If your driveway has a slab that dropped at a joint, a sidewalk square that catches every toe, or a patio that now tilts back toward the house, you do not automatically need to tear it out and start over. In a lot of cases the concrete itself is fine. It just sank, and it can be lifted back to where it belongs. That process is called concrete leveling, and it is usually faster and cheaper than replacement.
Here is how it works, the two methods we use, what can be lifted, and how to tell whether leveling is the right call or whether the slab is truly past saving.
Why Concrete Sinks in Rochester
Concrete rarely sinks because the concrete failed. It sinks because the ground underneath it moved. The usual causes here are a base that was never properly compacted before the original pour, soil that washes out from poor drainage, and our freeze and thaw cycles slowly working voids open under the slab. Water is almost always involved. Once there is an empty pocket under a corner of the slab, the weight of the concrete does the rest and that corner drops.
What Concrete Leveling Actually Is
Leveling fills the empty space under the slab and lifts the concrete back to grade, without removing it. We drill a series of small ports through the slab, pump material underneath until the void is full and the slab rises evenly to the right height, then patch the ports. The slab you already have goes back to level. There is no demolition, no new forming, no waiting weeks for a fresh pour to cure. Most jobs are walkable the same day.
Mudjacking vs Foam Lifting
There are two ways to fill that void, and we use both depending on the job.
Mudjacking pumps a cement based slurry under the slab. It is the proven, cost effective method, well suited to heavier slabs like driveways and garage floors where the extra weight of the fill is not a concern. The access holes are slightly larger.
Foam lifting, sometimes called polyjacking, injects an expanding polyurethane foam instead. The foam is lightweight, so it will not add load to a base that is already soft, it is waterproof, it cures in minutes, and the access holes are smaller. It usually costs more than mudjacking. It shines on sidewalks, walkways, and situations where you want the fastest turnaround and the least visible patching.
We walk the slab and tell you which method fits, rather than defaulting to whichever one we happen to prefer.
What Can Be Leveled
Most flat residential concrete is a candidate: driveways, sidewalks and walkways, patios, garage floors, front steps and stoops, pool decks, and shed pads. The question is never really the surface. It is the condition of the slab, which is what decides whether we lift it or replace it.
Leveling vs Replacement: When Each Makes Sense
Leveling is the right call when the slab is structurally sound and has simply settled. If the concrete is in one or two solid pieces, the surface is in decent shape, and the problem is height rather than crumbling, lifting it is faster, cheaper, and less disruptive than a new pour. Replacement is the right call when the slab is badly cracked into many pieces, the surface is spalling and breaking apart, or the base underneath has failed so completely that lifting it would only buy a short reprieve. When it is a close call, we quote both, explain the tradeoff plainly, and let you decide on real numbers. Some of this overlaps with the repair work on our masonry and concrete repair page, so if you are not sure which bucket your slab falls into, that is a good place to start.
Frequently Asked Questions
How long does concrete leveling last?
When the void is properly filled and the drainage cause is addressed, a leveled slab holds for many years, often as long as the surrounding concrete. Foam in particular is waterproof and does not wash out. The thing that shortens any lift is leaving the water problem that caused the original settling unsolved, so we look at drainage as part of the job.
Is concrete leveling cheaper than replacement?
In most cases, yes, often a good deal cheaper, because you keep the slab you already have and skip demolition, disposal, new forming, and the cost of fresh concrete. It is only the wrong economy when the slab is too far gone to save, in which case lifting it is money spent twice. We tell you honestly which situation you are in.
How long does the job take?
Most residential concrete leveling jobs are done in a few hours to a day. Foam cures within minutes, so foam lifted slabs are typically ready for use the same day. Mudjacked slabs take a little longer to set. Either way it is a fraction of the time a full replacement and cure takes.
Can a sunken slab be dangerous?
A dropped sidewalk square or step creates a trip hazard, and a patio or slab that has tilted back toward the house can send water at the foundation instead of away from it. Leveling fixes both the trip edge and the drainage direction at once, which is one of the reasons it is worth doing rather than living with.
