How to Finish a Limestone Basement

Slip on a pair of rubber gloves, respirator and safety goggles before creating a mixture of 1 tablespoon TSP, or trisodium phosphate, and 1/4 gallon lukewarm water in one of your buckets. Stir the warm water until the TSP is completely dissolved. Fill another bucket with plain water.

Dampen a plastic scrub brush into the TSP solution and work it into the limestone walls, cleaning in sections from the top of the walls down. TSP is a mild degreaser that effectively removes any stubborn grease, grime, efflorescence, chalking and other stains from the limestone surface without degrading the rock.

Dampen a rag with the plain water and wipe down the walls to remove the lingering TSP solution. Wipe down the walls with several towels to dry. Allow the walls to finish air-drying completely before continuing.

Apply the limestone sealant, which is available in several sizes at home improvement and hardware stores, with a paintbrush, working from the top of the walls down. Read the label to locate the limestone sealant that meets your needs, including the size of your basement, temperature and other environmental conditions. Continue to apply the sealant in a thin coating until the limestone surface is completely covered.

Allow the sealant to cure according to the package directions, or at least 24 to 48 hours, before applying a second thin coat. Open the basement windows or run a few box fans to speed up the drying process.

Inspect the walls after allowing the second coat to cure for 24 to 48 hours. If there are any noticeably bare spots, which will be dull or flaky, cover these areas with a thin coating of the product.