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.

Previous post:

Next post:

Vickie

Hi – It’s me again; I have another question. We have decided to enlarge a room that has a tiled floor. I am hoping to get my hands on the same tile, so that when we extend 2 of the walls of this room, we can continue with the same floor tile. My question is this: how do we prepare the current edges of the floor tile to accept the new tile? I hope I am making sense.

Reply

Roger

Hi Me Again,

Just remove the grout from between your existing tile and any that you remove. If you have full tiles along those edges you don’t need to do anything special to them.

Reply

Amber

We just recently built a new house and we have noticed several bubbles and cracks in the grout of the showers. The builder is sending someone out to fix it for the 2nd time. I’m just wondering what should I be making sure they do to insure it is fixed correctly?

Reply

Roger

Hi Amber,

That depends on why it’s doing that. The likely reason is lack of waterproofing. If that’s the case then nothing short of a full replacement will fix it permanently.

Reply

steve

We had a guy do a tile bathroom and the grouting has some gaps / missing areas that we want filled in. The grouting was done a couple days ago and has not been sealed. Is it ok to add more grout or should it be removed. I know as a general rule you want to remove old grout but i was just wondering if that changes since the grout is so new and has not been sealed.
thank you.

Reply

Roger

Hi Steve,

Since it’s just a couple of days old you MAY be able to get away with just adding more grout. I can’t guarantee that, though. It would be better to remove the affected areas and regrout.

Reply

Leave a Snarky Remark

***PLEASE READ THIS FIRST!***

If you have already posted a question about your project and you are leaving an additional comment or asking another question - please do so as a reply to my answer to your last question.

Below every comment is the phrase 'Please click here to reply to this comment', just click on that and leave your next question.

If you post an additional question here it will show up as a new topic and thread. I have over 15,000 comments on this site (seriously), I can not go through every one to find the project or question you may be referencing.

HELP ME HELP YOU!

Thanks.

;) :wtf: :wink: :whistle: :twisted: :suspect: :shades: :roll: :rockon: :oops: :lol: :lol2: :lol1: :idea: :guedo: :evilb: :evil: :eek: :dance: :cry: :corn: :cool: :censored: :bonk: :arrow: :D :?: :-| :-o :-P :-D :-? :) :( :!: 8)