Sanded grout and non-sanded grout
Grout comes in two variants – sanded and non-sanded. But before we differentiate the two types of grout, a brief explanation on what grouts are is required.
Grout is simply the filler used for the gaps or joints between adjacent tiles. Aside from being a filler, grout also serves a protective and aesthetic function. Without grout water will seep through the tile joints, which can weaken the installation. Grout can also be applied with its own color. Hence, the tile-grout color combination can serve as a design feature.
Tiling grout is commonly a mixture of cement, water and sand, particularly in the case of sanded grout. There are also tiling grouts that are epoxy or resin based rather than being cement based.
Going back to the difference between sanded and non-sanded grouts, their dissimilarity is not just about whether they contain sand in them or not. Another key distinction is in their particular purpose. Non-sanded grout is used primarily for wall or floor tile work with joints no wider than 1/8 inch. In contrast, sanded grout is more common for floor tile work with tile joints wider than 1/8 inch. Tile work for walls that have joints wider than 1/8 inch would also require sanded grout but such cases are rare.
If you use non-sanded grout on gaps wider than 1/8 inch, the grout will crack and fail. It is therefore the width of the tile joint that dictates which of the two grout classes will be used for the job.