Grouting is the finishing step in installing a tile wall or floor. Grout serves a dual function of filling the spaces between the tiles and providing stability. It also provides an aesthetic function since using grout in different colors, textures, or tints can create totally different appearances with exactly the same tiles.
By far, the most common tile grout is made using Portland cement, although specialty grouts manufactured from materials such as epoxy are available for specialized applications. 2 main types of grout are used in homes, sanded, or unsanded. Sanded grout has a heavier texture and is used when the seams between tiles are more than 1/16-inch (about the thickness of a penny), while unsanded grout works better when the tile seams are closer together.
Grout is applied after the tiles have been laid and the mortar bed/mastic has been allowed to set for a day or so. The process is fairly straight forward, but it does require you get down on your knees. A good pair of knee pads is a necessity.
Before applying any grout, remove the spacers that were used between the tiles to position them properly. You also need to see if any mastic or mortar has been left on the surface or in the cracks between the tiles. A utility knife should be able to pop the spacers out of the seams as well as scrape any left over adhesive form the tile surfaces.
Check that all of your tiles are firmly attached. If 1 or 2 are loose, it's much easier to pick them up and apply more adhesive before you start grouting. Apply tile grout in small areas. Keep your work area small and manageable, because grout starts setting as soon as it's been mixed and if you try to cover too large an area some will have set up before you can smooth the grout seams.
You can buy premixed grout or make your own following the manufacturers directions on the package. Before you actually begin grouting, use a spray bottle to give the tiles a light misting of water. This will prevent the tiles from drawing moisture from the grout.
Apply the grout with a rubber tile float held at a 45° angle. Angling the float this way will push the grout all the way down into the cracks between the tiles. Once the grout is in the seams, use the grout float to remove any grout remaining on the surface.
Once you've installed the grout in the work area, it's time to work the grout. Working the grout involves cleaning the tile surfaces while at the same time compacting the grout in the tile seams. Use a clean, damp sponge again held diagonally to the tile seams to remove any grout left on the surface.
Pushing down firmly will compact the grout in the seams at the same time. Rinse your sponge and change the water often so the tile surfaces are being cleaned with fresh water. Finish grouting and working the grout in 1 section, before moving onto the next sections and repeating the process. Allow the grout to set overnight, then clean any remaining grout haze with an old towel or a piece of cheesecloth.