The structure of basement walls must be maintained; otherwise, even a small amount of water can damage building materials, cause mold and mildew, and render the space uninhabitable. Even tree and plant roots can find their way through holes in basement walls. As a result, one component of your waterproofing plan should be to repair cracks in the concrete walls before finishing your basement—or even for an empty but dry basement.
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.
- Plastic injection ports are inserted into the crack every 4 to 6 inches.
- The ports are sealed to the concrete with epoxy paste.
- An epoxy adhesive is spread over and beyond the crack, leaving the port tops exposed.
- 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.
- 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.
What You’ll Need
Equipment / Tools
- Putty knife
- Waterproof gloves
- Brush
- Heat gun (optional)
- Nylon or wire brush
- Scraping device
Materials
- Concrete crack filler
- TSP cleaning solution
Instructions
Clean and Dry the Concrete
Thoroughly clean out the crack and about 1 or 2 inches beyond the crack. Use either a nylon brush or metal wire brush, along with a TSP cleaning solution. Rinse. Dry out the crack and the surrounding area with a heat gun.
Clean and Dry the Concrete
Using a scraping device such as an old screwdriver or nail, scrape out the crack. Be sure to remove all loose debris, especially around the edges.
Scrape Out the Crack
Shake up or stir the crack filler. Add it to the crack. Try to press as much filler into the crack with the filler bottle as possible. Generally, though, the filler will sit on the surface (in the next step, you will press it in). Work in small sections. Complete one section of about 1 to 2 feet before moving onto the next section.
Add the Crack Filler
Put on a latex or latex-substitute glove. Much like pressing caulk into a crack, use your finger to press the concrete filler into the crack. Remove excess with your finger or with a cloth.
Press In the Crack Filler
Use the putty knife to trowel the crack filler further into the crack. Also, flatten the crack filler over the crack. Let the crack filler cure for at least 24 hours before painting.