Concrete · Service

Concrete leveling, including who is telling you which method to use

Mudjacking and polyurethane injection both lift sunken slabs. Nearly all the advice comparing them is written by companies that only offer one. Here is what each is actually better at.

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In short

What is concrete leveling?

Concrete leveling raises a sunken slab back to its original height by injecting material through small holes drilled in the slab and filling the void underneath. Two methods dominate: mudjacking, which pumps a cementitious slurry, and polyurethane foam injection — often called polyjacking — which injects an expanding polymer. Both work. Which is better depends on the slab, the soil and the access, and almost nobody offering one of them will tell you when the other wins.

Triggers

Signs you need concrete leveling

A driveway, walkway or patio panel sits visibly lower than the one next to it
There is a lip at a joint or a sidewalk section big enough to trip on
A garage floor or apron has dropped away from the threshold and left a gap
Water now pools on a slab that used to drain, or runs back toward the house
Steps or a stoop have tilted and pulled away from the building
A pool deck or patio slab has settled unevenly around its perimeter
You can hear a hollow sound tapping parts of a slab, suggesting a void underneath

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The job

How concrete leveling actually works

Working out why it sank

Slabs settle because something under them moved — soil consolidating under fill, a poorly compacted trench where a service was run, water washing fines out from beneath, or a downspout discharging next to the slab edge.

Watch for: A quote given without any discussion of the cause. Lifting a slab over an active erosion path buys you a year. The water source has to be found and dealt with, or the same panel drops again.
Assessing whether the slab is worth lifting

The concrete itself has to be sound enough to be raised as a unit. A slab in a few large pieces can be lifted; one broken into many fragments or with a surface that is spalling apart cannot.

Watch for: A leveling quote on a slab that is genuinely at the end of its life. Lifting badly deteriorated concrete produces a level surface that is still failing, and the money would have gone further toward replacement.
Choosing the method honestly

Mudjacking uses larger holes and a heavier slurry, and works well on thick slabs over reasonably stable soil. Foam injection uses much smaller holes, weighs very little, expands to fill voids, and is generally faster to return to service — which is why it dominates on driveways and around structures.

Watch for: A single-method contractor explaining why the other method is unsuitable in general terms. Ask instead what specifically about your slab and your soil favours their method. A vague answer is a sales answer.
Drilling and injecting

Holes are drilled through the slab in a pattern, material is pumped through them, and the void beneath fills. Lifting is done gradually, in stages across the panel, so the slab rises evenly rather than being levered at one corner.

Watch for: Lifting too fast or from too few points. Concrete has very little tensile strength and forcing a panel up at one point is a good way to crack it during the repair.
Monitoring the lift

The technician watches the slab edge against a fixed reference, or uses a laser, and stops at the target height. Neighbouring panels and any adjoining structure are watched at the same time.

Watch for: Nobody measuring against a reference. Over-lifting is a real risk, and a panel raised past its neighbours is a new trip hazard in the other direction.
Patching the holes and finishing

Injection holes are filled with a cementitious patch. They remain visible as small circles, more noticeably with mudjacking's larger holes than with foam's.

Watch for: An expectation that the repair will be invisible. It will not be. Level, safe and stable is the goal; cosmetically seamless is not what this repair delivers.
Joint sealing and drainage correction

Open joints and cracks get sealed so surface water stops running into the base again, and the drainage that caused the settling is corrected — extending a downspout, regrading, or fixing a leak.

Watch for: Joint sealing skipped as a small extra. It is the cheapest part of the job and it is the part that stops water re-entering the void you just paid to fill.

Money

What does concrete leveling cost?

Leveling is normally a fraction of the cost of replacing the same slab, which is the main reason to consider it. It is usually priced by the area lifted and the volume of material needed to fill the void. Foam injection typically prices higher per job than mudjacking. See the Cost Guide.

See the full concrete leveling cost guide — by material, size and region →

Straight answer

When concrete leveling is the wrong call

Everyone else ranking for this is paid when you say yes. Here's when you shouldn't.

The slab is broken into many pieces or the surface is spalling apart. Lifting requires the concrete to move as a unit. Badly deteriorated concrete raised into position is still deteriorated concrete, and you will replace it soon anyway.
The cause of the settlement is still active. A leaking service line, a downspout discharging at the slab edge, or ongoing erosion will empty the void again. Any leveling done before that is fixed is a temporary result sold as a permanent one.
What has actually moved is the house. A slab settling next to a foundation that is itself moving is a symptom. Foundation movement is a different trade with a different assessment, and lifting the flatwork around it hides the evidence.
The slab is only a small area and you dislike the visible patches. On a short front walkway where replacement cost is modest, some homeowners reasonably prefer a new, unmarked slab to a levelled one with rows of patched holes.
The slab was never thick enough or reinforced for its use. A driveway poured too thin will keep cracking under vehicle loads whatever height it sits at. Levelling corrects the elevation, not the specification.
You are about to replace it for other reasons anyway. If the driveway is coming out next year for a widening or a new layout, this is money spent on something you are demolishing.

Your options

Types of concrete leveling

Mudjacking vs foam injection

The full method comparison, written without a product to sell.

Why slabs sink

Sunken concrete, uneven sidewalks and failed patio slabs, diagnosed by symptom.

Freeze-thaw and slab care

What makes concrete deteriorate, and what maintenance actually helps.

Compare concrete options side by side →

Before you sign

What to check when hiring for concrete leveling

Why do you think this slab sank, and what stops it happening again?

The single question that separates a repair from a deferral. You want soil, water or compaction in the answer.
Do you offer both mudjacking and foam, or only one?

Not disqualifying — but it tells you how to weigh their recommendation. A single-method contractor recommends their method.
What specifically about my slab and soil favours the method you are proposing?

Forces a concrete answer instead of a general argument about the industry.
How many holes, what size, and where will they be?

They stay visible. On a decorative or highly visible slab, hole size and pattern are worth discussing before, not after.
How will you measure the lift, and what stops over-lifting?

A fixed reference or a laser. Lifting by eye against a neighbouring panel is how new trip hazards get created.
Is joint and crack sealing included?

It is what keeps water out of the void you just filled. Cheap to add, expensive to omit.
What warranty is there, and does it cover further settlement?

Read what is excluded. Warranties that exclude "soil movement" on a repair caused by soil movement are worth understanding clearly.

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Local pros

Concrete Leveling near you

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Related work

Often done at the same time

Concrete Repair

When the surface, not the height, is the problem

Concrete Installation

When lifting is no longer worth it

Driveway Installation

Replacing rather than lifting a driveway

Concrete Demolition

Removal when the slab is finished

All concrete services →

FAQ

Concrete Leveling — questions people ask

Still have a question? Talk to our team →

Which is better, mudjacking or polyurethane foam?

Neither is better in general, which is why almost all the confident advice on this comes from companies selling one of them. Foam uses smaller holes, adds very little weight, expands into voids and returns the slab to service quickly — real advantages on driveways and near structures. Mudjacking uses a heavier cementitious material at typically lower cost and remains a sound choice on thick slabs over stable ground.

How long does concrete leveling last?

It depends almost entirely on whether the cause was fixed, not on which material went under the slab. Where the void came from a one-off — a trench that consolidated, fill that settled — a lift can last a very long time. Where water is still washing soil out from under the slab, no injection material stops that, and the slab will drop again.

Can I drive on the slab afterwards?

Foam injection generally returns a driveway to service very quickly, often the same day, which is one of its main practical advantages. Mudjacking's cementitious slurry needs longer to gain strength. Get the specific number from your contractor for the material they are using rather than assuming, since it is one of the real differences between the methods.

Will the holes be visible afterwards?

Yes. They are patched, but they remain visible as small circles, and mudjacking's larger holes are more noticeable than foam's. On a plain broom-finished driveway this bothers almost nobody. On a decorative, stamped or coloured slab it is worth thinking about before you commit, because the patches will not match the finish.

Is leveling cheaper than replacing the slab?

Substantially, in most cases — that is the entire argument for it, along with keeping the concrete out of a landfill and not losing the use of the area for days. The comparison changes if the slab is deteriorated as well as sunken, because then you are paying to level something you will still be replacing before long.

Can a garage floor or a slab under the house be lifted?

Interior slabs and garage floors are commonly lifted, and foam is usually preferred there because of its low weight and small holes. A slab that is part of, or bearing on, the structure is a different question and needs a proper structural assessment first — lifting something that is carrying load is not a flatwork decision.