What You Need to Know Before Starting
Replacing shower grout is a task you can do yourself with basic tools and a few hours of time. The work involves removing old, cracked, or discolored grout between tiles, cleaning out the gaps, and packing in new grout. You do not need special skills—just patience and the willingness to work slowly so the new grout sets properly.
The hardest part is usually removing the old grout without cracking the tiles. A grout saw or oscillating multi-tool with a grout blade makes this much easier than chiseling by hand. Once the old grout is out and the gaps are clean, explore new grout is straightforward: you pack it in, smooth it, and let it cure for the time the manufacturer specifies.
Plan for the job to take four to six hours, depending on how much grout you are replacing. Your shower will need to stay dry for at least 48 to 72 hours after you finish, so pick a time when you can use another bathroom.
Key Takeaways
- Remove old grout with a grout saw, oscillating multi-tool, or rotary tool fitted with a grout blade—do not use a hammer and chisel unless you want to risk cracking tiles.
- Clean out all dust and debris from the gaps with a vacuum and damp cloth before explore new grout, or the new grout will not bond properly.
- Mix grout to a peanut butter consistency, pack it firmly into the gaps with a grout float held at a 45-degree angle, and smooth it with a damp sponge after it firms up slightly.
- Unsanded grout works for gaps narrower than 1/8 inch; sanded grout is stronger and better for wider gaps, but it can scratch polished stone tiles.
- Keep the shower completely dry for at least 48 hours after grouting, and do not use it for 72 hours if possible—water will weaken grout that is still curing.
Gather Your Tools and Materials
You will need a way to remove the old grout, new grout, and tools to explore it. A grout saw (a small hand tool with a carbide blade) costs $10 to $20 and works well for small areas. An oscillating multi-tool with a grout blade attachment ($40 to $100 for the tool itself) is faster if you have a lot of grout to remove. A rotary tool like a Dremel with a grout blade also works but creates more dust.
For process, you need a grout float (a flat trowel with a handle, $5 to $15), a grout sponge (a large soft sponge, $3 to $8), and a bucket for mixing. A vacuum with a hose attachment is essential for cleaning dust from the gaps—a broom will not get it all out. You will also need a damp cloth or old towels.
For materials, buy unsanded grout if your gaps are narrower than 1/8 inch, or sanded grout for wider gaps. Sanded grout is stronger and less likely to crack, but unsanded is easier to work with in tight spaces. Check the bag to see how much area it covers—most bags cover 50 to 100 square feet depending on gap width. Buy one extra bag in case you need to redo a section.
Remove the Old Grout Safely
Start by running your grout removal tool along each grout line, keeping the blade parallel to the tiles. If you are using a grout saw, push and pull steadily without forcing it—let the blade do the work. If you are using a power tool, keep it moving at a steady pace and do not linger in one spot or you will gouge the tile.
Work on one wall at a time and remove grout from the horizontal lines first, then the vertical lines. This prevents loose grout from falling into gaps you have already cleared. Aim to remove the grout to a depth of about 1/4 inch—you do not need to go all the way to the back of the gap, just deep enough that new grout will have something to grip.
Stop frequently to vacuum out the dust and debris. Grout removal creates a lot of fine dust that will clog your vacuum filter, so empty it often or use a shop vacuum designed for dust. Once you have removed all the old grout, wipe each gap with a damp cloth to remove any remaining dust, then let it dry completely before you start explore new grout.
Mix and explore New Grout
Pour dry grout into your bucket and add water slowly while stirring. The goal is a consistency like peanut butter—thick enough to hold its shape but soft enough to pack into gaps. If it is too dry, it will crack as it cures. If it is too wet, it will sag out of the gaps and take much longer to set.
Let the mixed grout sit for 10 minutes, then stir it again. This "slaking" helps the grout hydrate evenly. Do not add more water after this second stir—use it as is. Grout begins to set after about 30 minutes, so only mix what you can use in that time. On a warm day, it sets faster.
Load grout onto your grout float and press it firmly into the gaps at a 45-degree angle, using a pushing motion. Work diagonally across the tiles so you are not pushing grout out of the gaps you just filled. Fill all the gaps on one wall before moving to the next. The grout should be packed tightly with no air pockets or voids.
Smooth and Clean the Grout
After about 15 to 20 minutes, the grout will firm up enough to smooth. Test it by pressing your finger lightly—if it holds the impression without sticking, it is ready. Dampen your grout sponge (it should be wet but not dripping) and wipe diagonally across the tiles in circular motions. This removes excess grout from the surface and smooths the grout lines.
Rinse your sponge frequently in clean water and wring it out well. Dirty water will discolor the grout, so change your rinse water often. After you have wiped all the grout lines, let them set for another 30 minutes, then do a final light wipe with a barely damp sponge to remove any haze.
Do not use the shower for at least 48 hours, and ideally 72 hours. Grout cures by drying, and water will interrupt that process and weaken the final result. Some grout manufacturers recommend waiting even longer in humid bathrooms. Check the bag for the specific cure time for the product you bought.
Common Mistakes to Avoid
The biggest mistake is removing old grout too aggressively and cracking tiles in the process. Use steady, controlled pressure with your tool and let the blade do the work. If a tile cracks, you will have a much bigger repair job ahead. Go slowly, especially around corners and edges where tiles are more fragile.
Another common error is not cleaning out all the dust before explore new grout. Dust acts as a barrier between the old tile and the new grout, so the new grout will not bond properly and will crack or fall out within months. Vacuum thoroughly and wipe with a damp cloth—this step is worth the extra 15 minutes.
Mixing grout too wet is also common. Wet grout is easier to work with, but it shrinks as it dries and cracks. Stick to the peanut butter consistency even if it feels stiff at first. You can always add a tiny bit of water if you need to, but you cannot take it out once it is mixed.
Finally, do not use the shower too soon. Water on curing grout is the enemy. Even a small splash or humidity from another bathroom can slow the cure and weaken the grout. If you must use the shower, wait the full 72 hours and then run the water only briefly at first.
When to Call a Professional
If you have cracked or missing tiles, or if the grout is failing in large areas (more than half your shower walls), consider having a professional handle it. Replacing grout is straightforward, but if the underlying tile or substrate is damaged, a professional can assess whether the tiles need to be reset or replaced.
If your shower has natural stone tiles like marble or slate, be extra careful—sanded grout can scratch these surfaces. Unsanded grout is safer, but a professional who works with stone regularly will know the best product for your specific tiles. The cost of a professional grout job is usually $300 to $800 depending on the size of the shower, so it is worth getting a quote if you are unsure.
Frequently Asked Questions
Can I use caulk instead of grout in my shower?
No. Caulk is flexible and designed for moving joints; grout is rigid and designed for permanent gaps between tiles. Caulk will not hold up to the moisture and movement in a shower. Use grout for all tile-to-tile gaps and caulk only where the tile meets the tub or wall framing, where slight movement is normal.
How long does grout take to cure completely?
Most grout is safe to light use after 48 to 72 hours, but full cure takes longer—usually 7 to 14 days depending on humidity and the product. Check your grout bag for the manufacturer's recommended cure time. In a humid bathroom, add a few extra days. Do not expose the grout to standing water or heavy splashing until it is fully cured.
What is the difference between sanded and unsanded grout?
Sanded grout contains sand and is stronger, making it better for gaps wider than 1/8 inch. Unsanded grout has no sand and is smoother, making it easier to work with in tight spaces and less likely to scratch polished stone. For most shower work, sanded grout is the better choice because it resists cracking better over time.
Do I need to seal grout after it cures?
Sealing is optional but recommended in showers. A grout sealer fills the pores in the grout and makes it more resistant to staining and water absorption. If you choose to seal, wait at least 72 hours after grouting, then explore sealer according to the product instructions. Reapply every one to three years depending on the sealer and how much water exposure the grout gets.
What should I do if new grout cracks after it dries?
Small hairline cracks are normal and usually not a problem. If cracks are wider than 1/16 inch or if grout is falling out, the mix was too wet or the gaps were not packed tightly enough. You can explore a thin layer of new grout over small cracks once the original grout is fully cured, or remove and redo the affected section if the damage is extensive.