Concrete Lifting in Winter: Why Green Bay Lifts Wait for the Thaw

You noticed it in September and meant to call. Now it's December, the low slab at the garage door is a sheet of ice every morning, and the snowblower catches the lip on the front walk every time.

Can somebody fix it before spring?

Outdoors, the honest answer is no. Here's why, what the lifting season actually looks like in Green Bay, and what you can get done while the ground is frozen.

Why We Don't Lift on Frozen Ground

These problems come from the ground, not the lifting material. Any method that raises concrete from underneath runs into them.

Frozen soil holds onto the slab

When wet soil freezes, it freezes to whatever it touches, including the underside and edges of your slab. Ice packed into the joints locks the slab to its neighbors.

A slab held like that doesn't rise as one piece. The foam pushes up in the middle, the frozen edges hold on, and concrete doesn't bend much before it cracks.

A slab on frost is sitting at its winter height

Wet soil swells as it freezes and pushes up whatever sits on it. Brown County sits on red, clay-rich glacial soils, and clays and silts are the most frost-susceptible soils there are. By January, a lot of slabs are riding higher than they will in summer, and they don't all ride the same amount.

A simplified example. Two squares on a front walk, side by side:

• ✓Square A sank 1" last summer, next to a downspout that washed soil out from under it.
• ✓Square B sits in the soggy ground by that same downspout. By February, frost has pushed it up 1/2".
• ✓The lip between them now measures 1-1/2".

Lift A to match B in February and it looks perfect. Then the frost leaves. B drops back its half inch, and A, sitting on foam, stays put. Now A is 1/2" too high, a brand-new trip edge facing the other way. Foam can only raise concrete, never lower it.

That's why lifts get matched to where slabs will sit in summer, not where the frost has them in winter. Frost heave vs. settling covers telling the two apart, and precise concrete lifting covers how lifts go wrong when the reference point is off.

The soil underneath is about to change

Frozen soil is part ice. In spring, Wisconsin ground thaws from the top down, and meltwater gets trapped above the layers that are still frozen. Wisconsin's DOT notes that frost can still reach 4 to 6 feet below pavement after the top layer has thawed. That soggy stretch is why the state posts spring weight limits on roads, which average from about early March into early May.

A lift done in January rests on soil that's about to turn soft and wet. Lifting after the ground has thawed and drained means the foam supports the slab on the ground it will actually sit on.

Cold foam is slow foam, but that part is solvable

Lifting foam starts as two liquids that react and expand under the slab. The data sheets we checked want those liquids warmed before use. One says to precondition them overnight to 70–80°F. Another calls for warming both to 60–80°F in extreme cold and lists heated lines among the required equipment. Cold slows the reaction and thickens the liquids.

We warm the chemicals to their data-sheet temperature before injecting, in any season. That's a solvable problem. Frozen ground isn't, and that's the real reason outdoor lifting waits.

Green Bay's Lifting Season, in Real Numbers

The spring start. The frost has to be out of the soil under the slab, and the ground has to drain. Green Bay's normal April low is about 35°F, and frost hangs on deep into spring. In an early year, lifting can start in late April. In a late one, it's May.

The fall finish. Green Bay's normal low drops to about 40°F in October, 29°F in November, and 18°F in December. Statewide, Wisconsin's frozen-road period, declared once frost reaches at least 18" under pavement, starts around December 22 on average. Outdoor lifting usually runs through November and stops when the ground freezes. A hard cold snap can close the window early, and a mild year can stretch it.

Month by month for Green Bay

Normals are 1991–2020, from the Wisconsin State Climatology Office. Caulking needs dry, frost-free joints at 40°F or warmer. Sealers follow their label, commonly 40°F and up with no rain for 12–24 hours. Many coating systems want the slab around 50°F or warmer for a couple of days and several degrees above the dew point. Photo quotes: every month.

Late Fall Is the Deadline That Matters

If you're reading this in October or November, here's why it pays to act now instead of waiting for spring.

• ✓Every thaw feeds the void. A sunken slab with open joints catches snowmelt all winter. Green Bay's March runs above freezing by day and below at night, so that water goes under, freezes, thaws, and carries soil with it. The void under your slab in April can be bigger than it was in October.
• ✓A slab tipped toward the house sends melt to the foundation, right into the loose backfill that surrounds most basements.
• ✓Low spots turn into ice. A sunken apron or stoop holds a puddle that freezes every night. Then comes the salt, and the brine soaks into the lowest slab.
• ✓Snow hides trip edges. Shovels, snowblowers, and plow blades find them anyway, and a blade catching a raised lip can snap a corner off.

One honest catch: caulking weather runs out before lifting weather does. Joint sealant needs dry, frost-free joints at 40°F or warmer, and a 35°F November morning doesn't qualify. If that happens, the lift still does its main job: the slab sheds water instead of collecting it. The joints get sealed on the first good day in spring.

If It Has to Wait Until Spring

• ✓Extend the downspout now. A cheap flexible extension aimed at the lawn takes the biggest source of water away from the slab. Here's how to extend downspouts.
• ✓Keep snow piles off the slab and away from its edges.
• ✓Sand the low spot instead of salting it twice a day.
• ✓Mark the trip edge with a stake or reflective tape so the snowblower and the plow driver know it's there.
• ✓Don't patch the gap with mortar, and don't caulk the slab where it sits. You'd be sealing it in the wrong position, and a rigid patch tends to pop loose after a winter anyway.
• ✓Take photos now with a tape measure at the worst edge, then retake them from the same spot after the thaw. Side by side, they show what's settling and what was just frost.

For the rest of the winter routine (ice melt, shoveling, snow piles), see winter concrete care.

What You Can Get Done in Winter

Get a photo quote. We quote from photos all year. Brush the snow off the slab and its edges first, then send:

• ✓A wide shot showing the slab, the house, and the slabs around it.
• ✓A close-up of the worst edge with a tape measure standing in it.
• ✓Where the nearest downspout or sump line empties.
• ✓A note on whether it looked the same before the snow.

If winter is hiding something, we may ask for one more photo after the thaw before we lock in the plan.

Book the spring work. Once you have a quote, we can put you on the schedule for when the frost is out. Our lifting process walks through what happens on lifting day.

Plan the whole job in the right order. Cleaning, caulking, and sealing all wait for spring too, because none of them work on cold, wet, frost-filled concrete. If you want all of it done, the order is: clean, let it dry, lift, patch the holes, caulk, then seal once the caulk has cured. Around here that usually means lifting and caulking in May or June and sealing after that. See clean and seal concrete and our spring checklist.

Heated Garages and Shop Floors: Ask Us

An interior slab in a building that stays heated all winter is a different situation. The soil under a heated floor may not freeze, and the concrete isn't riding on frost.

That doesn't make it an automatic yes. We'd want to know:

• ✓Is it heated all winter, and how warm? An unheated or barely heated garage behaves more like an outdoor slab, especially near the door.
• ✓Is there in-floor radiant heat? We need to know where the tubing runs before anyone drills.
• ✓How do we get in? The equipment stays outside, so hoses have to come in through a door in January.
• ✓Does the outside apron need lifting too? That part waits for spring, so the inside and outside should be planned together.

Send photos and tell us how the building is heated, and we'll tell you whether it's a winter job or a spring job. Same goes for a garage floor coating: in a heated garage it may be doable in winter, and in an unheated one it waits for a warm slab.

Quick Self-Check: What to Do With What You're Seeing