How to Repair Concrete in a Leaky Basement

During the construction of a new home, the foundation contractor will compact the soil, pour the concrete basement and then apply a sealant to the exterior walls to reduce the risk of leaks. Unfortunately, shifting soil can crack the basement walls, creating a leaky problem. Since water in the basement can lead to mold, it’s imperative to repair the concrete and prevent future leaks. The repair process you choose depends upon the type of cracks in your basement.

Things You'll Need

• Chisel
• Hammer
• Putty knife
• Concrete sealing compound
• Polyurethane foam (optional)
• Paint roller and pan
• Excavator (optional)

Instructions

Preparation

1. Stop or reduce the leaking as much as possible. Raise the soil grade around your home’s foundation to encourage water to drain away from the basement walls.

2. Inspect guttering for clogs that may be allowing rainwater to run over the guttering and into the crack between your basement walls and the yard

3. Stop watering plants near the foundation for a few days to reduce water drainage into the basement.

Sealing

1. Chisel away the edges of any cracks larger than 1/8 inch wide. A crack this large allows water to drain easily into the basement. Using a chisel and a hammer, carefully chip away at the crack until it is approximately 1/2 inch wide. Brush away all bits of loose concrete from the crack.

2. Apply waterproof concrete sealant to the crack with a putty knife. Work it deeply into the crack with the edge of the putty knife before smoothing off the crack’s surface with the flat end of the blade.

3. Roll on a waterproof sealer if you have leaky hairline cracks or if your concrete walls seep moisture. Unfortunately, this may indicate that the contractor did not seal the outside of your basement walls during initial construction.

4. Seal the inside of the concrete walls with a large-nap roller and a roller pan filled with an interior elastic sealant made just for concrete. Press the roller into the wall to work as much sealant as possible into the tiny cracks and holes.

5. Dig the soil away from the exterior of your basement and apply a thick coating of tar or concrete sealant. This is a last resort and it is expensive and time-consuming.

Tips & Warnings

• Contact a mold remediation contractor if you think mold is growing in you basement as a result of the leaks.

• Ask a contractor about installing interior drain tile in your basement.

• Dangerous radon gas may leak into the home if the basement has cracks.

References

• This Old House: How to Fix a Leaky Basement Wall
• Inspectopedia: Repair Cracks with Polyurethane Foam Injection
• Radon Seal: Make Your Wet Basement Dry