SEAL-ONCE CONCRETE & MASONRY WATERPROOFER is a deep penetrating , nano technology based waterproofer for exterior and interior Concrete & Masonry Surfaces that are located above grade and have not been previously sealed. Seal-Once is water based, odorless, and non toxic. Seal-Once Concrete & Masonry Waterproofer seals water out. A One Gallon Pail of Seal Once will cover 100 SF of concrete or masonry surface with the recommended two coat application.