How can I repair cracked tile grout?

Quick answer

You can repair cracked tile grout by removing the damaged sections to a proper depth, cleaning the joints thoroughly, and regrouting with the correct type (sanded, unsanded, or epoxy). For hairline cracks, a grout repair product or color sealer can work, but anything wider or in wet areas should be cut out and regrouted. At corners and changes of plane, replace cracked grout with color-matched 100% silicone caulk.

What causes grout cracks—and why it matters

Cracks usually come from movement (substrate flexing, temperature swings, or missing expansion joints), improper grout choice for the joint width, or grout that wasn’t mixed/applied correctly. If a lot of cracks keep returning, the issue may be loose tiles or a substrate problem—not just the grout. In showers, cracked grout can let water behind tile, so timely repair is smart.

Tools and materials

• Tools:
  • Grout saw or carbide grout removal tool (manual)
  • Oscillating multi-tool with carbide/diamond grout blade (faster)
  • Utility knife, margin trowel, rubber grout float
  • Buckets, mixing paddle or margin trowel
  • Sponge, microfiber cloth, shop vacuum, stiff nylon brush
  • Caulk gun (for silicone) and painter’s tape
• Materials:
  • Matching grout: cementitious (sanded/unsanded), epoxy, or ready-to-use
  • Color-matched 100% silicone caulk (for corners and edges)
  • Penetrating grout sealer (for cement grout)
  • Mild cleaner, clean water
• Safety gear:
  • Safety glasses, N95 dust mask/respirator, cut-resistant gloves, knee pads, hearing protection (for power tools)

Choose the right grout

Joint width guide:
- < 1/8 in (3 mm): Unsanded cement grout
- 1/8–1/2 in (3–12 mm): Sanded cement grout
- Epoxy: Follow manufacturer; good for stain/water resistance
Minimum removal depth for repairs:
- ≥ 1/8 in (3 mm) or about 2/3 of the tile thickness, whichever is greater

Match the color and type to your existing grout. For wet areas, epoxy or high-performance ready-to-use grout can reduce future issues, but only if the substrate is sound.

Step-by-step: Small crack vs. cut-out-and-regrout

A) Hairline cracks (cosmetic, non-wet areas)

1. Clean: Scrub with mild cleaner, rinse, and dry.
2. Apply grout repair product or color sealer: Work it into the crack with a gloved finger or small rubber float.
3. Wipe and cure: Follow label timing. This is a short-term fix; if the crack returns or is in a shower, do a proper cut-out and regrout.

Time/cost: 30–60 minutes for a few joints; $10–$25 for repair/sealer.

B) Proper repair: Remove and regrout

1. Inspect for loose tiles: Tap tiles with a wooden handle. Hollow or drummy sounds suggest loose tiles. If many are hollow, address the substrate or call a pro before regrouting.
2. Protect and prep: Mask adjacent surfaces, cover drains, and turn off HVAC in the room to minimize dust spread.
3. Remove cracked grout: Use a grout saw or oscillating multi-tool. Keep the blade centered to avoid chipping tile edges. Remove to at least the minimum depth listed above. Vacuum debris.
4. Clean joints: Brush and vacuum, then wipe with a barely damp sponge. Joints must be dust-free and dry.
5. Mix grout: For cement grout, add water per bag directions to a peanut-butter consistency, mix, let sit (slake) 5–10 minutes, remix without adding water. Ready-to-use and epoxy: follow manufacturer instructions.
6. Pack the joints: Using a rubber float at a 45° angle, force grout deep into the joints. Work diagonally across tiles.
7. Initial clean: After the grout begins to firm (typically 10–20 minutes), wipe diagonally with a damp—not wet—sponge. Rinse sponge frequently. Avoid overwashing.
8. Second wipe and buff: When a light haze remains, wipe again and buff with a microfiber cloth.
9. Cure: Keep dry and avoid traffic.
   • Cement grout: Light foot traffic after ~24 hours; full cure ~72 hours.
   • Epoxy/ready-to-use: See label; often faster but variable.
10. Seal (cement grout only): After 48–72 hours, apply a penetrating sealer; wipe off excess. Don’t seal epoxy.

Time/cost: A small bathroom floor (40–60 sq ft) takes 2–4 hours of labor plus cure time. Manual tools $10–$30; oscillating tool $70–$150 + blade $15–$25. Grout: $15–$25 (10 lb bag) or $20–$40 (ready-to-use quart); epoxy $45+.

Corners and edges: Use silicone, not grout

Cracks at tub edges, shower corners, or where walls meet floors are common. These are change-of-plane joints and should be flexible.
- Remove the old grout/caulk completely.
- Clean and dry the area.
- Tape both sides of the joint.
- Apply color-matched 100% silicone, tool it smooth, and remove tape immediately.
- Allow full cure per label (often 24 hours) before exposing to water.

Safety and best practices

• Wear eye and respiratory protection; grout dust is abrasive.
• Go slow with power tools to avoid chipping tile.
• Mix small batches so grout doesn’t stiffen before use.
• Use minimal water during cleanup to prevent color washout and weak joints.
• In showers, wait at least 72 hours before heavy use after cement grout; check product guidance.

Common mistakes to avoid

• Not removing enough grout. Shallow fill won’t bond well and will crack again.
• Using the wrong grout type for joint width or area.
• Overwatering during cleanup, which can fade color and weaken grout.
• Grouting corners instead of using silicone.
• Ignoring hollow tiles or substrate movement; regrouting won’t fix structural problems.

When to call a pro

• Multiple hollow or loose tiles, or noticeable floor flex.
• Widespread cracking that returns quickly after prior repairs.
• Wet-area failures with signs of moisture behind tile (musty smell, darkened grout, soft drywall).
• Natural stone installs, heated floors, or epoxy grout if you’re unfamiliar—these benefit from experienced hands.

With the right tools, careful prep, and correct grout choice, localized grout repairs are very doable for DIYers. Take your time on removal and cleanup—good bonding and a long-lasting repair start there.