I'm planning a storage shed underneath a deck. I'll assume that the deck is anchored below the frost line and won't move when the ground freezes.

I'd like to build the shed on just a floating gravel pad, which I assume will rise a bit when the ground freezes.

Is it possible to estimate how much overhead clearance is necessary to account for the heave displacement, such that my shed doesn't end up bursting through the floor of the deck?

Luckily I'm in a pretty temperate area and the soil frost depth in my area is only 12 inches, so I expect I won't have too much displacement to worry about (thinking about something like 6" of overhead clearance at highest point), but just wanted to see if anyone had a knowledgeable answer.

  • 1
    I think you would've noticed by now if the ground in your backyard rose 6" every time it froze.... – Drew May 24 '17 at 19:26
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    Yeah, not much of a concern. Frost doesn't usually move stuff that rests on the surface very much anyway. Frost "jacking" is a bigger problem. – isherwood May 24 '17 at 21:27

Think outside the box.

If you are trying to minimize the distance to the deck to have max headroom, then attach the shed roof to the deck, so that water coming through the deck runs off.

Now build your shed but stop the walls a foot from the suspended roof.

From the roof hang 18" walls that have 1" clearance from the sides of the shed. Stuff with insulation. Now if the shed moves up and down, the walls frm the floor telescope with the walls from the ceiling.

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