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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Bridget

Hi! Found the old 1927 hexagon tile in my home. There was a vinyl floor over it then tile over that. The grout is filled with the brown tacky glue that held on the vinyl. Any suggestions for removing it? Also, to re-grout how much old grout should I remove? As you know, the tiles are very small and there’s a lot of grout. Thank you! ~Bridget

Reply

Roger

Hi Bridget,

You are in for a treat! Just kidding, that’s gonna suck. The only way to remove the glue is to scrape it out of there. The grout should be removed to 2/3 the depth of the tile for the new grout to bond properly.

Reply

Tammie

Hello. I now know my tile was installed with no subfloor. There is one particular area that the grout is cracking. I realize the floor likely needs replaced, but looking for a temporary fix for now. Would adding sealant to the grout help it stick better? We have tried removing the remaining areas of grout and re applying, but it doesn’t seem to last.

Reply

Roger

Hi Tammie,

A temporary fix would be to remove the tile and use thinset to reinstall it. You need to eliminate the movement of the tile if you want your grout to stop cracking.

Reply

Kimberly

Roger,
My story is a nightmare that would take forever to write…..However, here is my long story short….. My tile “expert” had no clue what he was doing and my floor is an uneven mess! It has been almost two weeks now and my contractor (who I love inspite of this nightmare) wants to come back and just “go over it with more grout”, feeling this will solve the problem. After reading some of the above comments I have my concerns that this is just a quick fix and I will encounter problems down the road. Should I allow this? There is some question as to if the liquid sealing adhesive was added to the grout mixture or not (installer says it was). Would this make a difference in your answer to me?
Thank you,
Kimberly
A single woman who is feeling taken advantage of these day.

Reply

Roger

Hi Kimberly,

If the tile is an uneven mess then no, grout will not fix it. If the grout is what is uneven then the existing grout needs to be removed first.

Reply

Kimberly

Roger, Thank you so much for responding so quickly. One of my biggest concerns at this point is …..since the floor has been down for two weeks now and I am assuming the grout has cured. If they go over the top of it with more grout, will the new grout stick? Or, am I just going to be looking at another mess down the line. As I mentioned in my above post, there is a question as to if there was a liquid sealing adhesive added to the grout mixture, so I’m wondering if that would make a difference as to if the new grout will stick or not. Thank you again!!!!!
Kimberly

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Kimberly

Additionally…….I’ve read that under no circumstances should you go over grout that is more that 2-3 days old with out taking the grout out because “grout does not stick to grout it” ….it is meant to stick to the sides of the tile. Is that correct?

THANK YOU AGAIN!!!!!!

Kimberly

Reply

Roger

That is correct. Grout bonds to the sides of the tile, that’s why the old stuff needs to be removed first.

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