The last step in any DIY floor or wall tile project is called grouting — applying a thick paste that fills and seals the spaces, called grout joints, between the tiles. Standard tile grout is cement-based, or "cementitious," and comes in powder form that you mix with water. Thankfully, there are only two choices when it comes to cementitious grout for your home improvement project: sanded or unsanded.
If you are working with floor tiles, most installers and experts recommend using sanded grout thanks to its strength and durability over unsanded grout. The sanded variety shrinks less and doesn't crack as easily under pressure due to the aggregated material within the mixture. For wall tiles, unsanded grout may be a better choice, particularly if the space between the tiles is less than 1/8 inch. Unsanded grout is also typically easier to work with and is less likely to damage glass or glazed ceramic tiles during the grouting process since the mix doesn't contain harsh abrasives.
The key to successfully grouting your DIY tiling project is to work in manageable areas. For small tile jobs, you may be able to complete each stage of the grouting process over the entire area before moving on to the next stage. For larger jobs, it might be best to complete all of the grouting stages in a small area (such as 10 square feet) before starting over with a new area.
Choosing a Grout Color
Standard powdered grout is sold in a variety of colors to match or complement the tile. The best way to choose a grout color is to use a grout manufacturer's sample board that displays actual grout samples in all of the available colors. Hold one of your tiles next to each grout sample so you can see how the tile looks with the grout.
While there are grout additives that can add color to a grout mix for custom coloring, this is not recommended for beginners. It is very difficult to blend the colorant perfectly and to ensure consistent coloring from batch to batch. Any variation will be permanently visible in the tile installation. Do not attempt to color grout mix with paint or other additives not designed for tile applications.
Specialty Tools for Grouting
Grouting tile is made much easier with a few inexpensive specialty tools. The most important are a grout float and grout sponge. A grout float is similar to a trowel but has a rubbery base. You use it to apply the grout to the tile surface, push the grout into the grout joints and scrape the excess grout from the tile faces. Any standard grout float for cement-based grout is suitable.
Grout sponges are large, dense sponges with rounded edges. They are essential for cleaning excess grout from the tile faces without pulling grout from the joints. Grout sponges also are used to smooth grout joints after the grout has begun to set. Do not use standard square-edged sponges for grouting. They won't do this job effectively, and their sharp edges can mar the grout in the joints.
A couple more specialty tools are helpful but not essential. A small plastic bucket is ideal for mixing grout, and a margin trowel makes it easy to mix the grout and eliminate lumps and pockets of dry powder. For the sponging stages, you can use a small bucket to hold your rinse water, but a medium-size bucket is more convenient.
How to Grout Tile
Step 1: Protect All Surfaces
Depending on the scale of your project, use plastic sheeting or protective, nonslip paper like red rosin to protect all surfaces from grout spills or drips and secure with painters' tape.
Step 2: Prep the Surface
With needle-nose pliers, remove all tile spacers. Inspect and clean leftover adhesive and check for any loose materials between the tiles and on their faces.
Step 3: Mix the Grout
To mix grout for your DIY tile project, cut open the bag of powder and pour about half of the bag into a bucket. You'll want to follow the manufacturer's instructions for how much water to add to the mix, but it's a good idea to start with slightly less than recommended since factors like humidity can affect the ratios needed to create the perfect consistency.
With a margin trowel or other stirring tool, mix the powder and water by hand until all the lumps are eliminated, and it's the consistency of either creamy peanut butter or a thick cake batter. Slowly add more water if the mixture is too clumpy or dry. Remember to turn the bucket on an angle so all the dry mix gets incorporated.
Step 4: Slake the Grout
Once the grout reaches the proper consistency, let the grout rest or "slake" for 10 minutes. This allows the water and chemicals to activate fully and bond, otherwise the grout may crack or chip. The grout may be slightly thicker after 10 minutes, but resist the urge to add more water. Stir the grout again with the grout knife before beginning your home improvement project.
Step 5: Apply the Grout
When grouting tile, add grout to one end of the rubber grout float. Hold it at a 45-degree angle and apply it diagonally across the tiles, moving across the grout joints (the space between the tiles) until the grout has filled the spaces and is flush with the tile surface. If you are grouting wall tiles, move the float upward in a diagonal direction to reduce grout dropping on the floor.
Step 6: Remove Excess Grout
Remove excess grout from the surface of the tile with the float by turning it perpendicular to the tile. Scrape sideways in an "S" pattern while maintaining the 90-degree angle, squeegeeing as much excess grout from the surface of the tiles as possible.
Step 7: Continue Grouting the Joints
Continue to reload the float and apply grout until the section is completed. Occasionally rinse the float in warm, clean water or scrape it with a putty knife to prevent grout buildup. Let the section dry for 20 minutes.
Step 8: Clean Tiles With a Grout Sponge
Take the grout sponge, dip it in clean, hot water and wring it out so it's damp but not wet. Wipe across the tile section in a diagonal direction. Flip the damp sponge to the clean side and wipe another section, removing excess grout. Rinse the sponge and repeat until the grouted section of tiles is mostly clean. Don't worry if a haze from the grout remains — this will be removed later.
Step 9: Tool the Grout Lines
Smooth and level the grout lines with a clean sponge or a gloved finger. This is called "tooling," and the goal is consistent-looking grout joints by reducing grout lines that may be too high or uneven.
Step 10: Clean the Grout Haze
Wait an hour to let the grout set. Clean the surface of the tile with a clean, damp cloth and wipe off the remaining grout haze from the tiles. Clean the cloth frequently with warm water. Once the grout has completely hardened, use a cheesecloth or Magic Eraser to buff the tile in a circular motion.
Step 11: Clean Up Your Tools
Make sure to clean all grout tools (trowel, grout float, sponge and buckets) by rinsing them in clean water. Save any leftover dry mix in a sealable plastic bag. Label it and store it in a cool, dry place for touchups and to repair grout that may crack or chip in the future.
Step 12: Cure and Seal the Grout
Follow the manufacturer's instructions for how long the grout should cure to fully harden, but expect it to be ready to seal in 48 to 72 hours. Using a sealer on the grout will protect it from cracking and absorbing stains in the future.