Fixing Cracks in Basement Floors

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  • 8-24 hours
  • Intermediate
  • $60-250
What You'll Need
Dust pan
Circular saw with diamond blade
Foam backer rod
Concrete sealer
Safety glasses
Face mask
Work gloves

Although it may seem daunting, repairing cracks in your basement floor is something you can do without going to the expense of hiring a professional. If you find cracks in the concrete of your basement, don’t panic. These cracks are part of the natural drying process for concrete. As it dries, the concrete begins to shrink. The stress released by the shrinking process causes the cracks. A good contractor will take measures to do as much as possible to eliminate the potential for cracks in a foundation, but when it occurs, it is something you can repair by following these six steps.

Step 1 - Repair Cracks ASAP

If you find cracks in your basement concrete, it’s important to repair them as soon as possible to prevent water from seeping into the cracks. Even if you don’t see signs of moisture in the cracks, it’s still important to repair them. Eventually, water will begin to seep through them, producing mold which could create health issues your family.

Step 2 - For Small Cracks, Clean the Area First

If the cement cracks you have found are small, hairline-type cracks, begin your repair process by merely sweeping and cleaning dirt and debris away from the area. Forced air can blow out any debris.

Step 3 - Chisel Loose Concrete for Larger Cracks

cracks in cement

If your cracks are fairly large, chisel all the concrete that is loose around the crack. For cracks that exceed 1-inch in width, place your chisel at the edges of the crack and use a hammer to strike the chisel. Chip away .25-inches from each side of the concrete. Doing will ensure there is no loose concrete along the edges of the crack.

Step 4 - Groove Crack Sides

Use your diamond blade circular saw to cut a dovetail groove on both sides of the crack. Once the grooves have been cut, clean the area of all the dirt and debris.

Step 5 - Fill Larger Cracks With a Foam Backer Rod

sealing a crack in cement

If your crack contains a large empty space, you will need to insert a foam backer rod, which you can pick up at your nearest hardware store, to fill the crack. Prior to installing the foam backer rod, fill the void with concrete sealer. For small cracks that don’t require a backer rod, you will need only to fill the crack with several applications of concrete sealer.

Step 6 - Fill Cracks with Liquid Urethane

Inject liquid urethane directly into the crack or cracks. As the urethane is injected, it begins to foam and expand to completely fill the inside of the crack. It also makes the crack moisture proof, preventing water from seeping into the crack at some future date. Although there are hydraulic cement products on the market that will fill your crack, using these products will only temporarily repair your cracks. You should avoid using this type of product if you want a permanent repair.

WARNING: Some urethane products are toxic to touch or breathe in, so read the urethane container's ingredients and instructions carefully. For safety, wear gloves and a face mask and safety glasses while using the urethane.