The answer is, yes, it is possible to put new grout over old grout.
You may not need to remove most of the grout. It may be possible to apply new grout over old grout without removing it at some places. However, where the grout has deteriorated heavily through crumbling or become too dirty, it is best to remove it before applying new grout.
Let the first coat dry for an hour before applying a second coat. Depending on the grout sealer you choose, allow 24 to 48 hours for the second coat of sealer to cure. After the second coat completely dries, test the surface with a few drops of water. If the liquid beads up into droplets, you do not need another coat.
You can apply new grout right over the top of the old grout. To do this, all you need is a grout removal tool. Use the tool to strike out the old grout, making sure the depth is at least 2mm, which is about the thickness of two dimes stacked one on top of the other.
You don't have to remove all of your old grout to apply the new grout. The new grout can be applied right over the top of the existing grout. You will need a grout removal tool, which is a small tool with a sharp blade capable of chipping away the grout.
Ideally, the final wipe-down will take place after the grout has been allowed to cure for 24 hours. However, grout haze could still potentially be removed within a few days. When it becomes impossible to remove with a sponge, it's time to call The Grout Medic for tile cleaning to eliminate the grout haze.
Grout sealers will break down over time, so you're going to have to reseal grout on a floor every three to five years. Shower grout should be resealed once a year. Always clean grout carefully before doing this resealing.
It is very advantageous to grout the next day as grouting to early will possible move the tiles making them uneven. As the others have said I would always grout the next day, As you don't want the tiles to slip if the adhesive isn't set.
Though small areas can be regrouted, grout removal is still required. The Grout Medic of San Diego Metro's re-grouting service is perfect for small areas of tile, or even small areas of damage on an expansive area of tile.
Regrouting can be a worthwhile home improvement project that keeps your floors looking good as new. It makes your tiles more resistant to mould, prevents water from seeping behind the shower floors and walls, and ensures they have a longer life span.
Carbide blades are the go-to for most grout removal tools as they are both moderately priced and hard enough to handle the toughest grout. Tungsten steel blades are harder and pricier than carbide options but they work fast and are especially good for dealing with a lot of epoxy grout.
Moisture and direct water contact contribute to grout deterioration over time, and eventually, the tiles will crack. This is why you should consider regrouting shower tiles every six months.
Grout doesn't last forever. You can expect a lifespan between eight and sixteen years. Its lifespan will vary depending on how you treat your shower. Odds are, you have no idea when your grout was installed.
Signs Your Grout Isn't Sealed or the Seal Is Deteriorating
If you notice your tile grout is changing color, specifically getting darker when it's wet, you can be pretty sure the seal is broken and needs to have some grout sealing reapplied by a professional.
Grout haze is a byproduct of tile installation, during which the entire surface gets covered with grout. When the excess has not been properly cleared from the tile surface, what little that remains will eventually dry out, leaving behind a dull white film of just minerals.
Will Grout Haze Eventually Go Away? Yes, eventually grout haze goes away but you need to take special measures. Just by diligently wiping down the surface with a wet sponge, the haze will remain and won't come off.
If you notice a haze of grout left on the tiles post installation, either buff it off with a dry soft towel or undertake one final clean. Grout Haze is generally easy to remove within 48 hours of grout application.
The grout should be dug out a minimum of 3mm deep (preferably deeper) so that new grout can have a firm base and a larger surface area of the sides of the tiles to adhere to. Do not attempt to apply new grout over the damaged existing grout.
To repair uneven tiles, you need to remove the tiles and repair their base. Once you reset the tiles, you need to regrout them. Use grout that matches the original to make the repair less obvious.
The main cause for this variation in color is uneven drying of the Portland cement in the grout. There are jobsite conditions and factors which create the conditions for uneven drying and improper cement hydration.