Repair methods

Mudjacking and slabjacking

If a section of driveway has dropped and now catches your car door, this is almost certainly the right fix and it is far cheaper than you are probably fearing. If your house has settled, it is almost certainly the wrong one. The distinction is worth getting straight before anyone quotes you.

How it works

  1. Drill. Holes are made through the sunken slab in a pattern — around an inch or more across for mudjacking, considerably smaller for foam.
  2. Pump. Material is injected beneath the slab, first filling the void that opened as the soil dropped away.
  3. Lift. Once the void is full, continued pumping pressurizes against the underside and raises the concrete. The crew watches the surface and works across the holes to control it.
  4. Patch. The holes are filled. They remain visible on close inspection, more so with mudjacking's larger holes.

Slurry or foam?

Mudjacking (slurry) Polyurethane foam
Hole size Around an inch or larger Much smaller, roughly pencil width
Weight added Heavy — it is cement and soil A small fraction of slurry
Cure time Hours to a day before loading Minutes
Water resistance Can wash out over time Does not wash out
Void filling Fills what it is pumped into Expands into smaller gaps
General cost $5 – $15 per sq ft $8 – $25 per sq ft

General industry ranges for orientation only — not quotes, and not binding on any contractor. Foundation Repair IQ does not set or quote prices.

The weight argument is the one that should carry most sway. The soil under that slab already failed to support it; adding a heavy cement slurry on top of that soil is not obviously the right response. Foam's lightness is not marketing — it is the main technical reason to pay the premium, alongside not washing out where water was the original culprit.

What it is genuinely good for

  • Driveways and garage aprons that have dropped at a joint
  • Sidewalks and walkways with a trip hazard at a slab edge
  • Patios and pool decks that have settled or now drain the wrong way
  • Garage floors where a section has sunk
  • Steps and stoops that have pulled away from the house

In all of these the concrete itself is sound and the problem is what is — or is no longer — underneath it. That is exactly the problem slab lifting solves, usually in a few hours and for a fraction of what replacement would cost.

Where it is the wrong tool

The limitation that matters

Slab lifting fills a void. It does not create structural support and it does not reach soil capable of carrying a house. If a foundation has settled because the ground beneath it cannot hold the load, filling the gap does not change that — the slab will move again. For a settled house foundation the answer is underpinning, which transfers load onto competent bearing. Anyone proposing to mudjack a settled house foundation as the primary repair is worth a second opinion.

Also poor candidates: concrete that is badly broken up rather than simply sunk, where replacement is more sensible; slabs sitting over an active erosion or drainage problem that has not been addressed; and anything where the void keeps reopening, which is the ground telling you the cause is still running.

Questions worth asking

  • What do you think caused the void, and is that cause being addressed?
  • Slurry or foam, and why that one here?
  • How long before I can drive or walk on it?
  • How visible will the patched holes be?
  • Is there any warranty, and what would void it?
  • If this is near the house — are you confident this is flatwork and not the foundation?

Questions about mudjacking and slabjacking

What is mudjacking?

Drilling holes through a sunken concrete slab and pumping a cement-based slurry underneath it. The material fills the void that has opened under the slab and, as pumping continues, the pressure raises the concrete back toward its original level. The holes are then patched. Slabjacking and concrete leveling are the same process under different names, and the technique is well over half a century old.

What is the difference between mudjacking and polyurethane foam?

The material, and nearly everything that follows from it. Mudjacking uses a heavy cement slurry pumped through larger holes — typically an inch or more — and it is comparatively cheap. Polyurethane foam is injected through much smaller holes, expands in place, weighs a fraction as much, cures in minutes rather than hours, and does not wash out. Foam costs more per square foot. The weight difference is the substantive argument: adding heavy slurry to soil that already failed to carry the slab is not obviously a good idea.

Can mudjacking fix my house foundation?

Generally no, and this is the most important limitation to understand. Slab lifting fills a void and raises concrete; it does not provide new structural support, and it does not reach soil capable of carrying a house. If the ground under a foundation has lost capacity, filling the gap does not stop it happening again. For a settled house foundation the appropriate answer is underpinning, which reaches competent bearing. Mudjacking addresses the symptom; piering addresses the cause. They are not alternatives.

What does slabjacking cost?

It is priced by area rather than by support point, which makes it a fundamentally different economic proposition from piering. General industry ranges put mudjacking in the region of $5 to $15 per square foot and polyurethane foam roughly $8 to $25, with the spread driven by how much lift is needed, how much material the void takes, and access. For a sunken driveway section or patio, that typically lands far below what structural work would cost — which is precisely why it suits those jobs.

How long does mudjacking last?

It depends entirely on whether the reason the slab sank has been addressed. The lift itself is durable — the material stays where it was pumped. But if water is still washing soil out from under a driveway, or the ground is still consolidating, the slab will sink again and the fill will go down with it. Ask what the contractor believes caused the void. If the answer is a drainage problem and the drainage is not part of the plan, expect to repeat the exercise.

Can I walk or drive on it afterwards?

Foam cures in minutes and areas are typically usable within hours, including driveways. Mudjacking slurry needs longer to gain strength — commonly a day or more before vehicle loads. If turnaround matters, that difference is often worth more than the price gap between the two materials.

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Flatwork or foundation?

Getting that right decides whether this is a few hundred dollars or a structural job. A free inspection settles it — licensed contractor in your ZIP code, no obligation.

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