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caducus
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# Posted: 25 Mar 2018 09:00pm
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I was originally going to build my cabin on 10 concrete sonotubes holding up two girders. However after doing the math on cabin weight and clay I would need to do some pretty wide footings to make that work.
Some people here were suggesting a full foundation pour. A rim of concrete around the base. I wanted to talk about how that would work.
It's a somewhat remote site. I can get my truck in there, but no cement truck, so I don't want to pour too much concrete. I want my frame 18" off the ground.
I have no clue about what my options are, if anyone can offer some input.
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ICC
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# Posted: 25 Mar 2018 09:28pm
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What is the frost depth?
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caducus
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# Posted: 25 Mar 2018 09:47pm - Edited by: caducus
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no frost. temperate climate. no snow either.
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ICC
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# Posted: 25 Mar 2018 11:47pm
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I think a full perimeter concrete footings is probably best, but I would suggest asking locally about how foundations fare with the clay. Clay can be a bugger if it is very expansive. You would only need to go 12" deep; that can be done with the assistance of a rototiller to break the ground. Then a square nose shovel. You can mix concrete with a small portable mixer along with sand & gravel mix and portland cement. Or look into a PT permanent wood foundation. It uses a special 'foundation grade' PT, not the usual lumber yard stuff. But can be done with no concrete at all. Some gravel in the footing trenches, tamped with a jumping jack tamper. Rent one, no need to buy.
Same opinion as before, just modified for checking on what the local officials have to say about the clay.
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caducus
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# Posted: 26 Mar 2018 12:56am
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I guess I'm a bit confused on what the full perimeter footing looks like.
So it's a 14x20 rim? How wide? Is it going the full 18" up to the bottom of my joists?
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ICC
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# Posted: 26 Mar 2018 10:26am
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12" wide, or wider if that is better for low quality soils.
It starts with a footing, 8 " thick with rebar about midpoint. A short poured concrete wall can be formed and placed on top of the footing. That can all be set up with the form boards in place and poured at once or poured in 2 steps.
Or a concrete block wall can be constructed once the footing is in place.
Yes, it is placed , made with the outer dimensions matching the outline of the house.
There is a 'mud sill' 2x that is secured to the top of the concrete work and the floor assembly built on that.
It makes a crawl space which can be either ventilated or not, called a conditioned space.
Some places with clay do have special requirements for doing this, maybe a wider footing so it can 'float' and spread the load better. That is why I suggested checking locally. Clay can be an expense to build on andkeep the building intact.
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snobdds
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# Posted: 26 Mar 2018 12:00pm
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You would be crazy to build an entire poured foundation in a remote location. Mixing 8 yards of concrete is not feasible in a portable mixer to get it all done in one day. You would have cold joints everywhere that would be weak points. Then what advantage would you have? A traditional poured foundation should only be done if a truck can get in. Otherwise there are lots of solutions to your problem.
Pylons are just fine. You don't have the cold thaw cycles to move them around. Clay soil is not ideal, but people have been building on it for centuries. Use those sonotubes with the big base at the bottom to lock it into the ground.
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ICC
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# Posted: 26 Mar 2018 03:09pm - Edited by: ICC
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Not talking about an entire foundation--- just a footing. A little more than 1-3/4 cu yards. Start early, work late. Have helpers, maybe 2 mixers. There are aids like the rebar is there to offer mechanical connection. You form a keyway that connects. You use a compound like Anti-Hydro with portland cement mixed to promote the bonding. Then make a concrete block stem wall on top.
I would do anything I could to avoid piers in clay. Wet clay moves like plasticene and so can the piers. Typical piers are only connected to something solid at one end, the top. I have seen a project dismantled and abandoned after one year because of piers in clay. They started in summer, got thru the winter and in spring when snow melted the ground was sosked and several piers began to tilt. That may have been a bad case but it was costly.
Again, ask locally what has worked without needing a lot of remedial work over the ensuing years.
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caducus
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# Posted: 28 Mar 2018 12:15pm - Edited by: caducus
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Ben trying to find some local knowledge, but it's been hard to come by.
I'll say this, you mention the risks of wet clay. This is on a ridgetop with plenty of great drainage, so at least I have that going for me.
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