Symptoms
- Cracks concentrated only at vertical or horizontal inside corners
- Flat wall sections have intact grout
- Cracking recurs after regrouting the same spot
- No cracking issues away from corners
Likely causes
- CommonGrout used instead of caulk at a movement jointCorners, and the joint where tile meets the tub, are designed to flex slightly, which rigid grout cannot accommodate.
- CommonNormal building settling putting stress on corner jointsEven a well-built home shifts slightly with seasons and humidity, and corners are where that stress shows first.
- PossibleGrout applied too thick at the corner originallyExcess grout in a joint that needs flexibility cracks faster than a properly caulked one.
What to do
- Identify all inside corners (where two tiled walls meet, or wall meets tub/floor) with cracked grout.
- Use a grout saw or oscillating multi-tool to carefully remove the cracked grout from these corner joints only.
- Vacuum out all dust and debris from the joint.
- Clean the joint with rubbing alcohol and let it dry fully.
- Apply painter's tape on both sides of the corner joint for clean lines.
- Fill the joint with 100% silicone caulk matched to your grout color, smoothing with a wet finger or caulk tool, then remove the tape before it skins over.
- Leave flat wall grout as grout; only replace the corner and movement joints with caulk going forward.
Tools and parts
- Grout saw or oscillating tool
- Caulk gun
- Painter's tape
Caulk matched to grout colorSearch: “sanded caulk matching grout color”
When to call a pro
Call a tile contractor if cracking is widespread beyond just corners, which could indicate a bigger structural or substrate issue.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.