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How to Fix Peeling Paint on Basement Cinderblock Walls

Kathryn Hatter

Cinderblock walls in the basement should keep the basement dry and tight against moisture for many years, although you may need to apply fresh paint periodically. If you notice areas where paint is flaking away from the wall, you must fix the peeling paint to ensure that the new paint will adhere properly to the rough surface.

Moisture often causes paint to peel off cinderblock.

Step 1

Scrub the surface of the cinderblock walls vigorously with the wire brush to remove all peeling and flaking paint.

Step 2

Sand the wall surface completely with the sandpaper to continue removing every area of loose paint. Continue working until no paint separates from the wall.

Step 3

Vacuum the wall surface well with the brush attachment of the vacuum cleaner to remove all dust.

Step 4

Examine the cinderblocks for cracks and pinholes. If you find hairline cracks less than 1/8 inch wide, you can cover these cracks without performing any preparation to them.

Step 5

Chip out a dovetail groove along the entire length of cracks larger than 1/8 inch wide. Use the chisel and hammer to gently chip away concrete on both sides of the crack. A dovetail groove has 45-degree angles that are narrower at the surface of the cinderblock and angle wider through the concrete at a 45-degree angle on either side of the crack. Chip carefully and slowly with the chisel and hammer to create a groove with the correct angle, making the space between the opening of the groove on the surface of the cinderblock about 1/4 inch wider on each side of the crack. Continue the dovetail groove along the entire crack.

Step 6

Mix the hydraulic cement patch compound in the bucket, adding about 3 ounces of water to each pound of compound. Stir well until the compound resembles thick putty. Mix only what you will use in about three minutes.

Step 7

Apply the patch compound to hairline cracks, pinholes and the dovetail grooves you created, using the putty knife. Fill these areas completely and smooth the surface with the putty knife. Allow the compound to set for the time indicated on the product label.

Step 8

Mix the concrete cleaner in the bucket, combining 1 part water and 1 part cleaning solution. Mix the solution well and apply it to the wall using the scrub brush. Allow the cleaner to sit on the wall for about 30 minutes and then scrub the wall thoroughly. Rinse the cleaner off with plain water and allow it to dry completely.

Step 9

Cover the floor with the drop cloth.

Step 10

Pour the waterproof paint into the paint tray. Load the 4-inch paintbrush and apply the paint around the perimeter of the wall carefully. Load the paint roller and apply the paint inside the painted perimeter, covering the cinderblock surface thoroughly. Allow the first coat of waterproof paint to dry completely and then apply a second coat using the same application technique.