Cement floors can often crack from forces outside the homeowners control. Luckily, patching and repairing cement is a rather simple procedure, which any Do-It-Yourselfer can tackle. A local home improvement store should have bonding adhesive, vinyl reinforced patching compound, as well as cement fortifier, needed for larger cracks. For areas which are cracked due to tree roots or settling foundations, ask the home improvement center for any added ideas on continued maintenance, as the problem will likely persist in the years to come.
Step 1 - Preparing the Crack
Chisel out the area of the crack using the cold chisel and the hammer. The goal is to clean out the area where the crack is so that the patching compound can adhere to the solid cement. If the compound is added before the crack is cleaned, the broken and crumbling cement will adhere to the compound and then will fall apart further. The crack needs to be chiseled out at a backward angle, so that it becomes larger the further into the crack.
Step 2 - Cleaning the Crack
Use a dust mask and eye protection to protect yourself from cement debris. Clean the broken and crumbing bits from around the crack using a wire brush to sweep off edges. A power drill with a wire brush attachment can also be useful for stubborn areas or to make the job quicker. Fully sweep the dust and debris from the area. If the area is exceptionally dirty, use a hose to clean the cement. Any dirt will stick to the adhesive and be permanently stuck.
Step 3 - Adding Bonding Adhesive
Use a paintbrush to apply bonding adhesive all around the crack and the area. This bonding adhesive helps to hold everything together as the patching compound works. It is also helpful to be sure the surrounding cement stays together and does not begin to crumble. Be liberal with the bonding adhesive as it helps to keep everything together.
Step 4 - Using Patching Compound
For a small crack, use vinyl patching compound to fill the crack. With a trowel, slowly pack the crack with the compound. When the crack has been filled, be sure to mound the compound up at least an inch above the surface. Use the added compound to smooth and feather the edges of the out from the crack so that it is even with the surface of the other surrounding cement.
Step 5 - Large Cracks
Large cracks should be chiseled, cleaned and bonding adhesive added in the same way as smaller cracks. However, pour sand into the crack and then mix up a sand-cement mix. Add cement fortifier to the mix and fill the crack with the same added inch above. Smooth and feather the added cement to be even with the surrounding cement surface. A level can also be helpful to get the floor as smooth and even with the other areas of flooring.