How to Repair Cracks in a Concrete Wall

Cracks in concrete walls, such as basement walls, can quickly develop into larger cracks and can let moisture through.

Basement walls need to maintain their structure; otherwise, even the smallest amount of water that comes through can rot building materials, create mold and mildew, and make the space uninhabitable. Even tree and plant roots have a way of finding their way through basement wall cracks. So, before finishing your basement—or even for an uninhabited but dry basement—one component of your waterproofing plan should be to repair cracks in the concrete walls.

Basement Wall Crack Repair Basics

Basement wall crack repairs fall into either of two categories: non-structural or structural repairs. Non-structural repairs, the focus of this guide, rehab the appearance of the concrete wall, prevent moisture infiltration, and slow further cracking. Structural repairs patch the wall together again so that it is as strong or even stronger than its original condition.

Non-Structural Concrete Wall Repairs

Cracks in concrete walls can be repaired with a liquid or paste elastomeric compound. The compound is squirted into the crack with a bottle or forced into the crack with a putty knife.

Cracks up to 1/2-inch wide and 1/4-inch deep, either interior or exterior, can be repaired this way. This compound can usually be painted over with latex-based paint if desired.

Easy, inexpensive, and do-it-yourself-friendly, the main purpose of this concrete repair is to block water from seeping into the basement. It will help to prevent the edges of the crack from further chipping away, but it will not prevent the wall from cracking or splitting apart.

Structural Concrete Wall Repairs

Concrete walls that need to be structurally sound can be repaired with a low-pressure crack injection method. The aim is to bond the concrete together again, as well as prevent water from seeping through.

1. Plastic injection ports are inserted into the crack every 4 to 6 inches.
2. The ports are sealed to the concrete with epoxy paste.
3. An epoxy adhesive is spread over and beyond the crack, leaving the port tops exposed.
4. An epoxy or urethane bonding agent is slowly inserted into the crack, starting from the bottom port and working up to the top. With the ports capped off, the epoxy adhesive acts as a shield to force the bonding agent into the crack.
5. After 24 to 48 hours, the epoxy is chipped away and the ports are cut or broken off of the wall.

While this is a highly effective method, it is not a do-it-yourself project. It should be done by foundation repair technicians.