I live in mid wisconsin and am planning on a 40x80' shed and would like
to know what i should be doing for the foundation. I am thinking of
putting a 40x40 concrete slab and would like to ensure that frost heave
does not dammage it.

one contractor said to put 2 inches of styrofoam insulation, but he did
not even see the site, so I'd like to know what to prepare before we
get to the styrofoam. the area has a bunch of trees that will be
removed, stumps pulled and etc. I'm wondering if the existing soild can
be used or if i have to get some gravel