Footings in wet soil

(Minnesota)

I have a quick question. I live in Minnesota and my backyard borders some swampy backwaters and is thus pretty moist once you start digging. I would like to build a low (1 foot high) floating deck. I am unsure of how, or if, I can pour footings.

Any advice would be great. I have read about using the precast footings surrounded by regular cement. Does anyone think that would work? I have attached a picture of what I am talking about. Thanks in advance.

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Jun 27, 2011
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Find out your soil type and bearing capacity
by: Editor - Rich Bergman

The very first thing I would want to know in order to answer your question is the bearning capacity and soil type of your soil. This determines virtually everything.

If the soil is wet but its made predominantly of granular sand and gravel mix it still has good load compression. But if it is all fine silty clay which may also have some bio mass as well, you have some big worries.

Some clay, Leda clay in particular is weaker, and can be problematic to build on so you have to have very wide footings.

Precast footings are great and if you have a crane to drop them in place and trucks to deliver them their cost of about $150 is pretty reasonable. But it matters not if the soil can only support 1000 psf and you are loading twice that much.

Until you find out what that soil type will bear, you are throwing darts with a blindfold on.

I would also recommend you spend some time on my deck footings calculator to get a good understanding of how things change with each variable.

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