How to Repair Concrete Cracks Under 1/8 Inch

Home basement walls, foundations and garage floors are composed of concrete for durability and stability. Moisture, extreme temperatures and structural settling can cause hairline cracks under 1/8th inch in a concrete surface. Untreated cracks in a foundation can eventually widen. More moisture can seep through the cracks and encourage mold and mildew. Promptly repair concrete hairline cracks under 1/8-inch to preserve a home's appeal and value.

• 1

  Scrub the cracked concrete with a wire brush to loosen stubborn dirt, grime and debris. Vacuum the crack with a shop vacuum attachment to remove the loose debris. Operate the shop vacuum according to the manufacturer's directions.

• 2

  Fill a plastic bucket with 1 gallon of warm water and 1 tsp. of liquid dish soap. Scrub the crack and surrounding concrete with the soapy solution using a nylon scrub brush. Remove any remaining dirt particles, oil and residue to ensure that the crack and surrounding concrete are completely clean.

• 3

  Dampen a clean cloth with warm water. Wipe the crack and surrounding concrete with the damp cloth to rinse away the soapy solution. Thoroughly dry inside the crack with the shop vacuum. Wipe the surrounding concrete with a clean towel to ensure that the area is completely dry.

• 4

  Cut a tube of epoxy concrete filler at a 45-degree angle with scissors. Follow the manufacturer's directions on the product label.

• 5

  Squeeze the epoxy filler into the crack. Slowly move along the length of the crack to prevent gaps.

• 6

  Allow the epoxy filler to cure for five minutes. Apply more concrete filler to areas of the crack where the existing filler has sagged or settled.

• 7

  Smooth the surface of the crack with a trowel to blend the repair with the surrounding concrete. Let the repair cure overnight.

• 8

  Repeat the patching process if the epoxy filler is sagging or gaps are present in the crack. Let the repair cure overnight.

• 9

  Apply three separate coats of polyurethane sealant to the affected concrete, using a roller brush. Allow each coat of sealant to dry according to the manufacturer's directions.