Mudjacking vs. polyjacking vs. structural piers

Mudjacking and polyjacking lift a sunken concrete slab by filling the space beneath it. Mudjacking uses a cement-based grout and polyjacking uses expanding polyurethane foam. Both are suited to slabs such as walks, driveways, patios, garage floors and some interior floors. Neither stops the soil from continuing to settle or erode. Structural piers are a different repair: they carry a footing or slab on deeper support. If the house’s footing is moving, slab lifting isn’t a substitute.

Three different questions

	Mudjacking (slab jacking with grout)	Polyjacking (polyurethane foam)	Structural piers
What it does	Pumps a cement-based grout under the slab to fill voids and raise it	Injects expanding foam under the slab to raise it and fill smaller voids	Transfers the load of a footing or slab to deeper soil or rock
Typical use	Exterior flatwork; filling larger voids	Exterior and interior slabs; smaller holes and lighter material	House footings and, with slab brackets, interior slabs
Holes	Larger (about 2⅝ in., per MoDOT)	Smaller (about 9/16–¾ in., per MoDOT)	Excavation at each pier location, or through the slab for slab brackets
Fixes the cause?	No	No	No. Supports the structure, but drainage and moisture still matter

How the two lifting methods differ

The Missouri Department of Transportation’s maintenance guidance is a clear public description of both methods:

Grout: soil or loam mixed with Portland cement, or a sand, lime and mineral-filler mix. Drill holes are generally about 2⅝ inches.
Raising: lift gradually, “not more than 1/4 in. at each hole at a time.”
Polyurethane: a water-blown, closed-cell, high-density hydrophobic foam injected through holes of roughly 9/16 to ¾ inch.

MoDOT treats foam as the more expensive option and uses it to lift slabs or fill small voids rather than large ones. For bridge approach slabs it describes combining the two: grout to fill voids and stabilize at lower cost, foam to lift. It also warns that badly cracked or broken slabs can’t be raised effectively.

These are highway-agency practices, not rules for your driveway. They are still a useful, non-commercial account of the trade-offs.

What monitoring found

Highway agencies have tracked lifted slabs over time:

Oregon DOT (FHWA-funded, 2002): slabs lifted with polyurethane settled up to about 0.4 inch over two years. The foam itself didn’t lose compressive strength after burial.
Oregon DOT follow-up (2003): most monitored points kept settling slowly. The report recommended identifying why a slab settled before choosing a fix, and noted that polyurethane “does not guarantee success.”
Oregon DOT interim report (2000): foam filled test holes of about ¼ inch and larger but not the finest gaps. Conventional pressure grout filled voids only near the injection hole.
Kentucky Transportation Center (2019): two years after polyurethane lifting, “the panels have settled again.” One slab settled back almost to where it started.

Those were highway slabs under traffic, not house floors. The shared lesson still applies: lifting treats the void, not the reason the void formed. If water is washing out the base or the soil is still consolidating, a lifted slab can sink again.

When piers are the relevant comparison

Slab lifting and piers get compared because both “raise” concrete, but they answer different questions. Ask yourself, or better, ask an engineer:

Is it a slab or the house? A sunken patio or sidewalk is a slab problem. Cracks in brick, sticking doors and a sloping floor are among the signs of foundation movement listed in ASCE’s homeowner guide. If the footing is moving, slab lifting doesn’t address it.
Is the movement finished? If settlement has stopped and the cause is fixed, filling a void may be enough. If it is ongoing, a deeper support may be considered.
What’s under it? Uncompacted fill, erosion from a downspout, and shrink-swell clay behave differently. See the Soils & structures section on your metro page.

Piers are covered in detail in Foundation repair methods, including what their product evaluations do and don’t cover.

What local companies say they offer

Among 115 company websites reviewed for this edition (October 27, 2026), mudjacking was named on 7, polyjacking on 10 and polyurethane foam injection on 15. Some of those firms also install piers. These are website statements, not verified jobs. Use the method filter on any list to see which companies name a method, then confirm in writing.

Questions for a slab-lifting proposal

Why did this slab settle, and what will stop it from happening again (downspouts, grading, joint sealing)?
Which material, how many holes, and what size?
What lift is targeted, and what happens if the slab cracks during lifting?
Are voids being filled as well as the slab lifted?
Is this a slab problem or a structural one, and how did you decide?
What’s the warranty on height, and what does it exclude?

Sources checked 2026-10-28