How to Seal a Cinder Block Garage Wall

Sealing a cinder block wall protects it from moisture.

A cinder block wall – commonly found in basements – is a durable structure made of concrete, but it is not impervious to moisture. Cinder blocks are porous, so water easily seeps into the blocks, which can cause cracks, spalling, mildew and other damage over time. Sealing a cinder block wall with waterproof sealer protects it from moisture and increases the longevity of the surface.

Things You'll Need

• Concrete patching compound
• Putty knife
• Scrub brush
• Dish soap
• Rags
• Paint stirrer
• Waterproof concrete sealer
• Paint tray
• 3-inch paintbrush
• Medium nap paint roller

Instructions

1. Repair any holes or cracks in the wall using a concrete patching compound. Spread the compound over the cracks or holes with a putty knife until it is packed into the spot and smoothed out flush with the rest of the wall. Allow the patch to dry completely as directed on the packaging.

2. Clean the cinder blocks with a scrub brush and warm, soapy water. Rinse the wall thoroughly with rags and clean water. The surface must be free of grease, dirt and other grime that can interfere with the sealer adhering properly. Allow the wall to dry completely.

3. Stir the can of waterproof concrete sealer with a paint stirrer. Don’t shake the can to mix it up as this can cause air bubbles. Pour the sealer into a paint tray.

4. Dip a 3-inch paintbrush into the sealer. Brush the sealer along the perimeter of the wall, as well as into the joints of the blocks. Apply the sealer thinly to the wall rather than globbing it on.

5. Coat a medium nap paint roller with sealer. Roll the sealer lightly onto the rest of the wall. Overlap each roller stroke to ensure adequate coverage.

6. Let the first coat of sealer dry completely according to the manufacturer’s recommendation. Apply a second coat of sealer to the cinder block wall in the same fashion.

Tips & Warnings

• Some sealers require the wall to be dampened with water prior to application. Read the instructions on the can of sealer to find out whether this is recommended.

• If the cinder block wall is painted, the sealer may not adhere properly. Refer to the manufacturer’s instructions as to whether the paint needs to be sanded off before applying sealer.

References

• Home Water and Moisture Problems; Gary Branson
• Concretesealertips.com: How to Apply Concrete Sealer