How to Level a Garage Floor

By
Lee Wallender
Lee Wallender
Lee Wallender

Lee has over two decades of hands-on experience remodeling, fixing, and improving homes, and has been providing home improvement advice for over 13 years.

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Updated on 01/20/24
Reviewed by
Deane Biermeier
Deane Biermeier
Reviewed by Deane Biermeier
Deane Biermeier is an expert contractor with nearly 30 years of experience in all types of home repair, maintenance, and remodeling. He is a certified lead carpenter and also holds a certification from the EPA. Deane is a member of The Spruce's Home Improvement Review Board.
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Fact checked by
Sarah Scott
SS
Fact checked by Sarah Scott
Sarah Scott is a fact-checker and researcher who has worked in the custom home building industry in sales, marketing, and design.
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In This Article
Project Overview
  • Working Time: 2 - 4 hrs
  • Total Time: 1 - 2 days
  • Yield: Level low sections in garage floor
  • Skill Level: Intermediate
  • Estimated Cost: $50 to $100

An uneven concrete garage floor or one with depressions can be a concern, especially if it's an attached garage. The entire concrete slab might be off-kilter, causing water to flow toward the house or the garage door to no longer close properly. Or certain areas of the garage floor may dip or bow or display cracks.

You'll need to hire a specialist to correct a tilted concrete slab, but you should be able to fill depressions or bring down gentle peaks on your own.

3 Ways to Level a Garage Floor

  • DIY: Pouring concrete leveling compound over low sections of the concrete driveway will fill them in and prevent water from pooling. Fifty-pound bags of self-leveling concrete patch cost around $35 to $50 per bag.
  • Slab jacking with mud: A special slurry (called mud) is pumped under the slab to adjust the tilt. Mud jacking with slurry is less expensive than foam-based jacking because the source product is cheaper than foam.
  • Slab jacking with foam: Polyurethane foam instead of slurry is injected under the slab through holes. Poly-based slab jacking costs about four times more than slurry-based jacking.

Tip

Though costly, a major advantage of foam jacking over mud jacking is that the lighter weight foam avoids overburdening the soil with yet more weight.

What You'll Need

Equipment / Tools

  • Broom
  • Shop vacuum
  • Scrub brush
  • 8-ft. 2x4
  • Angle grinder with coarse grinding wheel
  • Pointed trowel
  • Caulk gun (if needed)
  • Plastic bucket
  • Paint brush (if needed)
  • Paint roller (if needed)

Materials

  • Self-leveling cement
  • Concrete oil stain remover or dishwashing soap
  • Concrete patch (if needed)
  • Bonding additive (if needed)
  • Concrete sealer or paint (optional)

Instructions

How to Level a Garage Floor With Leveling Cement

  1. Clean the Slab

    Sweep and vacuum the entire slab. Clean away any oil stains with a commercial concrete oil-stain remover, or with ordinary dish soap and a scrub brush. If stains cannot be removed entirely, abrading the area with a grinder will help the leveling cement adhere.

  2. Mark the Low Spots

    Move a straight two-by-four across the floor, looking for low spots beneath the straightedge. Identify the low areas with light pencil marks.

    Tip

    Few concrete slabs are completely flat. Dips and depressions less than 1/4-inch deep are usually not troublesome enough to warrant repair.

  3. Grind Down High Edges

    Use an angle grinder equipped with a coarse grinding wheel to forcefully abrade down any high edges, such as where the slab has cracked and sagged unevenly. Also, grind down any areas with stubborn stains. Use the shop vac to remove all traces of grinding dust.

  4. Repair Deep Cracks and Depressions

    If the vacuum has sucked out deep cracks that leave sizable voids, use non-shrinking concrete patch to fill these areas. Concrete patch is available both in premixed tubs and in caulk-gun tubes for application. Use a pointed trowel to force the patch material down into the crack to completely fill gaps.

    Allow the patching cement to fully dry and cure before proceeding. For most products, this requires about 24 hours.

  5. Prime the Area (Optional)

    If the leveling cement directions call for it, brush on a bonding liquid over the area to be filled with leveling cement. This should be done only where the leveling cement label directs you to do so.

  6. Mix the Leveling Cement

    In a plastic bucket, mix the leveling cement according to manufacturer's directions. The mixture should be a thick but pourable slurry. If so directed, add a latex or epoxy bonding liquid as you mix the leveling cement.

  7. Apply the Leveling Cement

    Slowly pour the leveling cement over the depression, and use the two-by-four or another long straightedge to screed over the area, ensuring a uniform, flat surface. There is usually no need to trowel the surface, as leveling cement is fluid enough to self-level into a smooth, uniform surface.

  8. Allow to Dry

    Allow at least four hours for the leveling cement to dry enough to walk on. Allow at least 24 hours if you plant to seal or paint the slab.

  9. Apply Sealer or Paint (Optional)

    Applying a fresh coat clear sealer to the entire garage floor is a good idea after the patch dries. Or, if the floor was painted, you can now paint the entire floor to blend in the repaired areas with the rest of the surface.

How Slab Jacking With Mud or Slurry Works

Mud jacking corrects the tilt of an entire concrete slab by pumping slurry (called mud) under the slab in key areas to correct the tilt.

  1. Technicians drill a matrix of holes, each about 1 to 2 inches in diameter, into the concrete slab.
  2. A slurry of sand, gravel, ash, and water is ​injected into the holes.
  3. Adjustments are made. Technicians make sure that the slab is supported in all areas. If one area gets too much push, it can crack the slab by forcing it upward too much. If one area gets too little slurry, it is left unsupported and can eventually crack and break.​
  4. It takes about one day for the slurry to cure to its eventual strength of about 2,400 psi.
  5. The holes are covered with patching cement.

How Slab Jacking With Foam Works

Foam injections are similar to slurry injections but are considered more effective because technicians can better predict the expansion of the polyurethane foam. The foam product is far lighter than mud, too. About 3 to 4 pounds of polyurethane ​is equal to 100 to 150 pounds of slurry.

  1. Holes that are slightly over 1/2 inch in diameter are drilled into select areas of the concrete slab.
  2. Hoses are inserted in the holes.
  3. The foam is slowly pumped under the slab.
  4. After a calculated amount of time, the foam expands to its maximum size.
  5. After the injections are made, the holes are covered over with patching cement.
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  1. How to Fix Low Spots on a Garage Floor. AAA Concrete Raising Company.