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Small Cabin Forum / Cabin Construction / riverbank, frost, very sandy soil + rocks, need urgent foundation advice
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kanesta
Member
# Posted: 28 Jun 2014 15:31
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Hey guys,

Sorry I have yet more questions but here is my situation.

I'm building a cabin in Quebec about 4 hours north of Montreal, super cold area (in mountains, -30 C for weeks at a time, intense frost and then the road breaks apart during thawing in spring)

It's in a remote area, and I have a good deal to have a hole dug and foundation installed this year. But I will lose this opportunity if I wait until next year - I will have to have machinery brought in and the cost will go up. It has to be done by September. But I don't want to jump in too fast either and build the wrong foundation.

I feel too ignorant to make this "snap" decision, but here goes:

THE SOIL:
The result of the soil / perc test says it is very, very sandy - over 50% sand and highly permeable.
There are lots of rocks and tree roots.
It's on a river bank, about 50 feet from the river, up a slope. The exact spot where it would be build has only a slight slope (about 3 feet lower on the river side).
The frost depth must be something like 5 feet at least.
The area is very wet and rainy too.

THE PLAN:
I want an 8' basement - I wanted poured concrete but I think it's too remote. Will have to go with cinder blocks I guess. The local culture is to build on stump posts, but I would really like to avoid this. Just a few people have basements (blocks I think).

Any suggestions about what type of footing / structure of the foundation? Am I going to run into trouble with concrete blocks with all the frost heaving and horizontal forces? What other issues or modifications should I be aware of?

When I read through the forums, everybody seems to have very different ideas and different local conditions, so it's just bewildering. I can't screw up the foundation. Any advice you have would be greatly appreciated! THANK YOU

A picture of the site is included.
site
site


Just
Member
# Posted: 28 Jun 2014 18:18 - Edited by: Just
Reply 


At one time there was a P. T. LUMBER basement option in Ontario,, not sure about Quebec . Perhaps you could check that out . google pressure treated basements

OwenChristensen
Member
# Posted: 28 Jun 2014 21:12
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I think I might be the only one here that thinks a unheated basement is a waste of time, but I stand by it. Frost posts with good drainage is the best option, or if under 4 or 500 sq. ft. on skids.

Owen

Don_P
Member
# Posted: 28 Jun 2014 22:39
Reply 


Very permeable is good, if the water can't hang around and saturate the soil there is little potential for frost heave.

There are ways to greatly strengthen a block wall such as going with 12" block, using horizontal and vertical steel just as if in a poured wall and filling cores with grout. I would check with local contractors and see whether a poured foundation is possible first though. Often people think they are too remote and never explore that option.

old243
Member
# Posted: 30 Jun 2014 22:09
Reply 


With proper footings and proper perimeter drains, your sandy soil should be ideal. In a cold snowy area There is sometimes little or no frost, under the snow cover. The exception is where snow is removed , driveways walks etc. The big thing is to possibly have additional drainage on the upslope side to remove water before it gets to your foundation, if possible have your drains come to the surface , downslope,so you don't need a sump pump. Sounds like you still need to do more legwork , before you decide. good luck old 243

leonk
Member
# Posted: 1 Jul 2014 10:20
Reply 


I wouldn't build a basement in a place like that, you're too close to the river. Do you know the water table level in the spring?
If you insist, I'd talk to others in the area and perhaps may be even an engineer. To your point, you don't want to screw the foundation.
Nice place, btw.

kanesta
Member
# Posted: 1 Jul 2014 12:32
Reply 


@leonk, Thanks. I'm not too too worried about the water table - they said the water table was 15 feet down during the soil test in mid-May. The high water mark is around the first week of May. I went there at that moment and the water level was still all the way down the slope - I would say at least 12 or 13 feet vertically down from the site. The river basin is so wide, it doesn't go up vertically more than a foot or two usually (but rivers can be unpredictable). The basement would extend to a couple of feet above ground too so maybe 5.5 or 6 feet underground. What would happen to say a cinder block basement with an impermeable membrane during extreme flooding, if the water table were to reach it? I don't think it would happen but I'm curious how damaging it could be.

PatrickH
Member
# Posted: 1 Jul 2014 17:22
Reply 


Heres an example of how strong block foundations are URL

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