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Basement Floor Cracks: Why, What and How

Updated: Mar 17, 2023

Have you noticed cracks in your basement floor recently? No need to panic, this is actually a very normal part of the homeowner process. The problem with basement cracks is that it leads to potential moisture coming into your basement and eventually water. The good news is the cracks in basement floors are normal and repairable.

Why do basement floors crack?

The foundation of a home is well-built and yet it is still common to see cracks in the basement floor. Most times, the cracks are non-structural settlement cracks. The reasons basement floors crack vary but normally because of issues such as concrete shrinkage, the settling of the home, poor construction, and concrete curing or stress.

Improper drainage may also harm the foundation by excess amounts of water. As the water build-ups, it starts to increase unexpected amounts of pressure on the foundation that results in basement floors cracking. A few ways to improve drainage and avoid foundation floor cracks are:

  • Regularly cleaning out your gutters

  • Ensure proper landscaping and slopes at a distance from the foundation

  • Add a sump pump to help with any excess water drainage in the basement.

Types of Basement Floor Cracks and What They Mean

Cracks showing heaving are bigger problems that require immediate attention. Heaving is common in areas having clay soil. Heaving means the basement floor is actually expanding. In the clay soil areas, the soil becomes wet creating more pressure and cracking in the concrete floor.

How to resolve: Call a foundation repair professional contractor. They will level the sinking and the concrete floor, recommending the right solution.

Close-up of a cracked floor. The concrete slab may crack if the slab is less supported in the depression. Any uneven surface creates a tripping hazard.

How to resolve: Concrete floors in the basement should be leveled, if uneven. A high-density polyurethane formula helps to lift permanently and stabilize a concrete sinking slab. The polyurethane material levels the slab as it lifts and expands.

Keep an open gap between the floor and basement wall. The basement area where the floor and the walls meet is known as the cove joint and water seepage in this joint is a common problem. A small gap should be left between the walls and the floor so that when there is a rise in the groundwater level, the soil is saturated.

How to resolve: Sealing a gap is an effective solution as a basement waterproofing system. It helps to relieve hydrostatic pressure.

Large Crack. A crack in 1/8 inch or wider is a result of shrinkage. Though not a serious problem to the basement, it can allow moisture, water and radon to enter into the basement.

How to resolve: Any crack more than 1/8 inch must be sealed so that they do not seep through the basement floor.

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