You got two quotes for the same sunken slab. One crew mudjacks, the other uses foam, and the numbers aren't close. Both say their way is better.
Know this up front: foam is the only lifting method we use. We'll still tell you where mudjacking makes sense, because sometimes it does.
For why slabs sink and every repair option, replacement included, see how concrete lifting works. This is just the head-to-head.
What Each Method Pumps Under Your Slab
Every lifting method fills the empty or soft space under a slab, then keeps filling until the slab rises. The difference is what goes in.
- Mudjacking pumps a slurry of soil or sand, cement, and water. Some mixes add lime, fly ash, or clay. It's thick, gritty, and heavy, and the pump pressure is what raises the slab. Once it sets, it's a hard, cement-like fill.
- Stone slurry grout is a cousin of mudjacking: finely ground limestone mixed with water, sometimes with cement added.
- Polyurethane foam, or polyjacking, starts as two liquids that mix at the injection gun. They react and expand into a rigid, closed-cell foam. The expansion is what does the lifting.
The Side-by-Side
| Polyurethane foam | Mudjacking | |
|---|---|---|
| Hole size | 5/8", about a dime | Typically 1–2" |
| Weight of the fill | A few pounds per cubic foot | Around 100 lb per cubic foot, sometimes more |
| What lifts the slab | The foam expanding | Pressure from the pumped slurry |
| Water | Waterproof once cured, won't wash out | Can erode if water keeps getting underneath |
| Back in use | Walk right away, drive the same day | Usually a day to a few days before it should carry a car |
| Upfront cost | Higher | Usually lower |
| Lifespan | Generally rated longer, with no single agreed number | Cost guides commonly say 5–10 years when done well |
| Patches left behind | Small | Larger |
| Interior slabs | Well suited: small holes, little mess | Possible, but messier |
| What the fill is | Petroleum-based plastic | Mineral-based (soil, sand, cement) |
That last row is a fair point in mudjacking's favor. If you'd rather not have plastic in the ground, mudjacking and stone slurry are mineral fills.
Where the Differences Actually Show Up
The holes
A dime-sized patch and a patch the size of a quarter or bigger don't look the same, especially on a front walk or a stamped or colored patio. Every hole gets patched either way, and no patch perfectly matches 20-year-old concrete. Smaller patches are just easier to live with.
The weight you're adding to soil that already failed
This is the difference we think matters most.
Say a 10-by-10-foot driveway slab has dropped, and there's an average of 2" of empty space under it. That's about 17 cubic feet to fill.
- Mudjack slurry at roughly 100 lb per cubic foot: about 1,700 pounds of new weight sitting on the same soil.
- Lifting foam at a few pounds per cubic foot: somewhere around 50 to 100 pounds.
Firm, dry ground may carry that extra weight fine. Loose backfill or soggy clay, usually the reason the slab sank in the first place, may not.
Washout
Spring melt and a wet April send a lot of water under slabs around here. Cured foam is closed-cell, so it doesn't soak up water and doesn't erode. A cement-based slurry is more porous, and if water keeps running under the slab, it can wear away at the fill.
Highway engineers have seen the same thing. A 2017 Missouri Department of Transportation research brief on slab stabilization reported that cement grout had been phased out there because of its erosion potential, with polyurethane now doing the job.
Neither fill stops water from eroding the soil around it, so fix the downspouts whichever method you pick.
Getting your slab back
Foam sets within minutes. You can walk on it right away and drive on it the same day. Mudjacking slurry has to set up first, and national cost guides put that at one to three days before the slab should carry real weight. For a driveway, or the only path to your front door, that counts.
Upfront cost
Mudjacking almost always quotes lower. National cost guides updated in 2026 put mudjacking at roughly $3–$6 per square foot and foam at $5–$25, a much wider spread. The fill is the big reason. Soil, sand, and cement are cheap. Lifting foam isn't.
The gap can grow on a big washout under a big slab, where material becomes a larger share of a foam quote. If the ground is dry and stable and price matters most, that's a legitimate reason to choose mudjacking.
Longevity
Most longevity claims come from someone selling one method. Cost guides commonly give mudjacking 5–10 years when done well and credit foam with lasting longer, without agreeing on a number. Either way, the fill is rarely what gives out first. The soil under it moves, and water is almost always what moves it.
Wisconsin Conditions That Tip the Scale
- Slow-draining clay. Much of the Green Bay area sits on clay and silt laid down in old glacial lakes. It holds water and drains slowly, so the ground under a slab stays wet long after every rain and thaw. A light fill that doesn't mind water counts for more here.
- Loose backfill along the house. Stoops, patios, walks, and AC pads next to the foundation sit on soil that was pushed back in after the basement was dug. It's the softest ground on most lots, and the worst place to stack heavy fill.
- Spring melt. A winter's worth of snow melting at once soaks that backfill. That's why so many sunken slabs show up in April and May.
- Frost. Wet, fine-grained soil heaves when it freezes, and neither method stops that. A slab that only looks off in late winter may be frost-heaved, not sunk, and nobody should lift it until the ground thaws. Our lifting season runs from spring thaw to freeze-up.
- Road salt. Salt flakes the surface but has nothing to do with sinking, and neither method fixes it. A penetrating sealer helps protect concrete that's still sound, which is a separate job we also do.
Which One Fits Your Situation?
| Your situation | Better fit | Why |
|---|---|---|
| Sidewalk square out by the street, firm dry ground, lowest price wins | Mudjacking is reasonable | Weight and washout matter less on stable soil |
| Patio, stoop, or walk right against the foundation | Foam | Light fill on the loosest soil on the lot |
| AC or heat pump pad | Foam | Small holes, light fill, and little mess around the equipment (see our AC pad guide) |
| Garage floor or other interior slab | Foam | Small holes and no gritty slurry inside the building |
| Slab where a downspout or sump line was dumping | Foam, after you move the water | A fill that won't wash out, in the spot water already proved it can reach |
| Driveway you need to park on tonight | Foam | Drive on it the same day |
| Stamped, colored, or exposed-aggregate concrete | Foam | Smaller patches where patches show the most |
| Slab that was mudjacked before and sank again | Usually foam | Adds very little weight on top of what's already down there |
| Large washout under a big slab, firm ground, tight budget | Get quotes for both | Material cost can make mudjacking much cheaper here |
| Slab broken into pieces, crumbling, or pushed up by roots or frost | Neither | No lifting method fixes these. See is concrete lifting worth it |
Where Stone Slurry Fits
Stone slurry grout sits in the middle. Its holes are about 1" across, smaller than mudjacking and bigger than foam, and it's a mineral fill, which suits people who'd rather skip plastic. It's still a heavy, water-based mix, and when the blend is light on cement, water can erode the limestone over time. Set time depends on the mix, so ask before you plan to park on it.
Comparing Two Quotes? Make Them Apples to Apples
Before you compare prices, check:
- Same slabs, same goal. Are both lifting the same squares to the same finished height and slope?
- What's underground. Did they ask about buried downspout lines, sump discharge, and drain pipes? Any fill pumped under a slab will follow an open pipe.
- Joint sealing. Is caulking the joints and cracks included? Sealing keeps water from getting back under the slab, whatever fill is down there.
- The cause. Did they tell you what sank it and what to fix? If not, you'll be doing this again no matter which method you pick.
- What happens if it settles again. Ask whether there's a written warranty and what conditions come with it.
For vetting the contractor itself, see how to choose a concrete contractor.