The Difference Between Types Of Grout By: Bruce Mendes | - Grout is the material that fills the joints between tiles. Grout can be water-resistant. However, water or other liquids, will most likely penetrate the joint and reach the backing. The best thing is to ALWAYS seal your grout and it is a maintenance issue to be done every 2 to 3 years. There are two major classifications of grout: Portland Cement Grout and Epoxy Grout.