How to Regrout Tile: Step-by-Step Without Repeating the Failure

To regrout tile, remove the old grout to at least two thirds of the joint depth (ideally full depth), vacuum the joints clean, dampen them lightly, then pack new grout firmly with a rubber float, tool the joints, and clean with a barely damp sponge. Fix whatever made the old grout fail first, or the new grout will fail the same way.

Should you regrout at all?

Regrouting is the right repair for grout that is cracked from shrinkage, eroded, stained past cleaning, crumbling in spots, or the wrong color. It is the wrong repair when tiles are loose or hollow, when water has damaged the wall or subfloor behind them, or when the cracking comes from deflection or missing movement joints. Run the diagnosis in why grout cracks and the decision checklist in repair or replace grout before you start.

A practical pre-check: tap every tile in the area with the handle of a screwdriver. Solid tiles give a sharp, high note. If more than a few tiles sound hollow, or if any tile moves when pressed, stop and plan to reset those tiles. In a shower, press firmly on the wall near the bottom rows and the valve; soft or spongy spots mean the backer is wet and the job is bigger than grout.

Choosing the replacement grout

You are not obliged to use the same type of grout that was there. Regrouting is a chance to upgrade, but the joint width and tile surface still decide what will work.

For wet areas, epoxy grout is the most stain and water resistant choice, but it is unforgiving. A first-time installer regrouting a full shower will usually get a better result with a high-performance cement grout and a penetrating sealer. Use the grout calculator to estimate quantity, then add 10 to 15 percent because old joints are often deeper and less uniform than new ones.

How deep to remove the old grout

New grout bonds to the tile edges, not to the old grout beneath it. A shallow layer has almost no edge contact, so it loosens and flakes. That is the single most common reason regrout jobs fail.

Tool selection, technique and dust control for this phase are covered in detail in how to remove grout. The short version: carbide hand saws and oscillating multi-tools with carbide or diamond blades are the safe options for most homeowners; grinders are fast but chip tile and can cut into membranes.

Step-by-step regrouting

Plan on a full day for an average tub surround or small bathroom floor, most of it spent on removal. Shower-specific details (curbs, niches, drying the wall) are in regrouting a shower. Work at room temperature: most cement grouts want 50 to 90 deg F (10 to 32 deg C) during application and cure, and epoxy is happiest in the middle of that range. Keep showers dry for at least 24 hours before starting so the joints and backer are not saturated.

1. Protect the area. Tape off tubs, fixtures and adjacent surfaces. Lay a drop cloth in the tub to catch debris and protect the finish. Remove the drain cover and plug the drain so grout chunks and sand cannot go down it.
2. Cut out the movement joints first. Slice out any caulk or grout at inside corners, the tub line, the floor-to-wall joint and around fixtures with a utility knife or carbide tool. These joints will get sealant at the end, not grout.
3. Remove the old grout. Remove to at least two thirds of the joint depth, keeping the tool centered so you do not chip the tile edges. Work in a consistent direction and check depth with a nail or a depth probe as you go.
4. Scrape the tile edges. Run a carbide scribe or a stiff putty knife along both tile edges in every joint. Old grout and haze left on the edges is what new grout has to bond to, so clean edges matter more than a perfectly uniform floor in the joint.
5. Vacuum and wipe. Vacuum all joints with a crevice tool, then wipe the tile with a damp microfiber cloth. Any dust left in the joint acts as a bond breaker. If soap scum or mineral film covers the tile, clean it now with a suitable cleaner and rinse well.
6. Dampen the joints. For cement grout, mist or sponge the joints just before grouting so the old material and tile edges do not suck water out of the new grout. The joints should look darker but have no standing water. Skip this for epoxy and most urethane grouts, which need dry joints; follow the TDS.
7. Mix the grout. Mix to the low end of the water range on the bag, let it slake (rest) for the time the TDS gives, typically 5 to 10 minutes, then remix briefly without adding water. Mix only what you can place and clean in about 20 to 30 minutes.
8. Pack the joints. Hold a rubber grout float at about 45 degrees and force grout diagonally across the joints, working each area twice in different diagonal directions. Old joints are often irregular, so press hard and look for voids. Then hold the float nearly upright (about 90 degrees) and drag it diagonally to remove excess.
9. Tool and shape the joints. When the grout firms slightly, run a rounded jointer or the end of a toothbrush handle along the joints to compress them and give a consistent profile slightly below the tile surface. Consistent depth is what makes regrouted joints look uniform.
10. Clean the surface. When the grout is firm to the touch (often 15 to 30 minutes for cement grout), wipe diagonally with a well-wrung sponge, rinsing often in a bucket of clean water. Change the water frequently. Too much water at this stage washes out cement and pigment and causes light, blotchy joints.
11. Remove haze. After the grout has set, typically 1 to 3 hours depending on product, buff remaining film with a dry microfiber cloth. Stubborn residue can be removed after cure as described in how to remove grout haze.
12. Seal the movement joints. After the grout has cured enough to resist abrasion (follow the grout TDS, often 24 hours), fill the corners, tub line and perimeter joints with a color-matched sealant suitable for the location, such as 100 percent silicone in showers.
13. Cure and protect. Keep foot traffic off floors for at least 24 hours and showers dry for the period the grout maker specifies, commonly 72 hours for cement grout. Avoid fans and heaters blowing directly on the grout, which dry it unevenly.
14. Seal the grout if required. Cement grout usually benefits from a penetrating sealer once fully dry, commonly 48 to 72 hours for polymer-modified grout and longer for standard grout; read the label. Epoxy grout does not need sealing. See how to seal grout.

Partial regrouting and color matching

Spot regrouting a few cracked joints is tempting, but matching old grout color is difficult. Old cement grout has aged, absorbed cleaners and sealer, and its pigment has shifted. Even the same product and color from a new bag usually looks different next to grout that has been in service for years. Expect a visible patch; techniques for getting close are in matching existing grout color.

Ways to manage it:

• Regrout to natural boundaries. Do a full wall, a full floor area to a threshold, or the whole backsplash, so any color shift reads as intentional.
• Test first. Grout a scrap of tile or a hidden joint, let it dry fully for several days, and compare in the room's light. Cement grout dries much lighter than it looks wet.
• Unify afterward. A grout colorant applied over both old and new grout produces one consistent color, at the cost of a coating that needs maintenance.
• Use a color-consistent grout. High-performance and premixed grouts generally dry more uniformly than standard cement grout, which helps on large regrouts.

Regrouting mistakes that cause early failure

• Shallow removal. The thin layer of new grout cracks and pops out within months. See grouting over old grout for why.
• Dusty joints. Fine dust left after removal prevents bond. Vacuum, then wipe.
• Soaking the joints. Standing water dilutes the grout at the bottom of the joint and causes dark or light patches. See grout discoloration and shading.
• Grouting wet showers. Moisture trapped in the wall slows cure and can bring efflorescence to the surface.
• Regrouting over movement. If the original failure came from deflection or missing expansion joints, regrouting buys time and nothing more.
• Retempering. Adding water to stiffening grout weakens it. Discard it and mix a fresh batch.