How to Waterproof a Cinderblock Wall

Written by larry simmons
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How to Waterproof a Cinderblock Wall
A breeze block wall, with many of its largest moisture-friendly pores visible. (block wall image by Irina Kodentseva from

Concrete products, though strong and durable, are porous in nature, and as such require waterproofing to prevent a build-up of moisture in the material that can lead to the development of cracks or flaking. Waterproofing a breeze block wall is essential, especially when the wall is in a moisture-rich environment. Waterproofing breeze block is not a difficult process. You can apply a concrete sealant to the block surface, allowing the sealant to penetrate and block the pores on the blocks that would otherwise allow moisture through. Upon completion, your new seal will last years, easily repelling the damaging water from its surface.

Skill level:

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Things you need

  • Laundry soap
  • Bucket
  • Sponge
  • Scrub brush
  • Dust sheet
  • Masking tape
  • Masking paper
  • Misting spray bottle
  • Hand pump sprayer
  • Concrete sealant
  • Low-nap paint roller
  • Extension pole

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  1. 1

    Clean the surface of the breeze block wall with a mixture of laundry soap and hot water. Fill a bucket with the hot water and then add laundry soap until suds begin to develop. Remove any dirt or debris from the blocks with the mixture, using a damp sponge or scrub brush. Rinse the mixture from the blocks with clean water and then wait for the blocks to dry before continuing.

  2. 2

    Cover the floor along the base of the wall with a dust sheet and mask off adjacent surfaces to prevent the sealant from spreading beyond the confines of the breeze block wall.

  3. 3

    Use a spray bottle filled with water to lightly dampen the surface of the breeze blocks. The water reduces surface tension on the blocks, aiding in sealer penetration.

  4. 4

    Fill a hand pump sprayer with sealant and then spray the sealant onto the breeze block wall, creating a wet-looking film. Apply the sealant using a low-nap paint roller equipped with an extension pole to reach the top of the wall. Roll the sealant onto the blocks working in rows along the length of the wall from top to bottom. Overlap each row by about 50 per cent to ensure complete coverage without any gaps between rows. Wait 30 minutes for the sealant to begin to dry.

  5. 5

    Apply three more coatings of sealant onto the blocks. Multiple coats are necessary to compensate for the larger pores found in breeze blocks compared to other concrete building materials. Wait six hours for the final coat to dry.

  6. 6

    Spray the wall again with water, dampening it. Scrub the blocks with a wet scrubber to remove any residue of the sealant on the wall's surface. The sealant inside the pores of the blocks will provide the waterproofing needed for the wall.

Tips and warnings

  • Remove any excess sealant due to overspray with a wet cloth immediately to avoid the sealant binding to surfaces other than the breeze blocks.

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