If you are looking at cracks in the exterior walls of your basement, you are looking at cracks in your foundation. Fortunately, over 95 percent of foundation cracks do not create a threat to the integrity of the building, according to the website Basement Questions. Generally, the most they can do is to let water seep into the building. The cracks still need to be repaired. A frequently wet basement wall can encourage mold, mildew and fungus, which reduce indoor air quality. People often repair cinder block wall cracks with the same caulk they seal windows or fill gaps between tub and bathroom wall with. Such caulk will not hold.
Things You'll Need
- Safety goggles
- Protective gloves
- Warm water
- Stiff brush
- Dishwashing liquid
- Injectable concrete epoxy resin
- Epoxy resin injection gun
Chisel out the crack in such a way that you undercut it, creating a V-shape groove with the point of the V closest to the surface. Wear safety goggles and protective gloves. Use a chisel and a hammer. Make sure you chisel out the V-shape facing the right direction. If you simply make a V-shape in the concrete with the point on the inside of the crack, the repair materials will pop out.
Clean out the crack with a stiff brush to remove any loose material. Wash the concrete block adjacent to the crack with warm water mixed with a degreasing agent such as dishwashing liquid. Use 1 tbsp. of dishwashing liquid for every gallon of warm water. Rinse with clean water.
Inject concrete epoxy resin into the crack, beginning at the top and drawing the injection gun down along the crack to the bottom. Concrete epoxies expand as they cure, so they will fill the V you chiseled out and all of the adjacent pores in the concrete block. Unlike regular cement (which you should not use), the epoxies are formulated to be impervious to the alkaline chemicals in the concrete. They bond strongly enough to the concrete to withstand the weight of the water that could otherwise seep into the basement from the outside.