?! I am not sure if the post went below the 42 - 46 inches to get past the NY frost line. It may be possible that I could get under the house from the sloped side and dig 3 - 5 post holes that would go below the frost line (with sonotube/rebarb and concrete).

- Or do you think I really need to go as far as 48 inches?

Also - would it do me any good to replace all the slanted posts (or add one next to them) even if on the 12 inch side of the cabin I won't be able to dig below the frost line?

Any suggestions would be greatly appreciated.
all my best
sadlad

adakseabee
# Posted: 4 Dec 2011 09:53pm
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Sadlad, I recently became aware of this forum and when I came to your dilemma, I saw that no one has offered any solution. On the face, it appears that you have a difficult problem to solve. You mentioned that the cabin has 4x4 treated post foundation. Exactly how many posts constitute the foundation and where are they located? Are any running down the center of the cabin? Is the 32 foot dimension parallel or perpendicular to the direction of the slope? On the downhill side does the slope get steeper beyond the building? Finally, do the posts show any rot or insect damage? Look closely where the posts enter the ground. What I have in mind are three possible solutions as described below.

1. Assuming the posts have not deteriorated, installing cross-bracing among the posts, provided there is sufficient clearance to work under the building. (Minor excavation by hand may be necessary to provide adequate clearance). Cross-bracing may prevent further overturning movement of the posts, but is not a permanent, long-term solution if you wish to keep the cabin beyond a decade or two.

2. Another solution that is more costly and is the minimum I feel that is required if your posts have rot or insect damage is to install steel I-beams under your cabin supported on both ends of each beam with a properly constructed concrete pier.

3. Or, for a long-term solution, I would recommend raising the cabin using cribbing, steel I-beams, and house jacks, raise the cabin sufficiently high to allow low clearance excavating equipment under the cabin and install properly installed posts or a concrete stem wall around the perimeter, at least on the two sloping side and downhill side.

Regardless, I would obtain the services of a licensed structural engineer to advise you based on the actual circumstances, i.e., site conditions, post and building condition, local government permitting agency, cost, etc.

Good luck!

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