How to Replace Moldy Grout

When grout becomes discolored, cracked and chipped, it's time to replace it. Follow these step-by-step instructions to learn how.

By: Ben Breslerman
Related To:
Grout Maintenance Repairing Masonry and Tiling Bathroom Tile Bathroom Tile Kitchen Tile Kitchen

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Sick of 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

Saw Out the Mold

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

Vacuum Loose Residue

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

Clean Grout Joints

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

Mix the Grout

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

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.

Clean the Tiles

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

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

Clean Dry Grout

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

Apply Grout Sealer

Follow the manufacturer’s instructions for applying grout sealer. If you follow the directions, you should never have discolored grout again.

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