Filling Grout Lines with More Grout

by Roger

When there is a significant amount of movement on the substrate of a tiled floor or wall it may lead to grout cracking. When this happens it will leave what looks like a crack in the grout where it has come away from the tile. Unless your grout was installed very recently this is always due to movement in the tile. If your grout is new it may be caused by incorrectly mixed grout. With grout that has been doing this for a while it may lead to whole chunks of grout coming loose and leaving large voids in your grout lines.

While it may be tempting to simply mix up some more grout and fill these voids you need to know that it will not last. If you do this it will fill the grout lines just like new but over time will lead to the same problem. Grout over grout is not a permanent solution.

Why it won’t last

The first reason is that when you go over the top of grout that is already cured with new grout, there is no adhesion to the old grout. It will instead simply create a layer of grout on top of the old grout. These layers have no way of  sticking to each other. When you grout tile the grout actually sticks to the sides of the tile rather than whatever substrate is beneath it. While it will stick to the substrate at the bottom of the grout lines to an extent, it is not a permanent bond. Attempting to grout over the top of old grout is simply stacking two seperate layers of grout. It will always remain two seperate layers.

The second reason is no matter how much of the old grout you may take out to install new, if you do not fix the actual reason the grout failed in the first place, eventually the same thing will happen again. As with any problem you may encounter with a tile installation, you must figure out the initial cause and fix it to prevent repeated problems. This is an involved process which I will cover in a different article. For now I’ll stick with the solution for the grout problem.

What to do

Rather than simply filling the grout line where the grout is missing, you must remove the old grout at least 2/3 the depth of the tile so the new grout has a feasible surface to grab onto. The easiest way to do this is with a grout saw. Ideally you would remove the old grout all the way to the substrate before regrouting it, but 2/3 will be sufficient if it is difficult to remove.

You need to remove any of the old grout that seems loose or has come loose from the sides of the tile. You also need to make sure the spot where the new grout butts against the old is a 90 degree angle, or close to it. In other words from the top of the grout line straight down. You do not want a slope. Eventually a slope must be feathered to a very thin edge. That will be the first place it will fail again, any very thin layer. A 90 degree angle prevents that.

It is also better to make the transition from old grout to new in the middle of a grout line rather than at one of the corners of the tile. The grout line at the corner of the tile has six different spots it can fail, the middle of a grout line has only one. It lessens the chance of failure.

After you remove the sufficient amount of the old grout just mix some new grout and fill the lines. You must make sure you force the new grout into the grout lines very well. You want to make certain there are no voids and the lines are full.

The above method will work to temporarily fix your cracking grout. As I pointed out above, you must find the initial reason for the grout failure before a permanent fix will last. It’s difficult to say how long this fix will work, it may be two weeks, it may last a year. That depends on the severity of the problem that caused it. It also depends on the application (wall or floor) and how much use it gets. A floor in your main entryway will not last as long as a shower that is never used.

You should also take into consideration the age of the grout. If you are repairing grout that has been installed for five years, the new grout, even if it is the same brand and color, will not likely match perfectly. The best solution, of course, would be to fix the cause of the cracking and regrout the entire floor. Depending on what you’re fixing and why this method may solve your problem.

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Kevin Stock

Hi Roger. Four days ago, my contractor grouted my new floors, but washed away too much of the grout. Is it too late to just add another layer to make it more flush with the tile? Btw, the day after it was done, I asked the contractor if it can be done, and he said no, that the grout was already rock hard. Thank you.

Reply

Roger

Hi Kevin,

Anytime up to 28 days when the cement crystals are fully hydrated.

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Kevin Stock

Wow! Thanks Roger. I thought the window for adding more sanded grout was only 2-3 days. Shall I tell my contractor he has just under a month to add another coat of grout? That would be much preferable than trying to take it all out. The lines are 1/16″ so I was told it would be next to impossible to remove the grout without damaging the glazed porcelain tile. Thanks again!

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Kevin Stock

Oh ya, yes I said he used sanded grout on 1/16″ grooves. Even the bag says it’s for 1/8″ or wider. It feels not only too deep (washed out) but also very coarse. The grooves are a complete dust trap. I used black grout, but it looks like I used white because of the dust! Should he have used non-sanded grout or is he ok to choose whatever he’s comfortable with? On the day of grouting, I suggested non-sanded grout and he said no.

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Kevin Stock

Here are a couple of photos. I repeatedly asked for high grout lines in order to achieve a unified, almost poured concrete look. The tiles are beautiful and they were laid well, but the grouting was clearly an afterthought. The contractor is willing to do another coat, but he says it’ll probably chip off. He asked me to research what coating I’d like to put on top. I was thinking maybe epoxy grout, since it’s like plastic and tends not to chip. What would you do if you were me?

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Kevin Stock

This one shows the black grout looking white.

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Jamie

I just did one layer of grey grout to my backsplash with the new trend of grey color….I hate it.

Can I just go over the grey grout with white? Or do I have to grout saw it? Will this ruin my new subway tile??

Thanks!

Reply

Roger

Hi Jamie,

You can, but it won’t be white, the gray will show through in areas and it will likely flake off over time. You need to remove the gray. No, it won’t ruin your subway tile.

Stop following trends. :D

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Christina

Hi,
I need some help. My husband and I just paid a lot of money to have a flooring company lay wood plank tile through out our downstairs (1200 sq ft). Needless to say they did an awful job and I’ve basically fired them. The tile isn’t completely level at the grout lines, there are holes in the grout where there were probably bubbles while they were grouting, and the grout lines aren’t the same sizes – plus some of the grout is sitting on top of our tile. In some areas I can still see the side of the tile itself and to make it worse I ordered brown grout to match the tiles and they put down gray. Now its on us to fix this mess.

Besides tearing it up and redoing the tile – do I need to drill out all the current grout lines before i regrout the tile? The floors have only been down for about 2 1/2 weeks so its still new. Any advice you have is greatly appreciated.

Thank you

Christina

Reply

Roger

Hi Christina,

If it is over about three days old you should scrape out the existing grout before filling it with more grout. Grout bonds to the sides of the tile, not the substrate beneath it, which means it has trouble bonding to existing grout and remaining stable. You can try to grout over it, but I’m afraid it will begin to sheer off after a couple of weeks.

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Andrea

Hi Roger,

Our 1953 casita was remodeled with 12 x 24″ tiles through the 700 sq ft. The LR is on cement, but the bedroom was on a subfloor (after we ripped off the carpet and then the old, laminate, original tiles). The tile was installed, looked great, but nobody stayed there as it took awhile to pick out new furniture.

After a few months, someone stayed there for two weeks and two of the tiles had cracked grout around them. That is when I asked the contractor to come over and they said that there is movement. When you stand shoulder width apart and shift your weight you can feel the floor move. We have cracked grout on a few tiles. The tile guy said he’d re-grout and if it happened again, he’d come back. As you predicted it has broken down again and looks like crap…and the tile guy is ignoring my calls.

It sounds like you’re saying that I have to rip it up and retile! That’s the only option? Ugh! This tile wasn’t cheap. Maybe I’ll have to carpet the whole bedroom to cover up the crappy tile job instead. Hugely disappointed! How about a grout that has rubber in it? A malleable grout? Something else besides “rip it up”?

Reply

Roger

Hi Andrea,

Sorry, no such animal. Unfortunately that is the only long-term solution.

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Josh

I grouted a river rock shower floor 2 1/2 weeks ago. I haven’t done anything with it since as I have been waiting for the shower door to arrive. I have noticed that there are a couple of areas where I wiped too much grout out, causing low spots. Is it too late to just add additional grout over the top? If not, how do you suggest doing it? Just the low spot or the low spot and surrounding area for it to blend better?

Reply

Roger

Hi Josh,

You should be able to go over it just fine. Do the low spot and a portion of the surrounding area to blend it.

Reply

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