How Do I Repair Cracked Block Walls in a Basement?

Fixing cracks in basement block wall is easy.

Contractors and homeowners often use concrete blocks as the primary building material for basement walls. Concrete blocks offer durability and strength to support the house. Repetitive freeze and thaw of the surrounding soil may cause some concrete blocks to crack. Once cracks are present in concrete blocks, the chance for mold growth increases as moisture makes its way into the basement. With regular repair and maintenance, you can easily fix cracks in concrete blocks.

Things You'll Need

• Cold chisel
• Hammer
• Shop vacuum
• Portland cement
• 2 buckets
• Water
• Paintbrush
• Pointed trowel
• Stiff-bristled broom
• Plastic sheet
• Duct tape
• Spray bottle filled with water
• Wire brush
• Putty knife

Instructions

Repairing Larger Cracks

1. Obtain a cold chisel from your hardware store if you don't have one in your tool box. A "cold chisel" is a chisel made of hard, tempered steel and used by blacksmiths to cut cold metal. It is also useful in masonry work for chipping brick or concrete.

2. Use your cold chisel and a hammer to undercut the crack. To undercut means to widen the crack and make the bottom of the crack wider than it is at the surface. This will add strength to your repair.

3. Turn on the shop vacuum, and suck away all loose concrete debris and/or dirt from the crack and surrounding wall.

4. Pour a small amount of Portland cement into a bucket, and mix water into the cement until it has a creamy consistency. Dip a paintbrush into the Portland cement mixture, and brush a thin layer into the crack area.

5. Force ready-mix concrete patch into the crack with a pointed trowel. Smooth the concrete patch with the flat edge of the trowel to match the surrounding block wall.

6. Tap a stiff-bristled broom over the patched area to mimic the texture of the surrounding wall.

7. Cover the patched area with a piece of plastic sheet. Duct tape around all the edges of the sheet to seal out air.

8. Peel back one side of the plastic sheet, and use a spray bottle filled with water to mist the area lightly. Re-cover the area with the plastic sheet, and seal with duct tape. Repeat this procedure one time per day, for five days.

Repairing Hairline Cracks

1. Clean the crack area with a wire brush to remove all loose dirt and concrete debris. Spray the small crack with water, using a spray bottle to moisten the area. Repeat this process for three to four hours to keep the concrete moist.

2. Pour Portland cement into a bucket, and add water until the mixture resembles thick paste.

3. Dip the putty knife into the cement mixture until you enough to cover the crack in the concrete block wall. Push the cement into the crack as firmly as possible to force as much of the mixture as you can into the crack. Use the flat edge of the putty knife to smooth the cement mixture even with the rest of the concrete block wall.

4. Allow the cement mixture to dry for two hours, and then begin curing the repaired area. Cure the area by taping a piece of plastic sheet over the area you just repaired. Seal all the plastic sheet edges with duct tape.

5. Uncover one side of the plastic sheet and mist the area with water. Cover the area again with the plastic sheet. Repeat this process for five days, one time per day.

References

• Aubuchon Hardware: How to Repair Concrete