Is it possible to put new grout over old grout?
A common question in the home is whether new grout can be used over old grout. “No,” is the short answer. New grout cannot be installed over old grout. Grout is used to sealing cracks and joints between tiles and keep them clean, but it does not provide structural support for the tile. Older grouts are frequently made of cement, which has a stronger bond with the tile than newer acrylic-based grouts, but you cannot apply new grout over old grout because it will only make matters worse.
Why can’t you put new grout over old grout?
If your grout is cracked, crumbling, or otherwise damaged, you may be wondering if you can simply replace it with new grout. Unfortunately, this is not an option. New grout will not adhere properly to old grout and will crack and crumble over time. The only way to repair damaged grout is to completely remove the old grout and start over.
What should be done instead
If your grout is looking old and dingy, you might be tempted to simply replace it. That, however, is not a good idea. Instead, here’s what you should do.
To begin, remove the old grout from between the tiles with a grout saw or utility knife. You’ll want to remove as much of the old grout as possible so that the new grout can properly adhere.
Next, thoroughly clean the area with a tile cleaner or household cleaner. Before applying new grout, make sure that all of the dirt and residue from the old grout is removed.
Finally, apply new grout to the area and smooth it in with a rubber float. Allow the area to dry for 24 hours after wiping away any excess grout with a damp sponge.