How to Waterproof Basement Walls From the Inside

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Things You'll Need

  • 6-Inch Masonry brush

  • Concrete block sealer

  • Paint roller and pan

Image Credit: Jupiterimages/liquidlibrary/Getty Images

Basement walls are almost always built using masonry materials like concrete or concrete block, and while these materials are generally stronger than others, they are porous and can absorb moisture from surrounding soil. The absorption of moisture from the soil can lead to water damage and an effect known as efflorescence (sodium stains). The best way to prevent this is sealing the exterior foundation walls, but this can prove to be an extensive task once the structure is complete; sealing the inside of the walls is the next best prevention method and is a straightforward task.


Step 1

Clean any loose dust and debris from the wall using the 6-inch masonry brush.

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Step 2

Gently pour the concrete block sealer into the paint roller pan and soak the roller.

Step 3

Evenly apply the sealer to the wall using the paint roller.

Step 4

Allow the sealer to dry; refer to sealer packaging for drying times and additional applications/coats and act accordingly.


Concrete block sealer can be harmful if inhaled; when working working in confined spaces like basements, provide proper ventilation. Refer to sealer packaging for safety precautions and warnings.


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