If the grout in your shower corners keeps cracking no matter how many times you fix it, it isn't bad grout. It's the wrong material for that joint. Inside corners and changes of plane move slightly every day as the house and the shower expand and contract. Rigid grout can't flex, so it cracks.
THE RULE
| Joint | Use |
|---|---|
| Flat joints between tiles on the same wall | Grout |
| Inside vertical corners where two walls meet | Flexible sealant (caulk) |
| Where the walls meet the floor or tub | Flexible sealant |
| Around the valve, niche edges and glass | Flexible sealant |
Tile industry installation standards call for movement joints at these changes of plane. Filling them with grout is a very common shortcut, and the main reason corner grout fails.
WHICH CAULK?
- 100% silicone: the most flexible and waterproof; doesn't take paint. The usual choice in showers.
- Color-matched sanded caulk: made to match grout color and texture; looks seamless.
- Avoid basic acrylic latex caulk in wet areas. It shrinks and lets go.
HOW TO REDO IT
- Cut out the cracked grout or old caulk completely with a grout saw or utility knife.
- Clean the joint and let it dry fully, ideally 24 hours with no showers.
- Wipe with rubbing alcohol so the sealant bonds.
- Tape both sides of the joint with painter's tape for a straight line.
- Apply a continuous bead, tool it smooth, pull the tape, and let it cure before using the shower.
Cracked corners plus loose tile, soft spots or a musty smell may mean water has already gotten behind the tile. That's no longer a caulk job; see what happens behind the tile.
Redoing shower caulk is a small handyman job. For full shower replacements, see our shower remodel cost guide.
RELATED READING
SHOWER WATERPROOFING: BEHIND THE TILE
Membranes, pans, flood tests, and the questions to ask before anyone sets a single tile.
WHAT GROUT COLOR FOR WHITE SUBWAY TILE?
White, gray, charcoal or black: how each looks, what hides dirt, and grout that stays clean.
SHOWER REMODEL COST IN THE DMV (2026)
Prefab vs. custom tile, glass, valves, and the hidden line items that move the final number.
Planning a project? See our Bathroom Remodeling service page for scope, process and recent work.
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