If you are researching how to fix a sunken driveway, sidewalk, patio, or pool deck around Knoxville, you have probably come across two names: mudjacking and polyjacking. Both raise settled concrete back toward its original grade, but the material, process, and long-term performance are very different. This guide explains how each method works, what it costs, how long it lasts, and why Knoxville Concrete Lifting specializes in polyurethane lifting instead of traditional mudjacking.
What Is Mudjacking?
Mudjacking — also called slabjacking, slab raising, or cement grouting — is the older of the two methods. A crew drills 1"–2" holes through the sunken concrete slab, then pumps a slurry of Portland cement, limestone or sand, and water beneath it. As the slurry fills the void, it generates upward pressure and lifts the slab. The holes are patched with mortar, and the slurry is left to cure.
Mudjacking has been used for decades and can work on thick, heavy slabs sitting on relatively stable soil. It is usually the lower-cost option per square foot, which makes it attractive for budget-focused projects. However, the cured slurry weighs roughly 100 pounds per cubic foot — far heavier than the polyurethane foam used in polyjacking.
What Is Polyjacking?
Polyjacking — also called polyurethane concrete lifting or foam jacking — uses a two-part, high-density polyurethane resin. Technicians drill much smaller 5/8" injection ports, then pump the resin beneath the slab. The chemicals react and expand within seconds, filling voids, compacting loose soil, and raising the concrete with precise control.
The expanded foam weighs only about 4 pounds per cubic foot, is hydrophobic, and cures to 90% strength in roughly 15 minutes. That means the slab is ready for foot traffic immediately and full vehicle traffic shortly after the crew finishes.
Side-by-Side Comparison
| Factor | Mudjacking | Polyjacking |
|---|---|---|
| Material | Cement, sand/limestone, water slurry | Closed-cell polyurethane foam |
| Hole size | 1" – 2" | 5/8" |
| Weight added | ~100 lbs per cubic foot | ~4 lbs per cubic foot |
| Cure / use time | 24 – 48 hours before vehicle traffic | 15 minutes before full vehicle loads |
| Water resistance | Can wash out or erode over time | Hydrophobic; will not absorb or wash out |
| Soil compaction | Fills voids but adds load | Fills voids and densifies soil |
| Typical lifespan | 8–10+ years on stable soils | Permanent under normal use |
| Upfront cost | 20–30% lower per sq ft | Higher per sq ft, longer value |
| Best for | Thick slabs on very stable soil | Most residential & commercial slabs in East TN |
Where Mudjacking Struggles
- ×Adds heavy load to already-failing soil
- ×Large, visible injection holes
- ×24–48 hour cure time before driving on it
- ×Slurry can shrink, crack, or wash out
- ×More likely to re-settle on clay or karst soils
Why Polyjacking Wins Here
- Lightweight foam does not stress weak soil
- Dime-sized 5/8" injection ports
- Ready for vehicle traffic in 15 minutes
- Waterproof and chemically inert
- Densifies soil for long-term stability
Why East Tennessee Soil Makes the Difference
Knoxville sits on a challenging mix of expansive red clay and karst-influenced limestone. Clay swells when wet and shrinks when dry, creating voids and settlement. Karst terrain has hidden cavities and variable rock layers. When a slab has already sunk, the soil beneath it has failed in some way — whether by erosion, compression, or washout.
Adding 100 pounds per cubic foot of mud slurry to that failed soil is a gamble. In some cases it works for years; in others, the extra weight accelerates re-settlement. Polyurethane foam adds almost no load, fills every contour of the void, and actively compacts the soil column as it expands. That is why we believe it is the smarter long-term investment for most Knoxville-area properties.
Cost: Short-Term vs Long-Term
Mudjacking often quotes lower per-square-foot prices, which can make it look like the better deal. But if the slab re-settles in 5–8 years, you pay for the original lift plus a second lift — and possibly damage to the concrete from repeated drilling. Polyjacking typically costs more upfront but is backed by our written lifetime materials warranty against re-settlement of the lifted slab.
At Knoxville Concrete Lifting, we have a $1,500 minimum for all lifting jobs. Most residential polyurethane lifts in Knoxville and surrounding East Tennessee fall between $1,500 and $2,400, depending on slab size, lift height, void volume, and access. Every quote is flat-rate and delivered in writing.
Why We Only Offer Polyurethane Lifting
We are not anti-mudjacking — it has its place in the industry. But after lifting concrete across East Tennessee for more than 15 years, we have seen too many mudjacked slabs come back sunken. We chose to specialize in polyurethane lifting because it gives our customers better results, fewer callbacks, and a warranty we can stand behind.
If you are comparing quotes from a mudjacking contractor and a polyjacking contractor, ask each one: What happens if the slab settles again? How much weight are you adding to the soil? How soon can I drive on it? The answers usually tell you which method is the better value.
Still Have Questions?
Choosing between mudjacking and polyjacking depends on your specific slab, soil, and how long you plan to stay in the home. We offer free, no-pressure estimates across Knoxville, Maryville, Sevierville, and every community in between. We'll inspect your concrete, explain your options, and give you a flat-rate written quote.
Get an Honest Comparison for Your Slab
Not sure whether your sunken concrete is a candidate for polyurethane lifting? Call or request a free estimate and we'll tell you straight — no pushy sales, no surprise charges.