How do I regrout tiles?

Grout fails because it is rigid and the joints move slightly. Regrouting the flat areas and using flexible sealant at every corner and junction is what makes the repair last rather than cracking again within months.

What you'll need

• Grout rake or oscillating tool
• Grout
• Grout float
• Sponge
• Silicone sealant (optional)
• Eye protection (optional)

Step by step

1. Rake out the old grout to at least 3mm.A manual grout rake or an oscillating multi-tool with a grout blade. New grout over old is too thin to hold and falls out within months.
2. Wear eye protection.Grout removal throws hard fragments. This is not optional with a power tool.
3. Vacuum and clean the joints thoroughly.Dust prevents adhesion. Vacuum, then wipe the tiles and let them dry completely.
4. Mix grout to a thick paste and only what you can use.It starts setting within about twenty minutes. Mix in small batches rather than one large one.
5. Work it in diagonally across the joints with a float.Diagonal strokes push grout into the joints rather than dragging it out. Press firmly to fill them completely.
6. Wipe off the excess with a damp sponge after 15-20 minutes.Rinse the sponge constantly and use light pressure. Too early and you pull grout out; too late and it sets on the tiles.
7. Polish off the haze once dry.A dry cloth after a couple of hours removes the cloudy film. Left too long it becomes difficult to shift.
8. Use silicone sealant, not grout, at every corner and junction.Wall to wall, wall to floor, tile to bath or worktop. These joints move and rigid grout cracks. This is where most regrouting fails.

Tips

• Seal the grout once fully cured, particularly in a shower. It resists staining and mould considerably better.
• Match the grout colour to the existing if you are only doing part of a wall. Colours vary and a patch is obvious.
• If grout is only discoloured rather than failing, a grout cleaner or a grout pen may be enough without any removal.

Common mistakes

• Grouting over old grout — The new layer is too thin to bond properly and crumbles out within months. Rake out to at least 3mm first.
• Using grout in corners and where tile meets bath — Those joints flex, and rigid grout cracks immediately. Flexible silicone sealant is the correct material there.
• Wiping too early — It pulls the fresh grout back out of the joints and leaves them hollow. Wait fifteen to twenty minutes.

Questions people ask