# 16x16 cabin foundation options



## meismike09 (Dec 6, 2013)

Hello, I'm new to site and in the planning stage of 16x16 cabin in Eastern Upper Peninsula of Michigan. Was planning on Sonotube piers (12), but after considering that I'm building on land that is limestone only a couple of feet down, I'm wondering if I could get away with another foundation type. Any thoughts/ideas? Thank in advance.


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## homstdr74 (Jul 4, 2011)

Why? Why do anything different than building with your piers on *bedrock*?


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## Darren (May 10, 2002)

Whatever you do it has to resist the freezing temperatures that penetrate the limestone. You have to prevent frost heave.


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## meismike09 (Dec 6, 2013)

I'm not sure why. That's why I've presented the question. I'm not quite sure I will be able to penetrate the rock when digging in, and my assumption was that the limestone isn't going to allow the normal heaving and sucking that would occur if it wasn't there. Doesn't the rock serve as an uncompromising "footing", already, and if so, why try to dig past it? Could I get away with another "above ground" foundation method that would naturally be supported by the rock that is, in some cases, only a foot below the earth?


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## homstdr74 (Jul 4, 2011)

meismike09 said:


> I'm not sure why. That's why I've presented the question. I'm not quite sure I will be able to penetrate the rock when digging in, and my assumption was that the limestone isn't going to allow the normal heaving and sucking that would occur if it wasn't there. Doesn't the rock serve as an uncompromising "footing", already, and if so, why try to dig past it? Could I get away with another "above ground" foundation method that would naturally be supported by the rock that is, in some cases, only a foot below the earth?


I am not an engineer, but it seems to me that unless you have something like an artesian well in that stone it shouldn't heave. That said, I don't live in such brutal temperatures (altho' this year we are getting close).

Seems to me that if you really felt threatened by the bedrock heaving you could drill down a couple of feet and drive long enough rebar into the hole so's it would run up into your pier.


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## John_Canada (Aug 17, 2013)

Check out something called Frost Protected Shallow Foundation. Can use it to also heat the house using infloor. We are about the same latitude and I will likely be using this for a 2500 sqft house. I would have thought the piering would have been a good idea tho.


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## Darren (May 10, 2002)

The bed rock won't heave. Anything not attached will heave by freeze thaw. If it was several feet to bedrock you might get enough friction to over come the freeze thaw forces. I've seen piling for docks in New Jersey that ice jacked out of the ground while others didn't budge. The difference was the ones that popped had been jetted in. The ones that stayed put were put in with a pile driver. The difference was the amount of skin friction on the piling.

Your foundation has to resist freezing. If not, over time parts can be jacked out of the ground and not on an even basis.


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## dirtman (Sep 15, 2011)

You may never get any frost in your foundation. I've lived in the Northwest lower for most of my life and because the snows usually come early we seldom get more that a few inches of frozen ground. Down a couple of feet I would have no concerns.


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## meismike09 (Dec 6, 2013)

Appreciate the input, I've got a few months to concoct the plan, we'll see where it goes.


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## Clod Kicker (May 7, 2012)

I've heard of greasing the poles and wrapping them with plastic to prevent them from following the surrounding earth when it expands due to frost. I imagine it would work with wood as well as concrete poles (Sonotube).


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## Gray Wolf (Jan 25, 2013)

Starting with stating that I know nothing..... 

The bedrock isn't going to frost heave. If you are worried about the soil "grabbing" your sonotubes and lifting, use the smallest ones you can. The amount of bottom contact surface of even a small tube should be enough. Sonotubes, pier blocks and the like are intended to have a large enough bottom surface so that they don't sink into soil and buried deep enough to be stable, side to side.

I think that your greater problem with a tube-type support in shallow soil is that there won't be enough buried to resist tipping to the side.

I'd dig down to the rock and pour a larger diameter footing, say 2'.

For a 16' x 16' cabin, 9 of them should be enough since your max span will only be 8'.

Good luck on your project!


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## wy_white_wolf (Oct 14, 2004)

meismike09 said:


> I'm not sure why. That's why I've presented the question. I'm not quite sure I will be able to penetrate the rock when digging in, and my assumption was that the limestone isn't going to allow the normal heaving and sucking that would occur if it wasn't there. Doesn't the rock serve as an uncompromising "footing", already, and if so, why try to dig past it? Could I get away with another "above ground" foundation method that would naturally be supported by the rock that is, in some cases, only a foot below the earth?


The problem is that water on top of the limestone will seep inbetween it and the concrete of the sono tube. Lifting it and causing the frost heave. Because of the limestone the heaving will be slower as little dirt/soil to fill in the created gap as it melts.

If you can't get down deep enough to be below the frost line consider building up to the amount needed. If that's 4' and you can only get down 2' consider adding 2' of sand to build up to the needed 4'.

The other potion would be do everting you can to improve drainage around the sturcture to eliminate the water. If the limestone bedrock slopes then you could but a water barrior and drainpipe along the uphill side to keep it from under the peirs.

WWW


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## meismike09 (Dec 6, 2013)

Another good question would be, whether a tractor powered auger could make it through the rock without damage? I'm assuming the answer is no.


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## Gray Wolf (Jan 25, 2013)

It's a little cabin. 

Mixing that much mud will be a pain. Buying that little redimix will be pricy. 

Perhaps look at some options. UBC allows wood foundations so there are materials that could be used other than concrete. There are also a lot of pole-building-type homes/cabins doing just fine with and without building permits.

I would set treated vertical 6"x6" perimeter posts on the rock, build the cabin floor/walls to them and then cut off the tops.


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## homstdr74 (Jul 4, 2011)

Gray Wolf said:


> It's a little cabin.
> 
> Mixing that much mud will be a pain. Buying that little redimix will be pricy.
> 
> ...


Personally I don't like to put wood into the ground anymore. I've been there, done that. Too many little varmints in the dirt willing to destroy the wood, and if it's treated, they're still waiting for the treatment to wear down.

Yes, mixing concrete is a hassle, but well worth it. I have outbuildings in which I've had to replace treated posts before, but the concrete I placed has never given me a problem in the 35 years we've lived on this property.


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## fishhead (Jul 19, 2006)

What about digging out a normal footer right to the limestone and pouring it on top?

Then you could put blocks up a few courses to the elevation you want. Maybe just do it on 2 sides to reduce the amount of blocks and work.


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## tbone0106 (Mar 2, 2013)

Whether you go with posts or piers or a traditional footer and block or concrete, the key is making sure that EVERY POINT is resting on the bedrock. If some piers, for example, are resting on the limestone and others are not, you will get differential settlement and your cabin will be out of level and out of plumb within months.

I once watched a crew building a new house about 1/4 mile down the road from where my partner and I were building another one. Their project was a pretty standard ranch style on a block foundation with a crawl space. As their backhoe was digging out their footer, they hit a "hump" in the bedrock about 2' down, roughly in the middle of the house, right where the front door was going to be. They hit that same hump when they dug across the back side. They thought, "Cool! Bedrock is good! Won't have to worry about the foundation here!" The ends of the house rested on a standard "mud mat" with some re-steel, resting on undisturbed earth. Not long after the house was completed, the ends settled, but the center didn't, and that house literally tore itself apart. The roof actually ruptured and split open from front to back. Those fellows had to tear that house down, all the way to the footer, and start all over again.


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## Clod Kicker (May 7, 2012)

Assuming the limestone is bedrock in your area, the footers can be poured right onto it. In spots where you reach 44" deep* without reaching bedrock, I suggest these:* http://www.bigfootsystems.com/include/best_footings.htm* placed on undisturbed soil. Requirements are they be twice the width of the circular concrete form.

*whatever the code depth is in your area.


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## meismike09 (Dec 6, 2013)

Also found "cribbing" with railroad ties, and really liked the idea and the looks of it way up off the ground with all that heavy stuff holding it up. This method allows for easy adjustments through time. The ground is well drained... The highest point on the property. Anyone ever dealt with that type of foundation building? Found out that the sonotubes (5' with 4 in the ground and 1 above) would require about 3-4 80 lb bags of quikcrete each and it gave me anxiety... That's a lot of haulin and mixing. I have access to water but a half mile away. Not to mention the cost of it. Don't have to go cheap but I don't want to go too heavy on a 4-5 times a year shack either.


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## gobug (Dec 10, 2003)

Check on a rubble trench foundation. That is basically a trench just a bit below frost line filled with rubble (not sand or gravel). Frank Lloyd Wright used it. I considered it for my CO mtn home (no foundation yet).
Gary


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## HuskyBoris (Feb 14, 2013)

this may help
http://www.apexhomeinspections.biz/articles/foundation_failures.pdf


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