What Causes Cracks in Your Garage Floor?

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No matter the quality of your garage floor installation, a pristine floor will eventually develop cracks. Concrete floors are guaranteed to shift and crack as the garage settles and develops wear. In many cases, garage floor cracks are not indicative of extensive structural overhauls.

Cracks in a garage floor may seem like a daunting repair job best reserved for professionals. While this may be the case if your garage has noticeably shifted, many garage floor cracks can be serviced with simple DIY techniques.

This article will guide you through the most common causes of garage floor cracks and the best repair methods. If you are still unsure of whether you are taking practical measures, follow up with a foundation repair specialist.

4 Most Common Causes of Cracks

Concrete garage floors are prone to cracking under temperature fluctuations and other stressors. Many of these are minor cosmetic cracks that are mitigated by smart floor design. Cracking is so common that floors are often equipped with contraction joints to manage and direct cracks.

There are four primary causes of floor cracks — shrinkage, settlement, installation and water damage.

1. Shrinkage

Cracks frequently occur due to natural shrinkage. After the concrete is poured, the concrete hardens in the curing process, causing it to shrink. A concrete floor for a standard 180 square foot single car garage could contract by over ½ inch.

As the concrete shrinks, small cracks will open in the floor. Even freshly poured concrete slabs will commonly have these cracks. These are normally superficial cosmetic defects that will not cause long-term damage.

2. Settlement

Over time, your garage, like your home, will shift and settle into the soil. This settlement can stress the floor, with pressure eventually creating cracks. These can range from minor to severe, with large cracks requiring close attention. 

Wide cracks and splits that continue to expand may go deep to the base of the slab. This creates an opening for water to seep in, potentially leading to further shifting and the risk of flooding. If you see large cracks with one section noticeably elevated above the other, you should immediately contact a professional.

3. Bad Installation

Poor or hasty construction could be the cause of garage floor cracking. The following are common building problems that create cracks:

  • Improper troweling or thin top layers. The top layers of concrete can dry out too quickly, creating extensive hairline cracking.
  • Poorly compacted base or insufficient gravel. Sections may drop under the weight of the concrete.
  • Lack of rebar or steel mesh reinforcement. This creates insufficient support to maintain the concrete’s weight.

4. Flooding/Underground Water Source

If your garage has inadequate drainage and water is allowed to collect, your concrete garage floor will likely be subject to considerable stress. Water that accumulates in the soil can freeze in the winter. This causes soil expansion that can put pressure on the concrete, eventually causing swelling and cracking.

Accounting for drainage is a critical component of the installation. Garage floors should slope down and away from the house to prevent buildup. The top of the floor should be elevated above the soil level to prevent full water penetration.

How Do You Fix Garage Floor Cracks?

1. Cut both sides of the cracks.

Using a hammer and chisel, cut back, or “chase”, the side of the crack. This ensures that you are breaking away loose edges, giving your filler a firm, solid area to hold onto.

2. Chip out the cracked concrete and remove it.

Pull out any small concrete chips, loose stones or debris. Use a wire brush and a ShopVac to remove even minor loose particles, allowing filler to only adhere to fastened surfaces.

3. Fill in the crack.

Self-mixing or epoxy concrete filler is a convenient choice for filling small cracks. If you have larger cracks, you may need to mix the filler yourself or add base materials. Applying concrete bonding adhesive to the sides of the crack may be necessary or it may need to be mixed directly into the filler. Always carefully follow the manufacturer’s instructions when applying any product.

4. Pour the resurfacer into the crack.

Once you have your floor crack filled, wait for the filler to cure. Apply a layer of concrete resurfacer to blend the top layers and create a seamless transition and barrier.

When to Call a Professional

Bulging and erosion in the floor around a crack can indicate substantial structural issues. Any shifts, uneven sloping or sides of cracks raised higher than the other are signs of extensive repair requirements.

In many cases, these more advanced repairs require the care of a professional. Contact a foundation repair specialist if you do find uneven cracks, sloping or water accumulation. You may need more than a simple patch job. Catching issues quickly and contacting an expert can end up saving you a ton of money and extra work.

Most garage floor cracks are simple cosmetic defects that will not take away from the sturdiness of your garage. By simply cleaning, filling and smoothing out the cracks, DIYers can complete seamless repairs. With larger or growing cracks, contacting a professional as soon as possible is critical to saving the structural integrity of your garage floor. If you want more information on proper garage floor maintenance, contact us today.

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