Rake out cracked grout, clean the joints, then re-grout and reseal so tiles stay watertight and tidy.
FG-01Match the grout and prep the roomCheck whether the existing grout is cement-based or epoxy, and match the colour as closely as you can. Open a window for ventilation and lay a dust sheet under the area you're working on. Tape off any nearby sockets or switches if you're working near them, just to keep dust out.
FG-02Rake out the cracked groutRun a grout rake or the corner of a flathead screwdriver along the cracked joint, working slowly to avoid chipping the tile edges. Remove all the loose and cracked grout down to the full depth of the joint, not just the surface. Wear safety glasses, as grout dust and small chips can flick up.
FG-03Clean out the jointsVacuum each joint to lift out loose dust and debris. Wipe over with a damp cloth to remove any remaining film, then let the joints dry fully for around 30 minutes before you grout. New grout won't bond properly to a damp or dusty joint.
FG-04Mix a small batch of groutMix only a small amount at a time, following the ratio on the tub. Grout starts to stiffen quickly once mixed, so little and often works better than one big batch for a small repair like this.
FG-05Push grout into the jointsLoad a rubber grout float and drag it across the joints at roughly a 45° angle, pressing firmly so the grout packs in fully. Go over each joint from a couple of directions to make sure there are no air gaps.
FG-06Shape the joints and scrape off excessRun a rounded grouting tool, or a gloved finger, along each joint to give it a smooth, slightly concave finish. Scrape excess grout off the tile face straight away with the edge of the float before it starts to set.
FG-07Clean the tile facesAfter about 10-15 minutes, once the grout has firmed up slightly, wipe the tiles with a damp sponge using diagonal strokes so you don't drag grout back out of the joints. Rinse the sponge in a bucket of clean water often and go over the area two or three times to remove the grout haze.
FG-08Leave the grout to cureLeave the repaired joints for at least 24 hours before letting them get wet. If the crack was near a bath, basin or shower, avoid using that fitting during this time so the grout can set properly.
FG-09Reseal movement joints and tidy upWhere a tiled joint meets a bath, basin, worktop or another wall, that's a movement joint and should be silicone sealant, not grout - if you disturbed any silicone while working, cut it out and reseal it once the grout has cured. Wash your tools before any leftover grout sets on them, and clear away the dust sheet and tape.