Your shower tiles still look fine, but the grout between them is cracked, crumbling or stained dark in a way no amount of scrubbing will fix. Maybe a few lines have gone missing entirely near the floor, and you are starting to worry about water getting behind the wall.
Regrouting is one of the most satisfying bathroom repairs you can do yourself. This guide covers when regrouting makes sense, how to remove the old grout without chipping tile, how to choose between sanded, unsanded and epoxy grout, and how to mix, apply, cure and seal it so the job lasts.
Quick answer: Remove at least two-thirds of the old grout depth with a grout saw or an oscillating tool, vacuum and clean the joints, and let them dry. Mix new grout to the bag’s instructions, press it into the joints diagonally with a rubber float, and sponge off the haze once it firms up. Keep the shower dry for the cure time on the bag, usually 48 to 72 hours for cement grout, then seal cement-based grout once it has cured.
Should you regrout or do something else?
Regrouting makes sense when the tiles are solid and well bonded but the grout is cracked, crumbling, missing or permanently stained. Before you commit a weekend, press on the tiles near the damaged grout and tap them with a screwdriver handle.
- Tiles feel solid and sound crisp: regrouting is a good fix.
- Grout is just dirty or mildewed: try a deep clean first. Our guide on how to clean grout may save you the work.
- Only the corners or the tub joint are failing: those should be caulked, not grouted. See how to recaulk a bathtub.
- Tiles are loose, hollow sounding, or the wall feels soft: water has likely reached the backer board. Regrouting will not fix that, and you should call a pro.
Keep in mind that grout is not waterproof. It is porous by nature, and the real water barrier sits behind the tile. New grout keeps water out of the joints and looks great, but it cannot repair a failed waterproofing layer.
Choosing the right grout
The width of your grout joints and the type of tile decide which grout to use. According to This Old House, sanded grout suits joints wider than 1/8 inch, while unsanded grout is for joints narrower than 1/8 inch. Sanded grout can scratch polished marble and glass tile, so use unsanded or epoxy on those surfaces.
| Grout type | Best for | Pros | Cons |
|---|---|---|---|
| Sanded cement grout | Joints wider than 1/8 inch, most ceramic and porcelain | Strong, affordable, resists shrinking in wide joints | Needs sealing, can scratch glass and polished stone |
| Unsanded cement grout | Joints narrower than 1/8 inch, glass and polished stone | Smooth, easy to push into thin joints | Can shrink or crack in wide joints, needs sealing |
| Epoxy grout | Showers where stains and mildew are a constant fight | Very stain and water resistant, no sealing needed | Short working time, harder to clean up, costs more |
| Premixed urethane or polymer grout | Small repairs and beginners | Ready to use, many need no sealing | Costs more per joint, follow cure times closely |
Match the new grout to any old grout you are keeping, or plan to regrout the whole wall so the color is consistent. Grout often dries lighter than it looks wet, so check the color on the manufacturer’s chart rather than the wet sample.
Tools and materials
- Manual grout saw or carbide grout rake, and an oscillating multi-tool with a grout blade for long runs
- Utility knife for removing old caulk
- Shop vacuum and a stiff nylon brush
- Painter’s tape to protect tub edges and fixtures
- Grout (enough for your joint size), clean water or the additive the bag allows
- Bucket, margin trowel and a drill with a slow mixing paddle for larger batches
- Rubber grout float
- Two large grout sponges, a bucket of clean water and microfiber cloths
- Penetrating grout sealer and a small applicator brush or bottle
- Safety glasses, a respirator rated for dust (N95 or better), and gloves
Safety note: Cement grout contains sand and Portland cement, and grinding it out creates fine dust you should not breathe. Wear a well-fitted respirator and eye protection, run the bathroom fan, and vacuum as you go instead of sweeping. Cement grout is also alkaline, so wear gloves while mixing and applying it.
Step 1: Remove the old grout
This is the slowest part of the job and the one that decides how long the new grout lasts. New grout needs enough depth to lock in. Aim to remove at least two-thirds of the old grout depth, and keep the depth even along each line.
- Cut out any caulk at the corners, along the tub and around fixtures with a utility knife.
- Score down the center of each joint with a grout saw or rake to create a guide groove.
- Work outward toward each tile edge with short, controlled strokes. Let the tool do the work.
- For long runs, switch to an oscillating tool with a carbide or diamond grout blade on low to medium speed. Keep the blade centered and do not tilt it into the tile edges.
- Vacuum often so you can see your progress.
Grout saw or oscillating tool?
A manual grout saw is cheap, quiet and very controllable, which makes it ideal around fixtures, in corners and for small areas. An oscillating tool is far faster on a full shower but takes a steady hand, since one slip can chip a glazed edge. Many people use the power tool for straight runs and finish by hand.
Step 2: Clean and dry the joints
New grout will not bond well to dust, soap scum or mildew. Vacuum every joint, then scrub the tiles and joints with a mild tile cleaner or dish soap solution and rinse well. If you see mildew, treat it before regrouting; our guide on getting rid of bathroom mold explains how.
Let everything dry thoroughly, ideally overnight with the fan running. Just before grouting, wipe the joints with a barely damp sponge. A slightly damp joint stops dry backing from pulling water out of the fresh grout too fast, but there should be no standing water. Tape off the tub edge, drain and valve trim.
Step 3: Mix the grout
Read the bag before you start. Mixing ratios, working time and cure times differ between brands, and the manufacturer’s numbers always take priority.
- Pour most of the measured water into a clean bucket first, then add powder gradually.
- Mix by hand or with a paddle on a slow drill until smooth, with a texture similar to peanut butter. Fast mixing whips in air bubbles.
- Let cement grout rest for the slake time on the bag, then remix briefly without adding more water.
- Mix only as much as you can use in about 20 to 30 minutes. With epoxy, mix even smaller batches because it sets faster.
Avoid adding extra water to stiffening grout. It weakens the grout and causes uneven, blotchy color.
Step 4: Apply the grout
- Work in small sections of a few square feet at a time, starting at the top of the wall.
- Load the float and hold it at about a 45-degree angle. Push grout diagonally across the joints, pressing firmly so it fills each joint completely.
- Make a second pass in the other diagonal direction to fill any gaps.
- Turn the float almost on edge and drag it diagonally across the tiles to scrape off the excess.
- Leave the inside corners, the joint where the wall meets the tub or pan, and joints around fixtures empty for caulk.
Step 5: Clean off the haze
Timing matters here. Wait until the grout firms up, typically 15 to 30 minutes depending on the product and room temperature. Press a fingertip lightly on a joint: if it feels firm and does not come away on your finger, it is ready.
- Wring the sponge until it is barely damp.
- Wipe diagonally across the joints in light passes, rinsing and wringing the sponge often.
- Use the rounded edge of the sponge to smooth and shape the joints to an even depth.
- After the surface dries, buff the remaining film off the tiles with a dry microfiber cloth.
A wet sponge or heavy pressure pulls grout out of the joints and leaves them weak and patchy. For epoxy, follow the manufacturer’s cleanup method closely, since dried epoxy haze is very hard to remove.
Step 6: Cure, caulk and seal
Cure times vary by product, so always follow the bag. These ranges are typical and help you plan:
| Grout type | Keep the shower dry for | Seal after |
|---|---|---|
| Cement-based (sanded or unsanded) | 48 to 72 hours | At least 48 hours, longer if the bag says so |
| Polymer-modified cement | 24 to 48 hours | Per bag, if sealing is recommended |
| Epoxy | About 24 hours | Not needed |
| Premixed urethane | Per bag | Usually not needed |
Steam counts as water, so do not run a hot shower in the room next door with the door open. Once the grout has cured, caulk the inside corners and the tub or pan joint with 100% silicone or a kitchen and bath sealant in a matching color.
To seal cement grout, apply a penetrating sealer to the grout lines only, let it soak in for the time on the label, and wipe any excess off the tile before it dries. Let the sealer cure before using the shower. Test it later by dripping water on a joint: if the water beads, the seal is working, and if the grout darkens quickly, it is time to reseal.
Common mistakes to avoid
- Grouting over old grout. A thin skin of new grout on top of old grout cracks and pops out within months.
- Grouting the corners. Inside corners and changes of plane move slightly and crack. Use flexible caulk there.
- Using sanded grout on glass or polished stone. It can leave permanent scratches.
- Retempering with water. Adding water to stiffening grout weakens it.
- Using the shower too soon. Early water exposure can wash out pigment and soften joints.
When to call a pro
Call a tile contractor if you notice any of these red flags:
- Tiles that are loose, cracked, hollow sounding or move when pressed.
- A soft or crumbling wall behind the tile, or water stains on the ceiling below or the wall on the other side.
- Mold that returns behind the grout or under tiles after cleaning.
- Natural stone or glass tile you are not comfortable working on.
According to HomeAdvisor’s regrouting cost guide, professional shower regrouting typically costs $600 to $2,500, with many projects around $1,500, or roughly $10 to $25 per square foot including materials and labor. This Old House estimates DIY materials and tools at about $100 to $200 and professional sealing at about $2 to $5 per square foot.
| Option | Typical cost |
|---|---|
| DIY materials and tools | $100 to $200 |
| Professional regrouting, per square foot | $10 to $25 |
| Professional regrouting, whole shower | $600 to $2,500 |
| Professional grout sealing, per square foot | $2 to $5 |
If tiles are loose or damaged, a retile may be the better investment, and replacing a single cracked tile is often doable; see how to replace a cracked tile.
Frequently asked questions
Can you put new grout over old grout?
Not successfully. A thin layer of new grout has nothing to grip and soon cracks and flakes off. Remove at least two-thirds of the old grout depth so the new grout can fill and lock into the joint.
How long does it take to regrout a shower?
Plan on a full weekend for a standard shower if you are new to it, plus the cure time before showering. Grout removal usually takes the longest.
How long after grouting can I shower?
For most cement grouts, wait 48 to 72 hours, and longer if the bag says so. Epoxy grout is often ready in about 24 hours. Check your product’s label, since cure times vary by brand and temperature.
Should I use sanded or unsanded grout in a shower?
It depends on the joint width. Use sanded grout for joints wider than 1/8 inch and unsanded for narrower joints, or on glass and polished stone that sand could scratch.
Do I need to seal new grout?
Cement-based grout should be sealed once it cures to slow water and stain absorption. Epoxy and many premixed urethane grouts do not need sealing.
The bottom line
A successful regrout comes down to removing enough old grout, choosing the right type for your joint width, mixing it carefully and giving it time to cure before water and sealer. Caulk the corners instead of grouting them, and if tiles are loose or the wall is soft, stop and call a pro, because the problem is behind the tile.
