What actually happens during the job
Mudjacking lifts a sunken slab by pumping a slurry underneath it. A contractor drills a pattern of holes, usually an inch or two across, through the low section of concrete. A pump forces a mix, most often some combination of cement, soil, and sand, down through those holes and under the slab. As the material fills the void and builds pressure, the slab rises.
Once the section reaches the level the crew is aiming for, the holes get patched and the job is often finished in an afternoon, which is a big part of the appeal next to tearing a slab out.
Mudjacking versus foam jacking
Mudjacking is not the only way to lift a slab. Polyurethane foam jacking uses smaller holes and a lightweight expanding foam instead of a heavy slurry, and it sets up in minutes rather than needing time to cure. Foam weighs a fraction of what a mud slurry weighs, so it puts less new load on ground that already struggled to hold the slab up once.
Mudjacking usually costs less up front. Foam jacking tends to hold up longer over soft or wet ground, since the extra weight is not there to make the same settling problem worse a second time. Neither one is a universal answer, and which fits a given slab depends on the ground under it more than on either product.
What lifting a slab does not fix
Either method raises the concrete that is already there. Neither one changes why the subgrade under it gave way, whether that is a void washed out by water off a downspout, fill that never got proper compaction, or clay that swells and shrinks with the seasons. If that cause is still active, a lifted slab can settle again, sometimes in a different spot than the first time.
A resurfacer is a different repair entirely and gets confused with slab lifting sometimes. It changes the top of a slab that is already sitting level. It does nothing for one that has dropped. Our page on tear out and replacement covers what it looks like when the base itself, not just the slab sitting on it, is the actual problem.
Pouring instead of lifting
We pour and replace concrete. We do not drill, pump slurry, or inject foam under an existing slab, so mudjacking and foam jacking are not services we offer. What we do instead, when a slab has settled enough that lifting will not hold, is take it out, fix the ground underneath, and pour a new one on a base built to carry it.
If a section of your driveway or patio has dropped and you are trying to decide between lifting it and starting over, that comparison, and what a replacement runs, is worth a call rather than a guess.