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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Angela

Hi Roger,
We have just had our bathroom done and chose to have all walls and floor tiled. When the fitter was fitting the floor tiles I noticed that there were big voids where not tile cement was put (mostly under the corners) he grouted the floor tiles on Tuesday and said the grout had started to crack before the end of the day so added more. He has gone and wont be back until next week and I can see & feel large lumps of grout lifting at the corners. Please can you give me some advice on what action I need to take next? would this be down to not enough cement at the laying stage?

Also I have noticed smallish air bubble holes around our mosaic tiles that were grouted a week ago – he said he is just going to fill these with more grout – do you think this would last?

Thanks in advance.

Reply

Roger

Hi Angela,

If your grout is cracking then yes, it’s an issue with something beneath the tile, not the grout. If he used unsanded grout in your mosaics yes, that will be fine.

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Dre

I regrouted yesterday. I didn’t do a good job and there are areas where there is too much grout and some where I wiped too hard and it is flush with the tile. Do I need to regrout the areas I wiped too hard? Can I add more to the current grout since I did it about 13 hours ago? I did scrape all the old grout before adding the new one. My husband is a marine and he’s on a mission so it’s just me. We put the house up in 48 hours for sale. Please help. I cried after I realized it was a bad idea to do this project. I put the grout on with the float but I wasn’t able to scrape off all the excess. I made the mistake of trying to do the whole shower at once instead of in batches. If I wiped too much grout away does this mean it won’t be water proof?

Thank you
Dre

Reply

Roger

Hi Dre,

Your grout has nothing to do with whether your shower is waterproof or not. You can add more grout if you need to, it will be fine.

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joni kartchner

There are numerous holes showing up in the grout in our floor between tiles after only being installed less than a year. The installer came back and added more grout. We’re still finding new holes. Did he use too much water in the original grout? Thank you for your posts!

Reply

Roger

Hi Joni,

That’s possible, or too much water when washing, or unsanded grout where it shouldn’t be used, or used old grout, or just poor workmanship, or… :D Is it unsanded grout? How big are your grout lines.

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john

Hi Roger,
I have a number of places that the grout colour looks dirty or has become discoloured (foyer floor; bathrooms; kitchen floor; and we have tile counters and island)
I tried the polyblend grout renew (simply a paint job on grout) in my small bathroom and it looks fine. But, it was a tedious job.
I am looking to get the house ready for sale, but i also want it to last.
What do you recommend?
1. polyblend renew the rest of the areas; 2. re-grout (considering the grout is in good condition, do i have to scrape the recommended depth or can i go less)
either choice….should i seal the entire area or just the grout?
also, i want to make sure of your advice…..all corners and where floor (or counter) meet wall must not be grouted but a silicone must be used?
thank you for your help

Reply

Roger

Hi John,

If the grout is in good shape then the renew would probably be best. If you do regrout then yes, you still need to remove it to 2/3 the depth of the tile for the new grout to bond correctly. Yes, all changes of plane (corners, counter meet wall, etc.) need silicone, not grout.

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Dee

I agree with Mike Monroe: thanks for the straight forward info. I recently acquired a home and there is stone flooring which I think is beautiful; however, the grout lines are a bit dingy and nothing will clean them up. I saw an online youtube video with someone using “grout renew” and decided to try that. However, my soon to be son-in-law, who installs floors, said he would apply new grout over the top of the old to ‘cover up the old’ and fill in the grooves where the stone tiles doesn’t exactly line up (they’re uneven in a few spots). I will certainly not be going for the grout over grout option now. Thanks a bunch for sharing!

Reply

Kathy

I just grouted yesterday and my grout lines are way too deep; can I re-grout over this today? I’m thinking maybe because it hasn’t completely cured I’m ok doing this?

Reply

Roger

Hi Kathy,

Yes, you can, up to three days.

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Elizabeth

I started to regrout a few lines in and around my shower and when we removed caulk from the perimeter of the floor and walls corners for the 4th year in a row because it was moldy, I got it in my head to keep going. My intention was nit to redo everything. My contractor told me to stop and grout because the rest was good but I could see small minute areas along the floor that were rubbed away from caulk removal so I kept going. Now I removed the grout from the perimeter of the floor. But grout doesn’t bond to grout and there are so many intersecting lines along the floor and walls. .. Do I need to regrout the entire shower? You mention caulking. Would I caulk this instead or grout and then caulk? I know it was a change of plane but the only reason it started breaking down was because of frequent caulk removal. I don’t know what I am doing. Please advise.

Reply

Roger

Hi Elizabeth,

If you scraped all the grout out of those areas then you can regrout it. It shouldn’t cause any problems.

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Mike Monroe

Thaks for the good straight forward info. Excellent stuff

Reply

Lina

I just put tile on lanai for a week and the grout line wasn’t filled enough can I put more grout on it?
Thank you

Reply

Roger

Hi Lina,

Yes, provided you dig the existing grout out to 2/3 the depth of the tile where you need to install more. You should not just go over it, it will likely crack off, especially in an exterior application.

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Ruth Cervantes

In. My counter in the kitchen i have tiles also as the backsplash the proble . Is that it gets wet often as i wash dishes grout has been craking into piece and water has been seeping through those missing pieces of grout and now i have my cabinet from underneath my sink getting wet how can i fix this problem my husband simply just wanted to put caulking but don’t want that it will look messy and probablynot last

Reply

Roger

Hi Ruth,

Water will soak into tile whether it is cracked or not. That sounds like an awful lot of water, though. There should not be enough water from just washing dishes to get your cabinet beneath your sink wet. Regardless, I would remove the tile from the backsplash, replace whatever soaked substrate you have back there now (likely just drywall) and redo it with backerboard and a waterproofing of some sort.

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Caroline

Hi! I have a corner shower 3′ x 4′ (tiles to the ceiling) and the floor with an area of about 10 sq ft. All the tile is 2″ square (dark blue with dark grey grout). It was put in 23 years ago and done extremely well (with all the cement board, heavy membrane, and whatever else…) . I have not taken care of it at all. There are 2 areas of grout the have come out– about 2/3″ on the floor and about a 1.5″ on the edge of the floor to wall. What now? Chip out the broken and missing areas? Is there a certain way to clean the holes before regrouting? Then how do I clean all the grout so I can resell the whole shower? I would really appreciate any help! Thanks

Reply

Roger

Hi Caroline,

Any grout in any change of plane (corners, where the wall meets the floor, etc.) needs to be removed and replaced with silicone. As to any other grout that is cracking it normally indicates movement of some type. You really should figure out what is causing that portion before attempting to replace it or you may just end up with the same problem.

Reply

John Inglis

Hi Roger

I am going to replace the group in my tiled areas.

Since the grout sticks to the side of the tiles it was suggesed to me that i could scrape the grout down about 1/8 of an inch between the tiles.

Then when the remaining grout was grouted over it should work became some of the sides of the tiles will be showing for the new grout to stick too?

Does this make sense to you?

Thanks in advance
John

Reply

Roger

Hi John,

To regrout you need to scrape down to 2/3 the depth of the tile, not just 1/8″. This gives enough bonding surface on the sides of the tile for the new grout to bond.

Reply

Ashley

We have some loose and cracking grout in our backsplash in our kitchen. It is primarily where the stone backsplash meets the granite countertops. The worst area is along the wall where the sink is. This is also an exterior wall. What can we do to fix it without hurting the countertop? The tile is about 1 1/2 years old. Thanks!!!

Reply

Roger

Hi Ashley,

A change of plane isn’t supposed to be grouted, it’s supposed to be siliconed.

Reply

Jackie

Hi Roger,
I have a newly done bathroom and I have a few concerns. The first is the grout has cracked around the door frame where tiles meet it, this was filled with grout. The cause is likely due to the architrave being fitted post tiling to the outside of the door, lot of banging in nails, etc. I have read your solutions above and I am thinking that I should cover/mend with a similar coloured silicone sealant for flexibility but do I need to take out all grout first?

The grout in the wall tiles seems at a low level in that I can see the edges of the tiles, clearly, should I worry about this?

Lastly, I have a gap of about 5-7 mm between the bottom of the architrave and the floor tiles, what would be best to fill this?

Many thanks.

Reply

Roger

Hi Jackie,

Yes, that should be replaced with silicone. It is always best to get all the grout out of it first, it will still crack and crumble behind the silicone, which may debond it.

It doesn’t affect anything except the aesthetics of the installation.

Not really anything you can fill that gap with that will look good short of cutting a fill piece of the same material. Silicone would work, but may not look great, that’s a large gap.

Reply

cj madewell

In the last 24 hours I grouted 2 countertops when I was done I have certain spots almost without grout and some is not smooth can I just make more gr,out and put it on the top again? It is not all the way cured so, is this ok for me.to do?

Reply

Roger

Hi CJ,

Yes, that’s fine.

Reply

Lynne

We just had our bathrooms remodeled and it appears that there are gaps in the wall grout. These gaps look like an oversight by the person who applied the grout. There are quite a few and I am wondering how to fill it. Do I use a bit of the silicone caulk in the same color that they left or do I mix some grout and apply it to all of the gaps? Also, is there a reason that the matching silicone caulk that they used where the wall meets the tub is already cracked and opened up? It has probably been 5-6 months since it was installed and only 3 months of being used.

Reply

Roger

Hi Lynne,

You can mix up more grout and fill it, but if the problem is deeper it may not last. The corners may have cracked because it wasn’t silicone, acrylic caulk tends to lose it’s elasticity over time and shrink, although not normally that quickly.

Reply

paul

Really great info. Been trying to find the answer on grouting over grout for a week now!
You’ve already said above 3-4days before you have to start removing grout to re-grout…But??… Is just over a week pushing it??
Ive protected the floor with sticky backed roll to minimise dirt and dust, It was just that the grout took ages to go off before i could wipe over , in the end it just got silly so we started to clean off the grout a little to early.
Anyway the next day we could see the grout had sunk a little, and is showing the unsightly lines on the edge of the tiles.
It wouldnt be so bad if all the tiles edges looked the same but some are flush some are sunken.

Please come to the rescue!!!!

Reply

Roger

Hi Paul,

You can wet down the existing grout and try to mix up some grout a bit thinner and go over it. It may work, it may not. But if it doesn’t you’ll need to scrape out the grout anyway. May as well try the easier way first.

Reply

paul

Thankyou Roger, great site!

Reply

Ben

I seem to have removed too much grout when cleaning and it seems low in most areas. The grout is not even 24 hours on the floor. Can I add more at this stage? At what point is it too late?

Reply

Roger

Hi Ben,

You should be able to now, you need to dig it out after about three-four days.

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Marissa

Firstly, I want to thank you for such a wealth of information on tiling!!! We built our 6ftx4ft walk in shower ourselves from the studs up and couldn’t have done it without your instructions. I read dozens of other sites and their “how to” instructions leave out critical steps. We scrupulously followed your instructions for building the shower pan with deck mud and rubber membrane. I also built my curb with your tip of using the stucco mix over the lath which worked great! So now that I have tooted your proverbial horn, please don’t scold me for what I am about to ask. We tiled the shower floor with a carrera (or Chinese similar) polished stone small square tile and used unsanded grout as that gout spaces were small enough to allow. What I have failed to do was seal my tile and grout. I was spreading grout 48 hours before my inlaws arrived and wouldn’t let them shower their 1st day so the grout set for 3 full days. I figured that after a week of showering and hand drying the tiles immediately after that I could seal the tiles and grout after everyone left. Well as life goes for an ADD procrastinator like me….. I still haven’t sealed the tile and it has been being used for 3 months. The grout seems to be receding with use and cleaning or is this just my imagination because I haven’t sealed it? There are no cracks in the grout, but it seems like the grout is too low between the tile. Is there anything I can do other than dig out perfectly good grout to add too it? Is my best option to just seal it now and deal with it?

Reply

Roger

Hi Marissa,

Your best option is likely to just clean it well and seal it now. I honestly don’t know why it would seem to be getting lower after three months, it won’t do that so it may just be the edges of the tiles getting a bit dirty, which enhances the outline of the grout lines – knowwhatImean? If you want to add more grout you’ll need to dig the existing grout down to 2/3 the depth of the tile.

Reply

Leslie

We just had our shower and tile around our tub replaced a month ago by I thought a good company. Well the grout is cracking along the bath tub and I just noticed a vertical line in the shower corner beginning to crack. Also the grout around the shower pan is chipping away. We haven t finished payment yet. What do I need them to do to fix this problem

Reply

Roger

Hi Leslie,

You need to have them remove the grout along the tub (where the tile meets the tub) and in the corners (where one wall meets the other wall) and replace it with silicone. Any change of plane requires a flexible sealant. Silicone can compensate for differential movement in changes of plane, grout will not (which you already know).

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Lisa

Hi! I have a 10 year old travertine shower and it looks like there is caulk over the grout in the corners and the wall to floor. Needless to say, black mold has formed and I cannot get it clean.

I want to redo it, and am willing to do the work to make it right, but I am not sure what to do. Do I sand it out and regrout? Do I caulk over the grout? What type of caulk? Or grout?

Please help!

Reply

Roger

Hi Lisa,

Everything in the corner needs to be removed, caulk and grout, and replaced with 100% silicone. Most grout manufacturers have silicone which matches their grout color, so you should be able to find one that is fairly close to your grout color.

Reply

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