Polyurethane Concrete Lifting vs. Mudjacking
Two methods dominate residential concrete slab lifting: polyurethane foam injection and mudjacking (also called mud-jacking or slabjacking). Both work by pumping material underneath a settled slab to fill voids and raise it back toward level. The real difference comes down to what gets pumped – a dense cement-based slurry versus a lightweight expanding polymer – and that single difference drives nearly every other tradeoff between the two: hole size, cure time, control during the lift, and cost. Ghost Concrete Leveling uses polyurethane injection on the residential and light commercial slabs we lift across The Woodlands, Conroe, and Spring, Texas, and this page lays out how the two methods actually compare, plainly, so a property owner can judge which fits their situation.
Neither method is right for every slab, and neither one is a permanent fix for whatever caused the ground to move in the first place. This comparison covers the material, the process, the practical differences in hole size and cure time, where each method tends to make sense, and the limitations that apply no matter which one gets used. If you're weighing a quote or trying to understand what a contractor is proposing, this is the technical detail behind it.
Side-by-Side Comparison
The table below lines up the two methods factor by factor. Both are legitimate ways to lift settled concrete; the right one depends on the slab, the sub-grade, and the priorities for the project.
| Factor | Polyurethane | Mudjacking |
|---|---|---|
| Material used | Two-part expanding polyurethane resin | Slurry of cement, soil, sand, and water |
| Material weight per unit of lift | Roughly 2–4 lbs per cubic foot expanded | Roughly 100+ lbs per cubic foot |
| Injection hole size | About 5/8 inch – dime to nickel sized | Typically 1 to 1.5 inches or larger |
| Expansion behavior | Expands and reacts within seconds, filling voids as it grows | Does not expand; slurry fills voids at the volume pumped in |
| Control during lifting | Small, incremental injections allow the lift to be monitored and stopped precisely | Lift tracks the volume pumped, so fine adjustment relies heavily on crew experience |
| Void-filling characteristics | Injection pressure can migrate into smaller voids and cracks | Fills larger voids well; may not reach finer voids as readily |
| Cure time | Typically hardens in 15–30 minutes | Can take one to several days to reach full strength |
| Return-to-use time | Often usable within about an hour | Commonly 24–48 hours or more before full vehicle loading |
| Moisture interaction | Closed-cell foam is largely inert to water once cured | Cement-based mix can be affected by saturated or continuously wet sub-grade during placement |
How Polyurethane Lifting Works
Polyurethane lifting starts with a pattern of holes drilled through the slab, each about the diameter of a dime or nickel – small enough that most get patched flush and are hard to spot once the surrounding concrete weathers a little. A two-component polyurethane resin is pumped through those holes under pressure. The two components react on contact and the mixture begins expanding within seconds, pushing into the void beneath the slab and compacting the loose soil around it as it grows.
Because the foam expands rather than relying on volume alone to create lift, a technician can work in small increments, checking slab elevation between injection points and adjusting before moving to the next hole. The material is also a fraction of the weight of a cement-based slurry, which matters on thinner slabs or where the soil underneath is already loose – less added weight means less risk of that section settling again simply from the material's own mass. Cure happens fast: the foam is typically hard enough to bear weight within 15 to 30 minutes, and most driveways or walkways are back in service within about an hour.
How Mudjacking Works
Mudjacking – also called slabjacking – is the older of the two methods and has been used to lift settled concrete for decades. It works by drilling larger holes, generally 1 to 1.5 inches across, through the slab in a grid pattern. A slurry mixed from cement, soil, sand, and water is then pumped through those holes under pressure, filling the void beneath the slab and, as more material is added, gradually raising it.
The mud slurry doesn't expand the way polyurethane foam does – the lift comes directly from the volume of material pumped underneath the slab. That means larger voids need more material, and more material means more weight sitting on the sub-grade. Mudjacking mix generally needs one to several days to cure to full strength, so contractors will often ask that the area stay off vehicle traffic longer than they would with a polyurethane job. Done correctly by an experienced crew, it remains a proven, cost-effective way to lift many slabs, and it has been a standard method in the industry for a long time.
Material Weight and Injection-Hole Comparison
Weight and hole size sound like small details, but they're often the two factors that decide which method actually fits a given slab.
Where Lighter Material and Smaller Holes Matter
On thinner slabs, slabs over previously disturbed fill, or sections near sensitive landscaping and irrigation lines, adding a large volume of heavy slurry underneath can work against the goal – the added weight can contribute to settling again if the sub-grade is already marginal. Polyurethane's lighter weight per unit of lift reduces that added load, and its smaller injection holes mean less patching and less surface disruption, which is part of why it tends to fit pool decks, thin sidewalk sections, and slabs close to structures.
Where Mudjacking's Heavier Mix Is a Reasonable Choice
Mudjacking's heavier slurry isn't a drawback in every situation. On thick slabs, large driveway or warehouse floor sections, or projects where the sub-grade is stable and well compacted, that extra mass isn't a liability, and the material cost per cubic foot pumped is typically lower than polyurethane. For large-volume voids where a lot of fill is needed, mudjacking can be the more cost-effective option, and it remains a widely used, legitimate method for exactly those cases.
Precision, Control, and Cure Time
The biggest practical difference on the job site is how precisely the lift can be controlled. Because polyurethane expands after injection and reacts within seconds, a technician can inject a small amount, watch the slab respond, and stop or adjust before overcorrecting. That kind of incremental control is harder to achieve with mudjacking, where the lift is a direct function of how much slurry has been pumped in – experienced crews manage this well, but the material itself doesn't give the same real-time feedback that an expanding foam does.
Cure time is the other major difference. Polyurethane reaches load-bearing strength in minutes, which is why polyurethane-lifted driveways and walkways can typically be walked or driven on again within about an hour. Mudjacking slurry cures more like a concrete patch – it needs time to lose moisture and gain strength, often a day or more before the area should carry vehicle weight. Neither timeline is a defect; it's a function of what each material is made of, and it's worth asking any contractor for their expected cure and return-to-use window before work starts.
Suitable Applications for Each Method
Matching the method to the slab, rather than defaulting to one option for every job, is what an honest evaluation should do.
Situations Where Polyurethane Tends to Fit Well
- Thin slabs, pool decks, and sections where added weight is a concern
- Areas needing a fast return to use, like driveways and entryways
- Slabs where precise, incremental lift control matters
- Locations where minimal hole size and patching are a priority
Situations Where Mudjacking Can Be a Sound Choice
- Thick slabs or large-volume voids needing significant fill
- Projects where budget favors a lower material cost per cubic foot
- Stable sub-grade conditions where added slurry weight isn't a concern
- Situations where an extended cure window before use is acceptable
Limitations of Each Method
Lifting a slab with either polyurethane or mudjacking raises the concrete back toward its original position – it does not, by itself, fix why the slab moved in the first place. Settlement is usually caused by something happening in the soil underneath: erosion from a drainage or gutter issue, a slow plumbing leak washing out fine material, seasonal expansion and contraction of expansive clay soils, or poorly compacted fill from the original build. If that underlying condition isn't identified and addressed, a lifted slab can settle again over time, regardless of which material was used to raise it.
Not every slab is a good candidate for lifting with either method – a slab that's badly cracked, broken into multiple pieces, or sitting over a large active void may need replacement instead of injection. And no reputable contractor can guarantee permanent results with either polyurethane or mudjacking, because neither method controls what the soil underneath does after the work is finished. An honest evaluation should tell you whether lifting makes sense for your slab, or whether replacement is the more realistic option.
Why Ghost Concrete Leveling Uses Polyurethane
We use polyurethane injection because of how it fits the kind of residential work we do most across The Woodlands, Conroe, and Spring, with service expanding into Houston, Tomball, and Klein – driveways, walkways, pool decks, and garage floor slabs where fast return to use and minimal surface disruption matter to the homeowner. The smaller injection holes patch cleanly, the incremental control lets us dial in a lift without overcorrecting, and the short cure window means a driveway isn't blocked off for days. That said, mudjacking is a legitimate method with its own place in the industry, and for very large-volume commercial pours or budget-driven projects where those specific tradeoffs make sense, it can be the more practical choice. We focus on polyurethane because it matches the scale and priorities of the jobs we take on, not because the alternative is unsound.
Questions to Ask a Concrete-Lifting Contractor
Whether you call us or someone else, these questions will tell you a lot about how a contractor approaches the work.
- What material will be used to lift the slab, and why is it recommended for this job?
- How large will the injection or drilling holes be, and how will they be patched?
- What is the expected cure time before the area can bear weight?
- How soon can the area return to normal use – foot traffic and vehicles?
- Has the cause of the settlement been identified, or just the symptom?
- What happens if the slab doesn't respond well to lifting – is replacement discussed as an option?
- What warranty or written terms, if any, cover the work?
- How much experience does the crew have with this specific type of slab or application?
Frequently Asked Questions
Is polyurethane foam as strong as mudjacking mud?
Cured polyurethane and cured mudjacking slurry both provide solid support once set, but they get there differently – polyurethane relies on the foam's compressive strength and the compaction it creates in the soil around it, while mudjacking relies on the cured cement mixture acting like a hardened base layer. Both are proven approaches when installed correctly for the situation they're suited to.
Why are polyurethane injection holes smaller?
Because polyurethane expands after it's injected, a small entry point is enough to introduce the material – the foam does the work of filling the void as it grows, rather than needing a wide hole to pump a large volume of slurry through. Mudjacking's larger holes are needed to move enough of the heavier mix to achieve the same lift.
How soon can the area be used after each method?
Polyurethane typically cures to a load-bearing state within 15 to 30 minutes, so many driveways and walkways are back in use within about an hour. Mudjacking slurry needs longer to gain strength, often a day or more before the area should carry vehicle traffic, depending on conditions.
Does either method fix the reason the slab settled?
No. Both methods lift the existing slab back toward level, but neither one addresses the underlying soil condition – erosion, drainage issues, plumbing leaks, or expansive clay movement – that caused the settling in the first place. That's a separate diagnosis, and sometimes a separate repair.
Which method does Ghost Concrete Leveling use, and why?
We use polyurethane injection because of its smaller holes, faster cure time, and the incremental control it gives us during the lift, which fits the residential driveways, walkways, and pool decks we work on most. Mudjacking remains a legitimate method that can make sense for other project types.
Get an Honest Read on Your Slab
If you're comparing methods or quotes, we can walk you through what we see on your specific slab and explain why polyurethane may or may not be the right fit. You can read through our polyurethane concrete-leveling process, or check our concrete-leveling cost guide for a sense of typical pricing factors before you call. Commercial property owners dealing with uneven sidewalks or parking areas can see how this applies to their situation on our commercial trip hazard repair page.