Yes. Terracotta clay tiles are treated with a protective layer of double boiled linseed oil and clear wax. Boiled linseed oil is called an impregnator; it is absorbed into the surface of the clay tile and forms a water-resistant seal. The linseed oil also protects the tile from staining during grouting. Terracotta clay tile floors need to have a layer of oil and wax applied once every three to four years.