How to Repair Concrete Cracks

Concrete is a durable material, but it is not immortal. Temperature shifts, shifting soil, and moisture penetration inevitably lead to spiderweb cracks or long fissures that detract from the finish of your garage floor or driveway. Ignoring these minor fractures is a mistake because water will seep into the crack, freeze in winter, and turn a simple surface blemish into a structural nightmare that crumbles your slab from the inside out. Repairing concrete is less about heavy construction and more about proper preparation. If you don't remove the loose debris and oil residue, nothing you apply will stick, and you'll be repeating the job by next season. When done well, the patch blends into the slab, creating a seamless seal that prevents further water infiltration and keeps the surface level and safe.

  1. Remove Debris First. Use a hammer and a cold chisel to widen the crack slightly and knock out any loose, crumbling concrete. Use a stiff wire brush to scrub the interior, then vacuum out all the fine dust and debris until you reach solid base concrete.
  2. Scrub Away Oil. If the concrete shows signs of oil or grease staining, apply a concrete degreaser and scrub thoroughly with a nylon brush. Rinse the area with clean water and allow it to dry completely before proceeding to the next step.
  3. Pick Your Weapon. For hairline cracks, use a liquid concrete filler in a squeeze bottle. For wider cracks, use a masonry crack filler compound that can be applied with a caulk gun for better control.
  4. Pack It In. Apply the filler into the crack, working from one end to the other with a steady hand. Overfill the crack slightly, as the material will shrink as it loses moisture while curing.
  5. Smooth It Flush. Use a metal trowel to smooth the filler flush with the surrounding slab. Drag the edge of the trowel across the repair to scrape away the excess material while keeping the surface level.
  6. Let Time Work. Allow the patch to cure for at least 24 to 48 hours depending on the product label. Avoid walking or driving over the repair until it has reached its full hardness.