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Leif E Greens
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# Posted: 10 Mar 2017 07:51pm
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Hey, I am planning on building a 22x32 cabin with a 6' porch to make it 22x38. 12' high walls with a full gable roof at 6/12. I am just conflicted on what to do for the foundation since the soil is mostly clay. The cabin will be built in an unorganized township so there are no permits or codes. Any advice or feedback is appreciated.
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Graciesdad
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# Posted: 10 Mar 2017 09:32pm
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Just finished building 24 x 32 cabin this Summer, also have clay soil. Had a good gravel/loam mix hauled in and compacted over undisturbed clay soil. I ended up pouring a 6" slab, 12" on edges, following our codes for Northern Minnesota. Also put down 2" pink foam under slab. Built a 2ft knee wall on top of slab for foundation using green treated 2x6 material, it was fast and easy and gives you a crawl space for whatever mechanicals you run. Covered knee wall with metal roofing material which local Big Box center cut in 2ft height. It was economical and looks great
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Graciesdad
Member
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# Posted: 10 Mar 2017 09:55pm
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Tried uploading pictures to get a better idea what I was talking about but not sure what I'm doing wrong. Will try again
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Leif E Greens
Member
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# Posted: 11 Mar 2017 02:35pm
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Thanks for the reply. That is basically what my contractor said I should do. But this means getting a cement truck to the site and a higher cost of the building. I was wondering if a sonatube pier foundation would work on a building this size. I think the frostline here is around 5 feet though.
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bldginsp
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# Posted: 11 Mar 2017 05:31pm - Edited by: bldginsp
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I think a pier foundation for a building that size is risky at best. Certainly would not pass engineering muster. If you drilled down below the frost line for the sonotubes it would work on the short term, but eventually the piers will begin to move independently of each other and the house starts to tweak unless you get under there and 'make adjustments'.
An alternative is a pier and grade beam foundation, where you connect the piers with concrete beams that sit on grade. Usually you put cardboard or styrofoam under them to prevent ground heave pushing against.
But probably a slab with deepened footings is easiest. 5 foot piers would probably use close to as much concrete as a slab, or certainly way more than you want to do by hand, unless you like getting concrete dust in your eyes.
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Leif E Greens
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# Posted: 14 Mar 2017 12:54am - Edited by: Leif E Greens
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Thanks for the reply. I really like the idea of having the pier and grade beam foundation. I don't really want to pour a full slab of concrete on the clay soil. I am just trying to find a foundation that doesn't cost too much and functions well.
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Steve_S
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# Posted: 14 Mar 2017 07:19am
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The foundation is the single most important part of your build, everything else depends on it... yep, just had to be said. A Slab Foundation with Radiant in it is the big win and you would be surprised at the prices... get some estimates and have them break down the costs... The foundation / Base is the absolutely last place you want to come back to and say "I wish I had a done XXX, I should've, would've, could've".
1) removal of organic layer (min 6")
2) supply & compact gravel base
3) supply & install 2" XPS Foam insulation underneath
4) 6mil poly barrier over foam, taped & sealed.
5) 10 / 12mm double perimeter rebar
6) 4x4 reinforcing mesh for concrete
*) 7/8" PEX & Manifold for Radiant Heating
Fibre Reinforced Concrete or light Fly-ash concrete works well, colouring can be expensive but there are different ways to do that which can save big bucks.
A point on costs & usage... 22x32 is an odd form factor which will increase your wastage rate quite a bit. You should likely consider 24x32 (think divisible by 4 or 8)
I got my Radiant Kit & Takagi heater from here (note you can't get a Takagi cheaper from anywhere!) and am very pleased with their products... The manifold assembly almost qualifies as artwork. http://www.radiantcompany.com/ *Lot's of good info & video's there.
Reasonably good guide to Slab on Grade:
http://www.ecohome.net/guide/slab-grade-construction-step-step-guide
Older CMHC Doc which is a good overview & summary
http://publications.gc.ca/collections/collection_2011/schl-cmhc/NH15-457-1998-eng.pdf
I submitted my design to bldg dept (attached below) which is different that it used 4" XPS vs the required minimum of 2" XPS.
NOTE That there are many companies out there doing concrete a bit differently. There are more & more companies that mix on site and only mix what you need for the pour, so no waste and no shortages and quite a bit cheaper while offering a bit more flexibility... for example, if you want to colour the concrete, conventionally, the whole "batch" in the mixer has to be done an that can get very expensive very quickly BUT with the smaller mixing, you can mix colour in the topping layer, so only one small batch of colouring is needed.
Hope it helps
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Kamn
Member
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# Posted: 14 Mar 2017 07:39am
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Just a thought, but before anyone suggests a foundation type, ask where its being built.
If you are speaking about northern Ontario, then a slab on grade would not be a good idea at that size. It will eventually have some heave
For the amount of work involved in a pier and beam, may just consider digging out and doing a block wall/footings just below frost line.........this may cost a little more but think of what you get, storage, cellar for preserved foods, no worries about lifting...etc
Just a thought
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Steve_S
Member
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# Posted: 14 Mar 2017 09:10am
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For your information... The Frost Protected Slab Foundation is also commonly referred to as "Alaskan Slab Foundation" and is used in Alaska, Yukon, North West Territories & Nunavut as well as all the Northern Reaches of Canadian Provinces & Territories where concrete is available.
On lands with Permafrost, the most common alternative is to also use Steel Pile Foundations driven deep in the permafrost preferably to bedrock which can be very expensive and difficult due to the short building periods. The cost of bringing in concrete into remote areas is extremely high therefore not used very much.
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Leif E Greens
Member
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# Posted: 16 Mar 2017 09:59pm
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Thank you everyone for your advice. I will be sure to run these ideas by my contractor.
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bldginsp
Member
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# Posted: 16 Mar 2017 10:09pm
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Agree with Kamn. You can do a block wall yourself, step by step over time, entirely with a small mixer. Lot of work but done correctly it will be there for the grandkids.
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rockies
Member
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# Posted: 17 Mar 2017 10:15pm
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I'm looking at a Multipoint Space Frame foundation. They cost about $14-18 per square foot (Canadian) but offer a lot of advantages over a concrete poured foundation or piers.
http://multipoint-foundations.com/
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