Laying Cement on a Crumbling Wall

Enlarge small cracks and undercut cracks and holes. Use a cold chisel and hammer to chip away at the edges of the gaps to make the patch areas at least 1 inch deep and larger at the bottom than at the top. Shaping the repair in this manner will help to secure the patch.

Brush loose material and debris out of the repair sites using a stiff wire brush.

Clean the area thoroughly. Use a strong stream of water from a hose or compressed air to remove any dust or dirt. This is necessary to ensure that the patch will be able to adhere to the old wall.

Apply a cement adhesive such as an acrylic resin by brushing it into the enlarged areas. You can also use a thin mixture of Portland cement and water. Although a cement adhesive will be most effective, successful repairs can be made by simply moistening the area thoroughly.

Prepare the concrete or cement mix for the patch areas. Add water and mix the patch cement according to manufacturer instructions.

Fill the holes and cracks with the patch mix using a pointed trowel. The cracks and holes need to be packed solidly.

Finish the surface of the patch. Smooth it with a wooden or metal float for a smooth finish. Otherwise, it might be feasible to make the patch blend with the surrounding old wall by trying to duplicate the finish with a broom or other tool.

Cover the patches with plastic sheeting. Keep the area covered for about five days, lifting the sheeting once per day to moisten the repair site. Maintaining this level of moisture will permit the patch to cure properly.