How to Fix Cracked Shower Grout

Grout is the unsung hero of your shower enclosure, acting as the primary barrier that prevents water from reaching the wall structure behind your tiles. Over time, house settling, moisture expansion, and simple age take their toll, leading to hairline cracks that invite mold, mildew, and eventually water damage to your drywall or backer board. Ignoring these small fissures is an invitation to much larger structural problems. Done well, a grout repair looks seamless and makes a decade-old shower look like it was finished yesterday. The secret lies in removing enough of the old material to allow the new grout to lock into place securely. Don't simply smear new grout over the old cracks; that is a temporary patch that will fail within months. Invest the time in proper removal and preparation, and you will have a watertight seal that lasts for years.

  1. Cut Out the Damage. Use a grout saw or a carbide-tipped oscillating tool blade to carefully cut out the cracked and loose grout. Aim to remove at least 1/8 inch of depth to provide enough space for the new material to bond.
  2. Vacuum Every Crevice. Vacuum the joint thoroughly to remove all dust, grit, and loose particles. Follow up with a damp cloth to ensure the edges of the tiles are completely clean and dry before moving on.
  3. Mix to Peanut Butter. Mix your high-quality, mold-resistant sanded or unsanded grout—depending on your joint width—according to the package instructions. Aim for the consistency of smooth peanut butter.
  4. Press Grout Deep. Use a rubber grout float held at a 45-degree angle to press the mixture firmly into the joints. Work in diagonal strokes to ensure the gaps are completely filled without pulling the grout back out.
  5. Wipe and Shape. Wait about 15 to 20 minutes until the grout feels firm to the touch, then use a lightly dampened grout sponge to wipe away the excess. Rinse the sponge frequently, keeping it only damp, never soaking wet.
  6. Let It Cure Fully. Allow the grout to haze over, then buff away the remaining film with a clean, dry microfiber cloth. Let the grout cure for the duration recommended by the manufacturer before getting it wet.