Skip to main content

How To Foam Cracks in a Foundation

Is your foundation a little shaky? Fix those unsightly cracks yourself and save yourself thousands of dollars in foundation damage and repairs.


  • Step 1: Attach the wide end of the hose assembly to the mixing tip and the small end of the hose assembly into the lowest port in the crack.
  • Step 2: Place the polyurethane foam cartridge into the caulking gun and place the remaining mixing tip onto the end of the cartridge.
  • TIP: Water should pour out of the other ports below to indicate that they are not blocked by epoxy. The water serves as a catalyst for the polyurethane foam.
  • Step 3: Squeeze the foam into the crack slowly, allowing time to fill the crack, until foam begins to pour out of the port above it. Plug the port with a cap and move to the next port.
  • Step 4: Repeat the process at each port and allow foam to cure for at least three hours.
  • FACT: The first reinforced concrete high-rise building, the Ingall's Building, was built in Cincinnati, Ohio, from 1902 to 1903.
  • Step 5: Remove the ports after the foam is dry by hitting them with a hammer. You can now rest easy that your weather proofing and insulation work will keep your belongings safe and dry.
  • Step 6: Pour 1 to 2 cups water into the crack using the top port by filling the hose assembly.
  • Step 7: Allow the epoxy to cure overnight for at least four hours.
  • TIP: If any water is present, wait until it is dry, or use a hair dryer to remove any moisture from the crack surface.
  • Step 8: Dust off the crack and make sure it is dry.
  • Step 9: Put on latex gloves. Put the epoxy cartridge in the caulking gun and put one of the mixing nozzles on the end of the cartridge. Put a small amount of epoxy on a scrap piece of cardboard and use a trowel to mix.
  • Step 10: Place a small amount of mixed epoxy onto the bottom of the uncapped port base. Insert the port into the base of the crack and repeat with another port every 8 inches along the crack.
  • Step 11: Apply the mixed epoxy to the surface of the crack using the trowel about 1/8 inch thick and 1 inch wide.
  • TIP: Make sure that the epoxy does not block the opening in the port base. This is where the polyurethane foam will be inserted into the crack.
  • Step 12: Put down drop cloths if repairing foundation walls. Clean the crack with a wire brush to remove any loose concrete, dirt, or paint.

Popular Categories