In most cases, unsanded grout is appropriate for applications that require a grout width of less than 1/8 inch, while sanded grout is used for wider grout lines. Sanded grout contains tiny particles of sand that prevent the mixture from shrinking as it cures.
Most tile applications, such as floors and countertops, require sanded grout, especially when using ceramic tile. However, unsanded grout is easier to apply on vertical walls such as backsplashes and bathtub surrounds. It adheres to the cracks between tiles and does not slip off the surface like sanded grout does.
Although it is possible to use unsanded grout in narrow joints, it is more difficult to apply. The sand and silica mixture resists compaction between tiles, which can lead to pinhole cracks and other surface irregularities.
However, experts recommend steering clear of sanded grout for stone, granite, quartz and other smooth stone tiles. This is because the sand particles in sanded grout can scratch the surface of the stone, leaving permanent blemishes. Since non-sanded grout is smoother, it does not pose the same risks.
Epoxy grout and caulk are two alternatives to sanded and unsanded grout. Epoxy is a common substitute in applications where the owner wants to avoided staining, cracking and peeling grout, while caulk is often used for joints between walls and floors.