Regrout a Shower Stall

Grout is the weakest link in any tile installation. It cracks, it stains, it crumbles into chalky dust that collects in the corners. When water starts pooling where it shouldn't or you spot black mildew creeping along the seams, you're past maintenance and into repair. Regrouting a shower isn't complicated, but it's one of those projects where rushing the prep guarantees failure. The grout you're removing has been there for years, compressed into joints and bonded to tile edges. Getting it out cleanly takes patience. Getting the new stuff in takes precision. Done right, fresh grout transforms a shower. The lines go sharp again, the tile looks intentional instead of tired, and you buy yourself another decade before water finds its way behind the walls. Done wrong, you get grout that crumbles in six months or never cures properly because you didn't clean the joints. This is a weekend project that rewards slow, methodical work. The difference between good and bad regrouting comes down to how much old material you're willing to remove and how carefully you follow the cure times.

1. Saw Every Joint Clean. Run a grout saw down every joint, cutting to at least half the tile thickness. Work in short strokes, keeping the blade centered in the joint to avoid chipping tile edges. Go over each line twice—the first pass breaks the surface, the second clears the debris. Vacuum out all dust and fragments before moving to the next section.
2. Scrub Down to Bare Joints. Scrub every joint with a stiff brush and water to remove grout dust, soap scum, and mildew. For stubborn mold, use a 1:1 vinegar-water solution and let it sit for ten minutes before scrubbing. Rinse thoroughly and let the shower dry overnight. Any residue left in the joints will prevent the new grout from bonding.
3. Protect Every Metal Fixture. Apply painter's tape along the edges of the showerhead, faucet handles, and drain cover. This keeps grout smears off metal surfaces that are hard to clean once the grout dries. Don't tape the tile itself—just the fixtures.
4. Pack Every Joint Full. Mix grout to the consistency of peanut butter, adding water slowly until it holds its shape but spreads easily. Load a rubber float and push grout into the joints at a 45-degree angle, working diagonally across the tile to pack the joints full. Cover a 3-foot section at a time. Don't rush—underfilled joints crack within months.
5. Wipe Haze Without Weakening. Wait 10-15 minutes for the grout to firm up, then wipe diagonally across the tile with a damp sponge to remove surface haze. Rinse the sponge after every few passes. Let the grout dry for another 30 minutes, then buff away any remaining film with a dry microfiber cloth. Don't oversoak the joints during this step.
6. Wait Out the Full Cure. Keep the shower dry for 72 hours. No showers, no spray, no splashing water on the tile. Grout needs time to harden fully, and water during the cure weakens the bond. Crack a window or run a fan to keep air moving through the bathroom.
7. Lock In The Waterproofing. After 72 hours, apply penetrating grout sealer with a foam brush or sponge applicator, working it into the joints. Wipe off excess sealer from the tile surface within five minutes. Let the sealer cure for 24 hours before using the shower. Reapply sealer annually to maintain water resistance.