Shed foundation in cold area

Old 05-22-08, 04:57 PM
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Shed foundation in cold area


I'm planning on building an 8' x 10' shed in an area where the frost line is 4 feet.

My plan was to dig 15" deep, and fill with gravel and compact it. Then pour a 6", 6000psi concrete slab on top of it.

I know frost heave is a problem for bigger buildings, but I'm wondering if it is necessary for such a small shed. The shed won't be holding any heavy loads. (garden tools only).

What is the worst case scenario? I don't care if the shed moves up or down a tiny bit during the freeze/thaw cycle.

Would it cause the concrete slab to be destroyed?..or just small cracks, or nothing at all?

Thanks for any insights.

Doing this manually, so not in a position to dig 4 feet down, and want a permanent foundation.
Old 05-22-08, 05:34 PM
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Shed foundation in cold area

Getting footings below the frost line is a way to eliminate frost heaving.

If you have a floating slab, you can have heaving up that may go away during the warm season (not guaranteed). For an independent structure like a shed the up and down is not a problem, unless it is not uniform and can change slope and drainage. - highways heave every year and come back down good enough since they are not connected to anything stationary.

You do not need an excessively thick slab for a small structure. You just want it to maintain structural integrity. Your 6" thick slab could be be excessive for such a small building, but practical if you are ordering ready-mix with a minimum surcharge. Certainly, the 6000 psi is way to much. If you are concerned with freeze/thaw duability, you could order air entrained concrete to sleep better.

Last edited by Concretemasonry; 05-22-08 at 06:07 PM. Reason: spelling, grammer

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