Grout is a cement-like substance placed between ceramic, glass, or stone tiles to set and support them. There are three major types of grout:
- Portland cement based grout This is the most common type of grout, consisting of a mixture of cement and sand. It is easy to use and can be found in most home improvement stores. It was patented by Joseph Aspdin in England in 1824 and was called “Portland cement” because its color was similar to stones found in the Isle of Portland. Portland grout is available in a variety of colors.
- Epoxy-based grout This grout is much more difficult to use than Portland cement and can generally only be found in specialized tile stores. It consists of epoxy, hardeners, and sand and tends to be stronger than Portland grout and more resistant to staining, water, and etching from acids. It also is more expensive and is not recommended for the beginner because it is rather difficult to apply properly.
- Furan resin grout This grout is the most difficult to use and hardest to find of the three grouts. It contains furfuryl alcohol instead of water, making it very resistant to chemicals. Installation generally involves coating the tiles with wax and removing excess grout by steam cleaning. The grout is typically used only by professional builders.
The three basic types of grout are further divided into two subgroups: sanded or non-sanded. Sanded grout contains sand and is generally used when the tiles are 1/8 inch (4 mm) apart or larger. The addition of sand helps prevent the grout from shrinking and cracking in these larger joints. However, the sand is abrasive and delicate tiles, such as glass or marble, should be taped before grouting to prevent scratching. Non-sanded grout does not contain sand and is used in smaller joints that do not run the risk of cracking the grout.
(This section covers installation of Portland grout only, since it is the most common and easiest to apply)
Portland grout can generally be found in two forms, a cheaper, dry powder that needs to be mixed with water, and a more expensive wet grout that is ready to be applied. If using the dry powder, wear a face mask to prevent inhalation. Place some of the powder in a disposable small bucket and add enough water to make a peanut butter-like consistency. Many installers recommend using purified water instead of tap, as the minerals in tap water may cause "efflorescence", or white mineral deposits on the grout that can be difficult to remove. Stir the mixture gently, since vigorously mixing the grout may weaken it by adding air bubbles.
Professional installers use a flat piece of rubber or metal called a "grout float" to apply the grout. Here a decent amount of grout is placed on the tiles and the float is used to press the grout into the joints. I have had a great deal of success simply applying the grout with my fingers. To do this, put on some gloves and use your fingers to push the grout deeply into the gaps between the tiles, filling all areas.
Once you are finished applying the grout, wait about 30 minutes for the grout to begin to dry. Then start removing excess grout with clean, barely damp rags or sponges. Very wet sponges can inadvertently add more water to the grout and weaken it. Make sure to remove all excess grout in between and on top of the tiles. Once the grout has fully cured it will be very difficult to remove it. Any remaining residue of grout can be removed with a damp sponge followed by buffing with a dry cloth. When all excess grout has been removed the grout should be protected by sealing it with a grout sealant available at most home improvement stores.
The most important thing to remember when grouting is to not pour the wet grout down any drain in your home. The grout will most likely set in the pipes and permanently seal them. Instead, let the excess grout dry in the bucket and toss the whole thing in the garbage.
Stains in sealed grout can often be removed easily with soap or another household cleaner and a sponge. A number of commercial grout cleaning solutions are available but some people recommend trying vinegar or a baking powder solution. Bleach pens may be useful at removing tough stains in white grout. Stains that appear impossible to remove can be fixed two ways, both of which require quite a bit of work. First, you can use a tool called a “grout saw” to gently remove the top layer of grout on all the tiles and then regrout. Second, tile stores sell special grout stains that permanently color the grout and hide the stains.