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How to Repair a Crack in a Concrete Garage Floor

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Are you dealing with a crack in your garage floor? Garage floor cracks aren’t all the same. Some are merely unsightly, while others can indicate structural damage–but how can you tell which is which? In this article, we’ll review the most common causes of garage floor cracks, the difference between structural and non-structural cracks, how cracks in a garage floor are repaired, and more.

What Causes Cracks in a Concrete Garage Floor?

Cracks in a concrete garage floor are usually caused by shrinkage during the concrete curing process (non-structural cracks) or differential foundation settlement (structural cracks).

Cracks in a concrete garage floor are usually caused by shrinkage during the concrete curing process (non-structural cracks) or differential foundation settlement (structural cracks).

Cracks Caused Shrinkage During Concrete Curing

Non-structural cracks in a concrete garage floor are typically caused by shrinkage during concrete curing. Concrete shrinks as it dries and cures, and when it does, it can cause small cracks on the garage floor’s surface. These types of cracks are usually not a cause for concern, since they do not affect the structural integrity of the garage floor. They are often considered a normal part of the curing process.

Cracks Caused By Differential Foundation Settlement

Structural cracks in a concrete garage floor are usually caused by differential foundation settlement. In other words, the problem is not with the garage floor, but with the garage’s foundation. Differential foundation settlement occurs when the soil underneath a foundation compresses or shifts, causing the foundation to settle unevenly into the ground. The best way to explain differential settlement is via an illustration:

Differential foundation settlement occurs when the soil underneath a foundation compresses or shifts, causing the foundation to settle unevenly into the ground.

Differential settlement places a lot of stress on the floor and can cause it to crack. Structural cracks are serious because they indicate foundation damage.

How to Determine the Cause of a Crack in a Concrete Garage Floor

While it can be challenging to determine the cause of a crack without professional assessment, some signs can help you decide whether or not it might be a structural problem.

How Wide Is the Crack?

If the crack is less than 1/8 inch, it’s likely a non-structural crack that is probably caused by shrinkage. As noted above, these cracks are generally cosmetic and won’t compromise the structural integrity of your garage floor. However, if the crack is wider than 1/8 inch, this may be a sign of a more serious issue.

Where Is the Crack Located?

Examine the location of the crack. If the crack is isolated and not near the edge of the garage floor, it may be a shrinkage crack. Cracks that extend across the width of the garage floor are likely structural in nature.

Is the Crack Getting Bigger?

Consider the progression of the crack. If the crack has remained the same size and shape for an extended period, it’s likely a shrinkage crack. However, if the crack has widened or multiple cracks are appearing, then it could be a sign of a more serious issue.

Is One Side of the Crack Higher than the Other?

These cracks are highly indicative of structural damage. Contact a professional right away and ask for an inspection.

To be safe, have a professional inspect the crack to determine the cause and provide you with the appropriate repair solution. It’s important to address structural issues promptly to avoid further damage and a more expensive repair.

How to Repair a Crack in a Concrete Garage Floor

When repairing cracks in a concrete garage floor, it is essential first to identify the cause of the crack, as this will determine the appropriate repair solution.

Repairing Shrinkage Cracks

If the crack in the garage floor was caused by shrinkage, then epoxy injection is typically an effective solution. Epoxy injection involves the injection of a specially formulated epoxy resin into the crack, which solidifies and fills the void. This not only repairs the crack, but also strengthens the slab. Epoxy injection is ideal for hairline or small cracks that have not affected the overall stability of the slab.

Repairing Cracks Caused by Differential Foundation Settlement

If the crack results from differential settlement, underpinning using piers is the most common solution. Underpinning involves installing piers beneath the foundation to stabilize, lift, and level it. This often causes the cracks to close. Foundation piers come in various types (including push, helical, and slab), and selection depends on the job’s specifics. For more information, see our article Underpinning A House: The Ultimate Foundation Settlement Solution.
Polyurethane Injections are also an effective repair method for differential cracks that are found in your garage, if your garage is a floating slab. A floating slab means that the garage floor concrete was poured independently of the foundation of your garage. Typically you can tell if this is the case by looking at the perimeter wall of your garage, and if the concrete holding up your walls is higher than your garage slab, then more than likely, your garage slab is a floating slab.

How to Help Prevent Foundation Issues

Fortunately, there are some things you can do to help prevent differential foundation settlement and a costly repair. Note that most of these involve controlling groundwater around the foundation. This is because–believe it or not–most foundation problems are caused by excess moisture in the soil.

Prevent Foundation Issues

  • Regrade your yard, if necessary, so that it slopes away from the foundation for proper drainage. A yard that slopes toward the house can cause water to pool around the foundation, leading to damage over time.
  • Install downspout extensions. Downspouts that are too short can deposit water directly onto the ground around the foundation. Installing downspout extensions will direct water away from the foundation and help prevent damage.
  • Clean your gutters regularly. Clogged gutters can cause water to overflow, run down the side of the house, and soak into the ground around the foundation. Gutters should be cleaned at least twice per year.
  • Install a drain tile system. This will collect excess groundwater, channel it into a sump pit, and then eject it away from the foundation.
  • Keep large trees away from the foundation. Some trees have root systems as wide as their canopies. If the roots invade the ground under the foundation, they can cause a lot of trouble. Trees should be kept at least 50 feet away from the foundation.

If you’re concerned about a crack in your concrete garage floor, contact us today to schedule a free evaluation and receive a repair estimate. We serve Southern California, Arizona, and Nevada.


Brian Dalinghaus

Brian is one of the Co-Founders of Dalinghaus Construction. He has been in the foundation repair industry since 2005. During his career, he has been associated with helping over 4,000 homes and structures throughout California and Arizona.

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