What grout is used for floor tile?

Most often, sanded grout is used for floor tiles because the grout lines are usually greater than 1/8" wide. Sanded grout is necessary for the wider lines to give added strength, and to keep your grout from cracking and chipping out. Unsanded grout must be used if your grout lines are narrower than 1/8", because the grains of sand in sanded grout could cause air pockets and prevent good adhesion to your tiles - and it will crack and chip out as well. Sanded and unsanded grouts are cement-based.

One alternative grout on the market is epoxy-based. It is neither sanded nor unsanded, but will work fine in either narrow or wider grout lines.

If your grout lines are wider than 1/2", or if you are using saltillo tiles, you must use saltillo grout. Other grouts will not handle this wider width.