Map the problem
Note whether the crack crosses only one tile or continues through several tiles or grout joints. Check whether a tile moves under gentle foot pressure or sounds hollow when tapped lightly. Look for gaps at walls or transitions. Do not pull up tile just to diagnose it; removal can damage adjacent pieces or waterproofing.
Check for water before replacing shower tile
In a shower, staining, soft wall material, a persistent musty smell, or moisture outside the enclosure deserves attention before cosmetic work. Grout and tile are the visible finish; the waterproofing assembly underneath is what protects the building. A replacement tile or fresh grout alone does not correct a failed waterproofing system.
Match the repair to the cause
A single damaged tile on a stable, dry surface may be replaceable if a matching tile is available. Repeated cracks, multiple loose tiles, or movement at the substrate call for a wider assessment. Tile systems need a suitable substrate and movement accommodation; Schluter identifies movement as a common source of cracks.
Prepare for a useful service visit
Save an extra tile if you have one. Share photos of the full area and a close-up, the approximate age of the installation, and whether the problem is worsening. This helps us distinguish a spot repair from work that needs the underlying surface addressed.
Technical reference: Schluter: three reasons floor tile cracks ↗