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.