How to regrout a shower

What you need

• Grout removal tool or oscillating multi-tool with grout blade
• Sanded grout (walls and floors) in a colour close to the original
• Grout float, bucket, sponges, microfibre cloth
• Silicone remover and neutral-cure silicone for the corners
• Safety glasses and a dust mask — grout dust is silica

Step by step

1. Test whether regrouting is the right fix

   Push firmly on a few tiles. If any move, sound hollow, or the wall flexes, stop. That is a bedding or waterproofing failure and new grout will crack again within months. Regrouting only works when the tiles are solid and the grout is simply worn, stained or crumbling.

2. Remove the old grout to at least 3mm depth

   Work the removal tool along each joint, keeping the blade centred so you do not chip the tile edges. Do the vertical joints first, then horizontal. You want a clean channel, not a skim — new grout laid over old will sit proud and pop out.

3. Vacuum and wash the joints

   Every trace of dust has to go or the new grout will not bond. Vacuum the joints, wipe with a damp sponge, then let the whole area dry completely. Rushing this step is the single most common reason DIY regrouting fails.

4. Mix and apply the grout

   Mix to a smooth peanut-butter consistency and let it slake for the time on the bag. Hold the float at 45 degrees and press the grout hard into the joints diagonally across the tiles. Work in sections of about one square metre — grout goes off faster than you expect.

5. Clean off the haze in stages

   Wait 15–20 minutes, then wipe diagonally with a barely damp sponge, rinsing constantly. Come back an hour later for the fine haze with a dry microfibre. Too much water at this stage washes cement out of the joint and leaves it weak and patchy.

6. Silicone the corners, not grout

   Every internal corner — wall to wall, wall to floor, around the bath — must be flexible silicone, never grout. These are movement joints. Grout in a corner will crack, every time. Let the grout cure fully first, then cut the old silicone out and run a fresh neutral-cure bead.

Common mistakes

• Grouting the corners instead of siliconing them
• Not removing enough of the old grout, so the new layer is too thin to hold
• Working with the joints still damp or dusty
• Using too much water when cleaning, which leaves soft, crumbly joints
• Sealing over mould — it grows straight back through