How to Waterproof a Block Wall Basement

Leaking basement walls can cause the formation of mold and mildew. Waterproof your basement walls with with a sealer to protect them from floods and moisture damage. Waterproof sealers are available in a variety of forms, such liquid and paste. Depending on the type of sealer you purchase, you can apply it using basic household tools, such as paint brush or roller; for other types of sealers, you may be required to use sprayers or trowels.

  • Wall repair material
  • Water and mild soap
  • Bristled brush
  • Paint scraper or sand blasting
  • Block wall sealer
  • Paint brush, roller, sprayer or trowel
Repair any wall holes or cracks by mixing and applying a wall repair material such as an epoxy mortar specially designed for masonry repairs. You may need to clean large cracks and holes prior to applying the mortar mix.

Clean the walls with a mild detergent and water. Remove dust so that the sealer will correctly adhere to the wall. If the wall is painted, remove the paint using a sander, scraper or sand-blaster prior to applying the sealer; sealers are not designed to be applied over paint.

Mix the sealer according to the manufacturer's recommendations. There are a wide variety of sealers on the market, so follow the directions provided on the packaging for proper usage.

Apply the sealer to the bottom of the block wall and work your way up. Apply the sealer with a brush, roller, sprayer or trowel, depending on the type of sealer you are using. Make sure to apply an even coat of sealer over the entire area without stopping to prevent seams, which may allow leakage.

Follow the sealer manufacturer's recommended drying time to ensure a proper seal. Keep the area free of flying debris to avoid contaminating the sealer.

Apply another layer of sealer to the block wall following the previous steps.

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