Concrete Leveling and Mudjacking: When a Sunken Slab Can Be Lifted

Mudjacking vs Polyurethane Foam Lifting

Concrete leveling, slab jacking, concrete raising and "cement lifting" all name the same idea: drill holes through a settled slab, pump material into the space under it, and let the pressure push the slab back up. The American Concrete Institute's field guide defines slabjacking as raising slabs or filling the voids under them by injecting a material under pressure. The two materials homeowners get offered are a cement grout (mudjacking) and an expanding polyurethane foam.

Mudjacking pumps a wet grout. Missouri's DOT mixes it from topsoil or loam with portland cement and water, or from fine sand, agricultural lime or mineral filler where loam isn't available; ACI notes fly ash is often added so it pumps. Foam lifting (also sold as polyjacking) injects a two-part polyurethane that's mixed at the gun, foams under the slab and expands to do the lifting.

Neither one is the honest answer for every slab. Foam's small holes and light weight suit soft ground and slabs you look at every day; the grout costs less per foot and fills big voids completely. Both raise the slab; neither changes the soil that let it sink. ACI says it plainly: slabjacking will level the slab, but it won't correct poor soil conditions underneath. Foam installers often advertise long service lives. Ask what's actually in writing, and see the questions further down.

How Concrete Lifting Works: Raising a Slab From Below

On a well-run job the crew works in a pattern, and ACI's guide keeps the lift to no more than 1/4 inch at any one hole at a time, moving hole to hole and coming back until the whole panel reaches the string line or laser. Rushing it is how a lifted slab cracks. When it's done, the holes get filled with a repair mortar, and they stay visible; ACI notes slabjacking may not suit a surface where appearance matters for exactly that reason.

One thing worth knowing before the drill comes out: ACI warns the grout follows the path of least resistance and can end up in sewers, drains or other underground lines instead of under the slab. Anyone lifting your slab should ask where your sewer lateral, buried downspout pipes and sump discharge line run. If they don't ask, tell them.

Can This Slab Be Lifted? A Slab Jacking Checklist

Lifting works on a slab that is still one solid piece, has dropped rather than risen, and has stopped dropping. Go out with a straightedge or a level and check yours against these.

Missouri's DOT puts the first one bluntly: badly cracked or broken slabs can't be raised effectively. A surface that's scaled or crumbling will still be scaled after it's lifted; that's a surface problem, covered on our concrete repair page. And a slab that's still settling will keep settling. ACI says that if the soil settlement hasn't stopped, the lifted slab will continue to settle and may need lifting again, and that a slab that keeps sinking was very likely poured on poorly compacted fill. Fix the water first: a downspout emptying at the edge of a walk washes the base out from under it, and no lift outlasts that.

A settling foundation wall is a different problem altogether. That's a structural specialty, not flatwork, and not something a slab lift addresses.

Frost Heave or Settlement? Timing Concrete Leveling in Central Wisconsin

This is where Wausau differs from the cost guides written for warmer places. Wausau averages about 64 inches of snow and roughly 163 nights a year at or below freezing (NOAA 1991 to 2020 normals). Wet, silty soil under a slab grows ice in it and lifts. That's frost heave, and it can make a perfectly good panel look like its neighbor sank.

Frost-Heaved Slabs: Wait for the Thaw Before Lifting

A homeowner in a Fine Homebuilding Q&A described patios that rose more than 2 inches during a stretch of near-zero days, then sank below their original level once the ground thawed. That up-and-down is the tell. If a panel catches the storm door or the snowblower in January and lies flat in June, it's heaving, not settled. Lifting the low panels to meet a heaved one in winter leaves them sitting high when the heaved one drops back in spring.

The lifting itself isn't strictly seasonal; ACI lists "can be done in virtually any weather" among its benefits. The reasons to wait here are about reading the slab and the materials. Measure the drop in winter, measure again in late spring after the frost is out, and decide on the spring number. Missouri's DOT schedules its leveling for cool, not cold, spring and fall weather when the joints are open; ACI warns that lifting in hot weather, when the slab has expanded, can bind it, crack it or throw it out of line. A foam manufacturer's data sheet notes cold slows the reaction and asks for the material to be warmed to 70 to 80°F before use.

Settled Backfill: Why Slabs Need Lifting by the House

The slabs that drop for good, rather than heave and settle back, are mostly next to the house. The soil pushed back against a new foundation is loose fill, and it keeps settling for years, so the patio, the stoop, the walk along the house and the panel at the garage door go down with it. That's also the one place a slab tipping the wrong way does real harm: it sends roof water toward the basement.

The ground under a slab matters too. In the Wisconsin River valley around Rothschild and Mosinee, much of the soil is sand: it drains well, but it settles if it was never compacted, often first at the edges and at the garage door. On the uplands around Wausau and toward Marathon City, silt over glacial till holds water, which is the kind of ground that heaves in a freeze. A sandy-lot slab that dropped once is a classic lift; an upland slab that moves every winter usually isn't.

Driveway Leveling and Other Common Concrete Lifts

Driveway Leveling for a Sunken Panel

The usual driveway leveling job is one or two panels: the one at the garage door where the fill settled, or one at the walk where a downspout ran. If the panel is whole and the drop is under a few inches, lifting it puts the joint back flush for less than a replacement. If half the drive is cracked into pieces or scaled, lifting one panel just makes a level spot on a failing driveway; that's when driveway replacement is the honest conversation. The floor on the other side of the overhead door has its own page: garage floor repair.

Lifting a Patio That Slopes Toward the House

A patio that has dropped along the foundation is the most common lifting job that also fixes a water problem. The goal isn't just level; a patio should pitch away from the house, and a quarter inch per foot is the usual rule of thumb. When you get a lift quoted, ask for the finished pitch, not just "level." If the patio is cracked through or the backfill is still settling on a newer house, a new concrete patio on a compacted base can be the better money.

Mudjacking a Settled Stoop or Entry Slab

A front stoop that has tipped or pulled away from the house is a frequent mudjacking request. Lifting can fix a stoop that settled. It can't fix one that heaves every winter, because the problem is what it's sitting on: Wisconsin's building code wants stoops attached to a house on footings below frost. Same goes for a walk with a raised lip at a joint: lifting the low panel removes the trip hazard if it's low because it sank. If it's crumbling at the edges, see step and stoop repair.

Mudjacking Cost and Concrete Lifting Cost: What Drives the Price

We don't lift slabs, so we have no lifting prices of our own to give you. These are national averages from HomeGuide's mudjacking cost guide (updated November 2025), not quotes and not our prices. Central Wisconsin bids can land anywhere around them.

For a second read, Fixr's concrete leveling cost guide (updated January 2025) puts mudjacking a 100 sq ft patio at $500 to $1,700 nationally. What moves a real bid:

• Material. Foam costs more per foot than grout, often a lot more.
• The void you can't see. The hollow under a slab can run past the low spot, and a bigger void takes more material.
• How far it dropped. An inch takes far less than four, and a deep drop needs more holes and more care to lift without cracking.
• Minimum charges. The rig, the crew and the setup cost the same for one stoop as for five panels, so grouping every low slab into one visit is cheaper per slab.
• Access. A backyard patio behind a fence takes longer than a driveway at the street.
• The add-ons. Joint and crack sealing afterward, and fixing the downspout or grade that caused it, may or may not be in the number.

Lift It or Replace It? When Concrete Leveling Is the Cheaper Fix

Lifting is usually the cheaper fix when it fits. ACI's guide says slabjacking often costs less than half of a new slab, and HomeGuide puts it at 30 to 50 percent less than tear-out and replacement. Replacing panels is the work we do, and we'll still tell you that.

After Mudjacking or Foam Lifting: Joints, Cracks and Water

A lift changes the joints around the slab. ACI notes that even a properly done lift can widen or narrow existing cracks at the surface. Plan on these afterward, whoever does them:

1. Reseal the joints. The joint between the lifted panel and its neighbor, and the gap against the house, need backer rod and a flexible sealant so water stops getting under the slab again.
2. Seal the cracks. Clean, stable cracks get a flexible sealant too. How to pick one is on our concrete crack repair page.
3. Move the water. Extend the downspout past the slab and check that the soil beside it slopes away. Water washing the base out is the most common reason a lifted slab drops again.
4. Watch it one winter. Measure the joint in spring. If it stayed flush through a Wausau winter, the lift worked.

Finding a Concrete Lifting Company Near Wausau

We won't rank or name lifting companies here. What we can do is tell you what separates a good bid from a fast one, the same way we'd want our own work compared. Ask every company these:

• Mudjacking or foam, and which product? For foam, ask for the manufacturer's data sheet.
• What made it sink, and does your price deal with that? A company that can't explain the cause is guessing at the fix.
• How many holes, what size, and how are they patched? Ask to see patched holes on an older job.
• How will you measure the lift, and to what pitch? String lines or a laser, lifted in small steps.
• What happens if it settles again? Get any warranty in writing: what it covers, for how long, and whether a re-lift is included.
• Do you ask where buried lines run? Sewer laterals, drain pipes and sump lines are where grout goes missing.
• Are you insured? Ask for the certificate.

A good written bid lists each slab with its measured drop, the material, the number and size of holes, how they're patched, whether joint and crack sealing is included, what's being done about the drainage, and the warranty terms. If two bids are far apart, it's usually because one leaves out the sealing or the cause.