Carbide-blade grout saws are used to remove failing grout.
The process of removing old grout and filling the cleaned joints with new grout is the same for most ceramic and porcelain tile installations (including floors, walls, and countertops). For improved adhesion and waterproofing, use a polymer-modified grout mix.
It’s important to note that regrouting is an appropriate repair only for tile that is securely bonded to its substrate. Several loose tiles in one area indicate that the mortar has failed or there are problems (usually moisture-related) with the substrate. If multiple tiles are loose, retiling the floor may be your only option. If a tile job is generally in good shape and you can find a perfect color match with your old grout, you can regrout only the affected areas. Otherwise, it will look best to replace all of the grout within an area.
Carbide-blade grout saws are used to remove failing grout.
Failed grout allows water underneath tiles, which causes the damage to spread rapidly. If the grout lines in your tile floor are crumbling or a few tiles are loosened, the best solution is to regrout the entire floor.
HOW TO REGROUT FLOOR TILE
Scrape out the old grout with a grout saw or other tool, being careful not to scratch the tile faces or chip the edges. You may choose to regrout only the filed grout lines for a quick fix, but for more pleasing results and to prevent color variation in the grout lines, remove the grout around all tiles and regrout the entire floor.
Wash the tiled floor with a 1:1 mix of white vinegar and water, paying special attention to the areas around the tile joints. Vacuum the floor first to get rid of all debris.
Apply new grout. Prepare grout mix according to the instructions on the package and then pack fresh grout deep into the joints using a rubber grout float. Hold the float at a 30° angle to the tiled surface.
Wipe diagonally across the tiles and grouted joints to remove excess grout and smooth the joints. Seal the grout joints with grout sealer after they’ve dried for a week or so. Note: Sealing all the grout joints will help new grout lines blend with old grout if you’re only doing a partial regrouting.