Concrete repair: what to know

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

What concrete repair is

Concrete repair fixes cracks, flaking surfaces, holes and sunken edges in slabs, steps and walls before the damage spreads. Most repairs also have a cause underneath, such as water, freeze and thaw, or a weak base, so a good repair starts with finding that cause.

Signs you need it

  • Hairline cracks have widened, or the two sides of a crack sit at different heights
  • The top layer flakes, pops or peels off in patches and exposes the gravel underneath
  • Water pools in a low spot on the slab or runs along a crack after rain
  • Rust-colored stains show up at cracks, which can mean the steel inside is corroding
  • A section of walk or driveway tilts toward the house or a low spot, pulling its joint apart
  • Chunks break off along an edge or around a drain, a step nosing or an expansion joint

What the pro does

  • Inspect the slab and the ground around it for water flow, sunken areas and rust stains that point to exposed steel
  • Chase out loose or damaged concrete to sound material, undercutting the edges of each patch so the repair locks in
  • Clean the crack or hole with a wire brush or grinder and blow out the dust, because dust blocks bonding
  • Fill narrow cracks with flexible crack filler or inject them with epoxy, and patch larger holes with a repair mortar
  • Correct the cause where it is practical, such as repacking a settled base or adding drainage away from the slab
  • Cure the repair under a moist cover or curing compound, then keep traffic off it until it hardens

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Every job is different, so we do not publish prices.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.

  • How many cracks and patches there are, and whether they are spread across the slab or concentrated in one spot
  • Whether water or settling caused the damage, since a leveling or drainage fix may have to come first
  • The depth of the flaking or the size of the hole, because deep damage needs more repair material and labor
  • Whether rebar is exposed or rusted and must be cleaned or replaced before the patch goes in
  • Surface type, since stamped, colored or exposed aggregate slabs need the repair textured and tinted to match
  • Access to the area and whether the damaged section can be reached without moving a fence, a vehicle or landscaping

What a written quote should spell out

  • The cause the pro found, such as water, base failure or freeze and thaw, and the fix that addresses it
  • The repair method for each crack or area, such as crack filler, epoxy injection or a full depth patch
  • The repair material named, and whether color and texture will be matched to the existing slab
  • How the damaged concrete is removed and who hauls the debris away
  • Any drainage or grade work, listed as its own line so it can be compared or deferred
  • Curing time and traffic restrictions for the repaired area

Questions to ask before you hire

  • What do you think caused this damage, and how did you confirm it?
  • Will the repair match the color and texture of my slab, and what happens if it will not?
  • Will you fill the crack or inject it, and why is that the right choice for this crack?
  • If you find rusted rebar under the damage, what do you do about it before patching?
  • Will you fix the water or the sunken base, or only the surface you can see?
  • How long must I keep the area closed while the repair cures?
  • Can I see photos of similar repairs you have done on older slabs?

Red flags

  • Recommends a surface coat or caulk over a crack without looking into why it formed
  • Patches over loose or crumbling concrete without chasing it back to sound material
  • Uses the same filler on every crack, whether it is hairline or moving
  • Promises the damage will not come back without checking the water flow or the base
  • Does not mention rust or exposed steel when the flaking runs deep along the bars

What you can do yourself

A homeowner can clean out and fill hairline cracks in a stable slab with flexible crack filler, which is a reasonable small job. Call a pro for cracks that are widening, sunken sections, flaking deeper than the top layer, exposed steel, or any repair that has to change how water flows. Wear eye protection and gloves when grinding or mixing repair mortar, since the dust and wet mix irritate skin and eyes.

Licenses and permits

Concrete repair is commonly done by licensed contractors, and larger structural or leveling work may need a permit in many areas. Check with your state or local licensing agency and your local building department before work starts, especially for steps, retaining walls or repairs that change drainage.

Concrete repair questions

Can you just fill the cracks and call it done?

Filler works for narrow, stable cracks, but a crack that keeps moving or is letting water under the slab will open again. A pro should check whether the crack is still moving and whether the slab is settling before recommending filler alone.

Will the patch look different from the rest of the slab?

A patch can be close in color and texture, but it is rarely identical, especially on older concrete that has weathered. Ask the pro to show a sample repair on a similar slab before the work starts.

Why does my concrete keep flaking?

Flaking, called spalling, usually comes from freeze and thaw cycles, de-icing salt, or water soaking into the surface and expanding. The repair has to stop that water or salt, or the new surface will flake as well.

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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