How to Waterproof a Limestone Basement

Limestone, a sedimentary rock that is made from the discarded shells of marine organisms, is widely used to construct basement walls because of its durability and ease of installation. However, the stone’s naturally porous nature leaves many homeowners with “weeping” walls, making the space damp and unfit to store furniture or other belongings. Sealing the basement’s limestone walls is the most effective way to protect it and any items housed inside the space from damage and potential mold formation.

Rubber gloves
Safety goggles
Trisodium phosphate
Warm water
Plastic scrub brush
Kitchen sponge
Limestone sealant
Lambskin applicator

Instructions

- 1
  Slip on a pair of rubber gloves and safety goggles before creating a mixture of one part TSP, or trisodium phosphate, and five parts warm water. Stir the ingredients thoroughly to ensure the TSP powder is completely dissolved.
- 2
  Dampen a plastic scrub brush with the TSP mixture and begin to clean the limestone surfaces. Avoid using a mop to clean the walls, as this non-abrasive surface is not sufficient enough to remove any deep impurities, dirt, grime and mold growth.
- 3
  Rinse off the TSP mixture with a large, damp kitchen sponge. It’s crucial to remove any remaining TSP residue, as the mild degreaser will begin to degrade the limestone over time. Allow the limestone surfaces to dry completely before continuing.
- 4
  Apply a thin layer of the limestone sealant with a lambskin applicator. Using even back and forth motions, cover the limestone walls with the product. Allow the initial layer of sealant to dry according to the package directions -- at least eight hours.
- 5
  Apply a second and third layer of the sealant if recommended by the manufacturer. Allow the final layer to dry for at least 48 hours before inspecting the wall to check for any missed spots. Cover these spots with the lambskin applicator.

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