How to Fix a Cracking Basement Floor: Video

Cracks in your basement floor can be alarming. You may wonder if they’re serious enough to warrant calling in an expert. Experts agree that every crack should be looked at by an experienced contractor; and any crack more than ⅛ inches wide should be sealed. Depending on the cause and extent of the crack, the fix might range from leaving it alone to extensive repairs.

Cracks in the basement floor are caused by poor construction, water damage, concrete shrinkage, curing, the home’s setting, and stress. The fixes include waterproofing, sealing, lifting, leveling, or resurfacing the floor. The cost of floor crack repairs ranges from $3 to $7 per square foot.

Let’s learn more.

Crack on the floor

How to fix cracks in a basement floor

A good number of the cracks on your basement floor are harmless. However, the others can be fixed as follows:

1. Cracks with heaving

When the soil beneath the basement floor expands significantly, it can lead to cracks with heaving (lifting). Common with clay soils, cracks with heaving result from the soil getting wet and exerting pressure on the floor from below. This type of crack needs immediate attention.

How to fix it

Call for a professional foundation repair contractor to assess and fix the issue. This isn’t one you can fix by yourself.

2. Cracks close to the cove joint

The cove joint is the area where the floor and wall of the basement meet. A small gap is left at this joint during the basement construction. However, hydrostatic pressure might force water through it especially when the water table rises such as during floods or the rainy season.

How to fix it

You may be tempted to seal off this gap but that’s a bad idea. Instead, install a basement waterproofing system to reduce the hydrostatic pressure. The system can be a combination of a sump pump and interior drain tiles.

3. Cracks that are ⅛ inches or wider

Hairline cracks ⅛ inches or narrower shouldn’t bother you since they’re as a result of normal expansion and contraction of the walls and floors. However, those larger than ⅛ inches should be checked and fixed by an expert since they can allow moisture, water and dangerous gasses like radon into the basement.

Radon mitigation, which takes many forms such as installing a radon detector, resealing the walls and floors of your basement, and installing fans to do away with the gas, costs between $1,000 and $3,500 or more.

How to fix them

Seal the cracks with a basement floor sealer. If you suspect them to be deeper than that, call for an expert to assess them before sealing them off. They might require more than simple sealing.

4. Cracks on sinking floors

Concrete slab floors can crack after the foundations settles. Part of the floor might sink thus creating an uneven floor. Besides being a tripping hazard, it’s ugly.

How to fix them

If the floor is uneven, it should be leveled out. A high-density polymer can be injected into the void below the sunken part of the floor to lift it up. This is permanent and is only done by experts.

5. Hairline cracks

Hairline cracks are tiny and below ⅛ inches and are caused by the shrinkage of the concrete as it dries up. Most hairline cracks are harmless but, as always, have them checked out by an expert before making a conclusion on them.

6. Flaking and spalling

In the construction phase of the basement floor, the top layer often loosens after drying, leaving flakes of dirt on it. This results from poorly cured or dried concrete mix. Although ugly, it’s harmless.

How to fix them

Either install waterproof flooring over the concrete or resurface it. You can also add flooring like linoleum, carpeting, or tile. Painting won’t work since it’ll keep flaking and removing the paint.

7. Perimeter cracks

Perimeter cracks occur where the concrete floor meets the foundation walls. As the floor and walls dry up after construction, the floor shrinks away from the walls, leading to these cracks. 

How to fix them

Basement perimeter cracks can be prevented by tying the concrete floor to the foundation wall with steel reinforcements in the initial construction stages. However, if they are already developed, you should seal them with an elastomeric caulking for interior masonry.

Are basement floor cracks dangerous?

Basement floor cracks are only dangerous when more than ⅛ inches wide. Such a crack can allow in water, moisture, gasses, and compromise the integrity of the basement. Even then, always have each small crack or flake checked since it might be more than surface-deep.

How to prevent basement floor cracks

The most important aspect when preventing basement wall and floor cracks, and generally preserving the integrity of your house, is controlling the drainage around it. Some of the ways to do so include the following:

  • Ensure the land around the house slopes (2% slope) away from the house.
  • Maintain your gutters to prevent damage and leakage into the foundation of the house.
  • Direct gutter water away from the house by extending gutter downspouts away from it.
  • Add a sump pump into the basement.
  • Properly seal the floor and walls of your basement to keep the water out.
  • Install drain tile around the foundation’s exterior to direct water into a sump bucket.

This way, you’ll have kept the foundation dry; preventing cracks in the process. Ideally, schedule routine checks on your basement to ensure it’s in good shape.

Frequently Asked Questions

Is it normal for basement floor to crack?

Most cracks in the basement floor are normal and don’t need repairs. Cracks in the basement floor won’t affect the integrity of the whole house since the basement floor doesn’t support the weight of the house.

Do cracks in the basement floor mean foundation problems?

Cracks on the floor, be it in the basement or other places in the home, may point to an issue with the floor. They result from many issues including uneven soil, improper construction, or the weight of the home.

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