How to Re-Grout Bathroom Tile

Grout that’s stained, cracked, crumbling, or mildewed can make an otherwise good bathroom look neglected – and failed grout eventually allows water to penetrate behind tile, causing much larger and more expensive damage. Re-grouting is the right fix for deteriorated grout, and it’s well within the reach of a patient DIYer. The job requires careful removal of old grout, thorough cleaning, and precise application of the new grout – done right, the result lasts 10–15 years.

This guide covers floor tile re-grouting, which is more demanding than wall tile because the joints are more exposed and traffic-bearing. The process for wall tile is the same, but floor grout must be sealed after application to resist moisture and staining.

What You’ll Need

Tools

• Oscillating multi-tool with grout removal blade (most effective) or manual grout saw
• Shop vacuum
• Grout float (rubber-faced)
• Bucket and sponges
• Margin trowel or mixing paddle (for mixing grout)
• Grout sponge (large, fine-pore)

Materials

• Unsanded grout (for joints 1/8 inch or less) or sanded grout (for joints over 1/8 inch)
• Grout sealer (for floor tile)
• Grout cleaner or dilute bleach solution (for pre-cleaning)
• Grout color-matching chart (hardware stores have these; take a tile chip or photo)

Step 1: Select Matching Grout

To start your project, you need to identify the exact type and color of your existing grout. Begin by taking a clear, well-lit photo of your wall or floor, or carefully use a flathead screwdriver to chip out a small, pea-sized sample of the old material. You must take this sample to a home improvement store to hold it against physical color swatches; photos on your phone or computer screen will be misleading due to lighting differences. You also need to determine if your grout is sanded or unsanded. Sanded grout feels gritty to the touch and is used for wider gaps (typically larger than 1/8 inch), while unsanded grout is smooth and meant for very tight joints. Choosing the correct texture is vital for the structural integrity of your tile.

Step 2: Remove the Old Grout

Now it is time to clear away the old, crumbling grout to make room for a fresh, strong bond. The most efficient way to do this is with an oscillating multi-tool fitted with a carbide grout removal blade. Before you begin, set your tool to a low speed to maintain better control and prevent the blade from skidding across your tiles. Carefully guide the blade along the center of each grout line, keeping it perpendicular to the wall. Your goal is to remove the old material to a depth of at least two-thirds of the tile’s thickness. If you do not go deep enough, the new grout will not have enough space to anchor itself, leading to cracking later on. Once you have finished clearing the lines, use a shop vacuum with a narrow nozzle attachment to suck up all the dust and loose debris.

Step 3: Inspect the Tile After Removal

Now that you have cleared out the old grout, take a moment to closely inspect your tiles before moving forward. This step is crucial because grout acts as a decorative seal, not a structural adhesive. Gently press down on each tile, especially those near the edges or corners, to check for any “play.” If a tile wobbles, shifts, or makes a clicking sound, it has lost its bond with the wall. If you ignore this, the movement will eventually cause your new grout to crack and crumble within weeks.

To fix loose tiles, carefully pry them away from the wall, scrape off the old mortar from both the tile and the wall surface, and apply a small dab of fresh thin-set or construction adhesive specifically made for tiles. Press the tile back into place, ensuring it is flush with its neighbors. If you notice any tiles that are already cracked, it is best to replace them entirely now. Grout will not bridge a crack; the movement of the tile behind the surface will mirror itself in the new grout line immediately.

Step 4: Clean the Joints

Now that you have cleared the old grout, your tile lines need to be spotless to ensure the new material sticks properly. Start by using a vacuum with a hose attachment to suck out any loose dust or debris hiding deep in the joints. Once the area is clear, wipe the entire surface firmly with a clean, damp cloth or sponge. If you spot any stubborn dark patches or mold on the edges of the tiles, mix a cleaning solution using one part bleach to ten parts water. Gently scrub these spots, then wipe them away with plain water.

Most importantly, wait until the joints are bone-dry before moving on. This is critical because if the joints are damp, the new grout will soak up that extra moisture, which prevents it from curing correctly. This results in weak, crumbly, or discolored lines that won’t hold up over time. Aim for at least one hour of drying time – patience here is the secret to a long-lasting finish.

Step 5: Mix the Grout

Mixing grout is the most critical step for a durable finish. Start by pouring the recommended amount of water into a clean plastic bucket, then gradually add your grout powder. Always add powder to water – never the other way around – to prevent dry clumps from settling at the bottom. Use a margin trowel or a drill-mounted mixing paddle on a very low speed to blend the mixture. You are aiming for a smooth, consistent texture that looks and feels like creamy peanut butter. If the mixture is too runny, it won’t set properly; if it is too dry, it will crumble during application.

Once you reach the right consistency, stop and let the mixture “slake” (sit undisturbed) for five to ten minutes. This allows the water to fully activate the chemical additives in the grout powder. After this rest period, stir it one last time briefly. Do not add any extra water at this stage, as it will weaken the final bond.

Step 6: Apply the Grout

Now it is time to fill those gaps. Scoop a generous amount of grout onto your rubber float. Hold the float at a 45-degree angle to the wall and spread the grout diagonally across the tiles. Working diagonally is crucial; if you move parallel to the grout lines, the edge of the float will scoop the fresh material right back out of the joints. Use firm pressure to push the grout deep into the spaces until they look completely packed. Work in small sections, about 10 to 15 square feet at a time, so the grout does not dry out before you can clean it.

Once the joints are packed, hold your float nearly perpendicular – almost straight up – to the tile surface. Use this edge to squeegee off the excess grout, moving diagonally again to keep the face of your tiles clean. You want the grout to be flush with the surface of the tiles, not piled on top.

Step 7: Clean the Tile Surface

Now that your grout is in place, it is time for the final cleanup. Wait 15 to 30 minutes for the grout to set; you will know it is ready when the surface of the grout looks dull rather than wet. Using a large grout sponge, wring it out until it is barely damp. If the sponge is too wet, you will wash the grout right back out of the gaps.

Wipe the tiles using smooth, diagonal arcs across the joints. Working diagonally is crucial because moving parallel to the grout lines can accidentally scoop the fresh grout out. Rinse your sponge frequently in a bucket of clean water to keep it from becoming clogged with residue. If a thin, powdery haze remains after two or three passes, gently wipe the surface with a clean, dry microfiber cloth to buff it away. Take your time – this step is all about patience, not pressure.

Step 8: Cure and Seal

Now that your grout is in place, patience is your best tool. You must keep all foot traffic off your newly finished floor for 24 to 72 hours, depending on the specific instructions on your grout packaging. Rushing this curing process can cause the grout to crack or discolor. Once it has fully cured – ideally waiting at least 48 hours – it is time to protect your hard work with a grout sealer. This clear barrier prevents water, soap scum, and grime from soaking into the porous material, which significantly extends the life of your installation.

To seal, use a small applicator brush or the tip of your sealer bottle to carefully trace each grout line. Work in small sections, and be sure to wipe away any excess sealer that touches the surface of the tiles immediately with a clean, dry microfiber cloth. If left to dry on the tile, the sealer can become tacky or create an unsightly haze.