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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I just had a new porcelain tile laid in my kitchen. I’ve had the tile man back because some tiles were raised some not (an up and down effect). I also told him there didn’t appear to be enough tile because 99% of the tiles are not flush with the grout. He only fixed the up and down tiles but I have a large floor and he said to replace all the grout would be a huge job. Now I have dirt traps because the grout is not flush with the tile. In reading some of the other people’s experiences I can’t add grout to what I have. I haven’t put the sealant on yet because it’s not been 72 hours. Is there an easy fix here? Where there’s no sealant and I do still have tile for grout to adhere to, can I grout on top of the newly laid grout?
I’m pretty disgusted with myself right now. I thought grouting was going to be easy, heres what happened. I bought 1/2 gal. of the already mixed grout in a 1/2 gallon bucket made by TEC. Applying the grout with a float started OK but removing and cleaning the tile as I progressed is where I had trouble. The grout didn’t wipe off with a damp sponge like I expected. I turned creamy and smeared all over the tile. At first I thought this was normal and thought I could clean it off later. As I got to the end of the job (approx.75 sq. feet) I realized the grout left on the tile is setting up quick and not wiping off easily. I began to panic and pretty much aborted the grout job and went into “save the tile mode”. The directions on the bucket said not to use too much water while cleaning because it may lead to the grout cracking later. I found I didn’t have a choice. I soaked the tile pretty good trying to make the grout wipe off easier and spent the next two hours scrubbing with a sponge and a little scrub brush to make the tile look as it did before I grouted. The tiles have a haze to them and the grout got in all the nooks and crannys. I kept filling the bucket with clean water to take the haze away. It’s drying now, and the jourey is out on what it’s going to look like in the morning! I know in my haste to clean the tiles I removed too much grout , I’m guessing 1/16 to an 1/8″ shallow grout lines. From what I just read above that means I need to remove 2/3 of the depth of the tile and grout again. In a nutshell THAT SUCKS!!!!!! Can you tell me where I went wrong and is the prognosis to regrout the whole floor?
Hey Matt,
If it’s TEC Invision grout you’re actually fine, as strange as that may sound.
The reason I say that is that Invision is a urethane-based grout with which you can actually go over what you have there to fill the grout lines, without scraping any out, and it will bond just fine. The trick to that stuff is to grout about six square feet and wipe it off, don’t let it set. You won’t hurt that grout at all by cleaning it immediately. Just go over it in the morning and fill all those grout lines.
If you can’t get all the haze off you need some ‘Banish’ which is a latex haze remover made by TEC. You can find it here: Banish grout haze remover
I grouted the newely set tile above my shower today and after the drying of the grout I have noticed lines that are not as full as they should be. Do I have to remove the first grout and regrout or can I put more grout over the top?
You need to scrape those grout lines out (where you need them more full) to at least 2/3 the depth of the tile, then regrout. The grout adheres to the sides of the tile, not what is beneath it.
Shower tile has grout in the corners. Can I remove the grout and replace it with caulk? If so, what kind of caulk should I use? Love your website!
Yes, you can (and should) remove the grout and replace it. Ideally silicone would be the most durable, but sanded acrylic caulk would be fine. Laticrete ‘latasil’ is a 100% silicone that you can get in matching colors for your grout.
Thank you Roger! I will do that. What is the best way of removing the grout when the joint between bathtub edge and the tile is thin?
Thanks.
A razor knife or grout saw. You can get a grout saw at home depot in the tile section.
Hi,
I recently remodeled my bathroom. I put tile on the floor and tiled the whirlpool tub. Now I see I have a slight problem. After I started to use my tub I noticed that grout in the joint when tile meet the tub is cracking. May be because the tub settled a little because of the use. The grout space between tile and the edge of tub is very narrow, so the crack line is almost invisible. I am going to treat all my grout in the bathroom with sealant, so I want to cover this thin crack along the edge of the tub. Can I use sanded caulk to do so? Do I need to remove grout from the space? Again the space between tile and edge of the tub is very thin.
Thank you.
Hi Val,
Any change of plane needs to be filled with a flexible sealant. That area is a change of plane and should be filled with either silicone or caulk. The grout will need to be removed – if it’s under the caulk it will still crack. Yes, you can use sanded caulk – silicone would be better.
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