Why the adhesive decides
Tile adhesive has to set and release most of its water before grout goes over it. If grout is pushed into joints while the adhesive underneath is still soft, the tiles can shift slightly as the grout is worked, and moisture trapped behind the grout slows the whole bed from curing. The result is grout that cracks along the joint, tiles that sound hollow, or a white bloom on the grout surface.
Every adhesive bag states a time before grouting. That figure is the starting point, not a target to beat.
What makes it take longer
Cold rooms slow curing, so an unheated bathroom in winter can need longer than the bag says. Large-format tiles and porcelain, which absorb almost no water, hold moisture in the bed longer than a small porous wall tile. A thick adhesive bed, used to level an uneven floor, takes longer than a thin one.
The surface behind matters too. A tanked wall or backer board does not soak water out of the adhesive the way bare plaster does, so the bed dries mainly outwards through the joints.
Floors need more patience than walls
Floor tiles carry weight, and walking on them before the adhesive has set can break the bond under a corner, which later shows as a cracked tile or a hollow sound. Most floor jobs are left untouched until the adhesive is ready to be walked on, then grouted.
If the floor was screeded first, the screed itself needs to be dry enough before any tiling starts. That is a separate wait, and our expert guide on screed and drying times covers it.
Grout or silicone first?
Grout goes first, into the joints between tiles. Silicone sealant goes last, into the movement joints where two surfaces meet: tiles to bath, tiles to shower tray, and internal corners in the wet zone. Those junctions move slightly, and grout there cracks; silicone flexes.
The grout also has its own curing time before the shower takes daily water, and the sealant needs time to cure before it is soaked. Using the shower too early is the other common cause of early failure.
Signs it was rushed
Grout that cracks in a straight line along the joint within the first months, grout that powders when rubbed, or patchy colour across a wall can all point to grouting before the adhesive or the grout itself had cured. Hollow-sounding tiles in a new job are another clue.
The fix is raking out and regrouting the affected joints, and, where tiles have lost their bond, lifting and rebedding them. If water has been getting behind for a while, the wall or tanking beneath needs checking before retiling.
Doing it once, properly
On our tiling and bathroom jobs, curing times are built into the programme rather than squeezed out of it, which is part of why a full bathroom takes the days it does. If you have grout failing in a shower, send close-up photos of the joints and a wider shot of the wall. We give fixed written quotes after seeing it, quotes are free, and we work Monday to Friday, 8am to 6pm.