In our part of Wisconsin the frost drives down several feet into the ground every winter, and it is the single most important number a foundation has to respect. Most of the foundation and flatwork failures I help assess around Grand Chute trace back to one of two things: something built above the frost line that had no business being there, or water that was allowed to collect where it could freeze. Freeze-thaw is not exotic. It is just water changing volume, over and over, in places it should never have been.
The mechanism in one paragraph
Water expands about nine percent when it freezes. That does not sound like much until you multiply it by the volume of saturated soil under a slab, or the water sitting in a masonry joint, and by the number of freeze-thaw cycles in a Fox Valley winter. Each cycle pushes, then releases. Soil under a footing that is above the frost line heaves the footing up; water in a crack widens the crack; water absorbed into the surface of concrete or brick spalls the face off. The force is enormous and patient, and it always finds the weakest, wettest spot.
Why footing depth is the whole game
The reason foundations here are required to bear below the frost line is simple: below that depth the ground does not freeze, so it does not heave. A foundation founded deep enough sits on stable ground all winter. Anything shallow, a porch, steps, a deck footing, an addition someone added cheaply, sits in the zone that freezes and gets lifted every year. That is why the additions and porches fail while the original deep foundation is fine. The required depths are set locally for exactly this climate, and the current numbers are worth confirming against the building code your jurisdiction adopts, which follows the International Code Council model codes on frost-protected footing depth.
When I see a heaved set of steps or a tilting porch, the first question is always how deep the footing goes. Nine times out of ten, the answer is “not deep enough.”
Water is the other half
Frost needs water to do damage. Dry soil below freezing barely moves; saturated soil below freezing is a jack. So the second half of every freeze-thaw failure is drainage. A downspout dumping beside a porch, a grade that sends snowmelt toward the foundation, a window well with no drain, all of them load the soil with water going into winter. Fixing the drainage often matters as much as the footing depth, because you can starve the freeze of the water it needs to lift anything.
On the masonry side, the same water that heaves footings also gets absorbed into concrete steps and block, and then spalls the surface as it freezes, made worse by de-icing salt. Sealing good concrete and keeping salt off it slows that surface damage considerably.
Repair that respects the frost
The durable repair is always the same idea: get the foundation element below the frost line, and get the water away from it. A heaved porch or steps gets rebuilt on footings dug to the required depth, backfilled with free-draining gravel instead of water-holding clay. A spalling surface gets addressed once the movement is stopped, not before, because resurfacing something that keeps heaving just cracks the new surface too. Costs mirror the work: rebuilding steps or a porch on proper footings runs $3,000 to $8,000, more with masonry facing; a full foundation issue is a much larger number. The same depth-and-drainage logic drives whether heaved steps get repaired or rebuilt.
When the fix means rebuilding steps or a porch below the frost line, Appleton masonry who works the Fox Valley will know the local footing depths that keep it from heaving again.
Frequently asked questions
How deep does a footing need to be here? Below the local frost line, which in this climate is several feet. The exact required depth is set by your jurisdiction’s adopted building code, so confirm the current number locally rather than guessing, because building above it is the root of most heave.
Why do my steps heave but my house foundation doesn’t? The house foundation was almost certainly built below the frost line, so it sits on ground that does not freeze. Steps and porches are often poured shallow, in the zone that freezes and heaves every winter.
Does sealing concrete stop freeze-thaw damage? Sealing reduces how much water the surface absorbs, which slows surface spalling, and it is worth doing on good concrete. It does not stop heave from saturated soil under a shallow footing, which is a depth-and-drainage problem, not a surface one.