How to Replace Moldy Grout

Here's what you need to fix it: 1. Grout saw 2. Vacuum or soft brush 3. Abrasive cleaner 4. Rags 5. Grout (non-sanded for joints smaller than 1/8-inch, sanded for 1/8 or bigger) 6. Float 7. Citrus-based cleaner 8 Grout Sealer

Working in one 2-by-2-foot area at a time, run the saw up and down the grout line.

Vacuum out flaked residue, or use a soft brush to remove the grout pieces.

Put some abrasive cleaner on a wet rag and rub the joint to remove any remaining residue.

Carefully follow the directions regarding the proportions of water and dry ingredients because grout won’t last if it’s too wet when mixed.

Lay the grout in the joint with a float, filling the space generously. If you don’t have a float, make a tool with a piece of cardboard and a putty knife. If you’re doing a horizontal surface such as a countertop, work from the back forward. If doing a diagonal surface, work from the bottom up. If you start at the top, the grout will have a tendency to sag in the channel.

After the wet grout has set for about five minutes, clean up the tiles with a wet sponge. With a dry rag, carefully wipe only the tile. The grout will set in about 20 minutes and cure in 24 hours.

Add a “skim coat” after the first application has dried. This will fill in any tiny holes.

Clean the dried grout before sealing it. Use a citrus-based cleaner because bleach will discolor the unsealed grout.