Before you choose from the numerous basement sealants, you need to determine the source of any moisture in your basement. It is incredibly common for basements to begin taking on moisture 10 to 15 years after they are constructed. As many as 60 percent of basements will be wet during this timeframe, with as many as 33 percent experiencing mold and mildew issues. This moisture may be the result of condensation or could be caused by cracks in the foundation. The first sign of an issue is typically a musty smell many people automatically associate with basements. If your basement is finished without first applying the necessary sealant, the moisture will become trapped and can lead to mold and mildew growth.

A polysiloxane blend basement sealant will bond directly to the substrate to create a naturally water repellent surface. This type of basement sealer will repel any moisture and stop the growth of algae, mold and mildew. However, polysiloxane sealers still allow gases and vapor through, and the surface cannot be painted. This means as an interior sealant, this choice doesn't typically last as long as other options.

Another drawback is these sealants will only permeate about ¾ inches into the concrete, leaving much of the foundation unprotected. However, the sealant is UV resistant and typically has a long lifespan when applied properly.