Concrete leveling: what to know

What the job involves, what changes the price, and what to ask a pro.

What concrete leveling is

Concrete leveling raises a sunken slab back to level by injecting foam or grout beneath it through small holes, filling the voids that formed as the soil under it washed out or compacted. It is used on driveways, sidewalks, patios and pool decks when the slab has dropped but is still in one piece.

Signs you need it

  • A slab has dropped at one edge, creating a lip or a trip hazard where it meets the next piece
  • Water collects in a low spot on the slab, and the drop has moved the surface out of its drainage slope
  • The gap between the slab and the house, a curb or a step has widened as the slab sinks
  • The slab rocks or cracks under a vehicle or foot traffic, which can mean there is a void underneath
  • Downspout water runs under a walk or drive and has washed out the base
  • A pool deck or patio has settled away from the pool edge or the house wall

What the pro does

  • Survey the slab and mark the low points, the joints and the cracks to plan the injection holes
  • Check the soil and the drainage that caused the settling, since leveling does not fix water flow by itself
  • Drill small holes through the slab at set points, typically sized for the injection nozzle and kept clear of rebar
  • Inject polyurethane foam or cementitious grout beneath the slab in controlled amounts, lifting it in steps
  • Watch the lift in real time, stopping at the point where the slab is flat and the joints line up
  • Patch the injection holes, clean up the surface and let the material cure before the slab takes load

What changes the price

Every job is different, so we do not publish prices. These are the things that move the quote up or down.

  • Total area and number of sunken sections that have to be lifted
  • The amount of lift needed, since a slab that has dropped far needs more material and more passes
  • The type of material used, such as expanding polyurethane foam or cementitious grout, and what each suits
  • Whether the cause of the settling, such as water flow or washed-out soil, must be fixed as part of the job
  • Slab thickness and condition, because cracked or broken pieces may not lift as one solid slab
  • Access to the holes and any landscaping, fences, stairs or walls that the rig and crew must work around

What a written quote should spell out

  • The areas to be lifted, with the expected lift measured and the method named
  • Material type used, including whether it is foam or grout, and why it was chosen
  • Number and placement of injection holes and the patch method used afterward
  • Any drainage or grading work, listed separately so the customer can decide on it
  • Cure time and when the surface can take vehicles and foot traffic again
  • Warranty terms, including what happens if the slab settles again in the same area

Questions to ask before you hire

  • What caused the sinking, and will you fix the cause or only lift the slab?
  • Which material do you use, and why is it the right choice for my soil and slab?
  • How much lift do you expect, and how will you check that it stays level?
  • Where will the injection holes go, and how will they be patched?
  • How long before I can drive on the slab after the lift?
  • What is your warranty if the slab settles again?

Red flags

  • Lifts the slab without checking where the water is coming from or where it will go
  • Says the slab will lift as one piece even when it is cracked into pieces
  • Injects material in one spot without monitoring the lift at the other joints
  • Gives a warranty without stating what the settling warranty covers
  • Works in weather that will freeze the grout or prevent the foam from curing

What you can do yourself

A homeowner has little safe room to do this work, because it uses high-pressure injection equipment and materials that expand and cure fast. Call a pro for any sunken slab, since the wrong pressure or placement can crack the slab further. Polyurethane foam and grout can irritate skin and eyes and give off fumes, so use gloves, eye protection and good ventilation if you are near the work.

Licenses and permits

Slab leveling is commonly done by licensed contractors, and many areas do not require a permit for a leveling job alone, but structural or drainage changes may need one. Check with your state or local licensing agency and your local building department before work starts.

Concrete leveling questions

Will leveled concrete stay level?

It can, but only if the cause of the settling is fixed. If the soil keeps washing out or the drainage keeps sending water under the slab, the slab can sink again, so ask the pro what they have done about the cause.

Is foam or grout better for leveling?

Foam is lighter and cures fast, while grout is heavier and suits some soils and slabs better. The right material depends on the soil, the slab and the load, so ask the pro why they recommend one over the other.

Will the holes show after the lift?

The injection holes are small and are patched, but the patches are usually visible up close. Ask the pro to match the patch color and texture, and to show samples from earlier jobs.

About this guide

This national guide is written and checked by infinibell. Rules and conditions differ by place, so local pros are credited on guides for the cities they serve, not on national ones.

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