Cement-based grout is the most widely used type. It comes in two different formulation s— unsanded and sanded. The latter is preferred when joints between the tiles are 1/8-inch wide or more. Unsanded grout is made of cement and additives that promote drying. It is used on ceramic and marble wall tile installations. Sanded grout takes approximately 24 hours to dry. When dried, it is as hard as cement, but is very porous and subject to staining. Because of this property, a latex additive is sometimes added to the mixture, which partially retards the porosity. Latex additives also help prevent mold and mildew. To prevent staining, sealant is usually applied to all types of cement-based grout.
Epoxy grout is a two-part, waterless material manufactured of epoxy resins and a hardener. Silica filler and pigments are also present in many formulations. These grouts are used in commercial applications where superior strength is needed, as epoxy has higher compressive strength than concrete. In home applications, it is used on tile and stone kitchen countertops, backsplashes and in bathrooms. Modified epoxy grouts include cement; however, they are harder, form greater bond and are more stain resistant than traditional tile grouts. Epoxy grouts offer superior stain resistance.
Thanks to their relatively low expense, cement-based grouts are the workhorse of tile installations. These cost approximately $1 to $2 per pound, while epoxy grouts can cost as much as $8 per pound. The price, however, is recouped in shelf life. Powdered cement grouts will last only about one year, whereas two-part epoxy grouts can last indefinitely in an unopened, sealed state and not subjected to freezing temperatures.
Sanded cement grout and epoxy grout have one characteristic in common: neither should be used with marble or other stones that scratch easily. Cement grouts are still considered easier to apply, although second-generation epoxies have a longer pot life as they contain detergents that allow for quick cleanup beyond the 45-minute limit of the first generation. While epoxy grouts are available in a wide range of colors and are impervious to staining, they can stain some types of tiles such as unglazed quarry or limestone. Thus, all tiles should be sealed prior to application of epoxy grout.