How to Treat Old Grout So That New Grout Will Stick

Grout starts out as a powder.  When mixed with water, it fills in the gaps between ceramic tiles.

It hardens and gives the grooves between the tiles a smooth and water-resistant surface.  Over time, the grout requires replacing because it starts to crumble, discolor or crack.

Treating the old grout with the proper tools enables the new filling to stick and provides a long lasting surface for the grout wall or floor. 

1. Place a drop cloth or old sheet over the areas in the room. Removing grout is a dusty, messy job. Empty the room of unnecessary decor or other furnishings.
2. Wear safety goggles and a dust mask to prevent breathing the dust or getting debris in your eyes.
3. Remove the old chipped, stained or cracked grout with a grout scraper and grout saw. Look for these tools at hardware and home supply stores. A grout scraper may be all that is necessary if the area is small.
4. Scrape out the old grout to a depth of at least 3 or 4 mm. This enables the new grout to stick well. Apply masking tape to the tile edges to avoid nicking the tiles when using the grout saw.
5. Vacuum the area several times to ensure you remove all the dust and grit. A clean surface is vital to the ability of the new grout to adhere well.
6. Wet a cleaning cloth and wring it out well. Wipe out the gaps between and around the tile to ensure the surface is clean and dust-free before applying the new grout.

Tip

Rent or borrow a grout saw if you do not want to purchase one.