GROUT [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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08-18-2001, 09:14 AM
This is a REAL simple question (I think)......
Installed 4x4 tiles, grouted and cleaned and the floor looks great...except...for one area around one tile where the grout has chipped away. SO.....grouted that area again ,and the grout continues to fall out. The new grout didn't "stick" to the old. SHould I have wet the original grout before grouting over, or what could I do to make the two adhere to each other?
Thanks in advance for any advice.

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Rob Z
08-18-2001, 10:57 AM
Hi James

The grout could continue to break apart if that one tile wasn't set well-if the tile is loose, it moves as the floor is walked on and stresses the grout.

What did you use for underlayment, setting material, and grout?

Does this tile sound hollow when you tap on it with a piece of wood?

Let's get the answers to these questions before you try to keep pushing grout into the joints around this tile.


John Bridge
08-18-2001, 11:51 AM
Yes, it sounds like a loose tile. Break it out and replace it. Grout will never hold if you don't.

08-18-2001, 12:01 PM
The tile is absolutely in there solid. I used a Wonderboard underlayment and (not sure of the name) but a heavy-duty mastic (recommended by the tile store). Just checked the tile and it doesn't budge a bit. Not sure why the grout came out but still think the problem is that it is not "bonding" withthe original grout that is still there.

Rob Z
08-18-2001, 12:14 PM
Hi James

"Mastic" and "heavy duty" are two terms in the tile business that are mutually exclusive, notwithstanding what your tile store may have told you. I have seen cases where the mastic used to set a tile was still rubbery months later, because it was unable to cure for some reason.

Grout will grab onto, or bond, to old grout of the same formulation with no problem, so I think that the problem is one of two things:

1. The mastic has not cured underneath this tile, and the moisture coming off the mastic is causing problems for the grout (this is less likely the longer the tile has been down).


2. The tile is loose, even though you don't detect it by pushing on it with your hand. Small joints filled with unsanded grout are very weak, and the slightest movement can cause the grout to crack.

How long has it been since the tile were set?


John Bridge
08-18-2001, 12:57 PM

If I were to try to bond old grout to new, I would dampen the old grout. But I still agree with Rob.

Rob Z
08-18-2001, 01:02 PM
Hi James

Yes, dampening the grout helps the two applications bond to each other. Dampen it will a sponge-no standing water in the joint or on the tile.


08-18-2001, 01:57 PM
If you grouted within a day of installation this may very well be a case of fighting against the natural curing process of the Mastic...which is longer than thinset.

If the joints are small,say 1/16", use a stanley-knife and scratch out "ALL" the grout aroung that tile.Be sure there is plenty of mastic under it and it is adhered soundly.If so,leave the grout out for a couple days.This will give the mastic time to set up adequately.Regrout after that and it "should" be fine.

P.S.James,mix your grout a little dry.You should have to "pack" it into the joint.This will help with the curing time and will all but eliminate shrinking which can cause the grout to "pull" away from the tile and/or crack.

[Edited by kalford on 08-18-2001 at 07:39 PM]

08-20-2001, 05:15 AM
Potential solution # 3, is that an area under the cement backer board may have not been properly filled with a leveling bed of mortar to fill a void. That void may be under this one problematic tile.

It is possible that this one tile is compressing into the unfilled void and causing your continued problem.

To test for this, have some one step onto the tile while you watch for movement.

What did you use under the board?


08-20-2001, 04:59 PM
Really appreciate all the advice...though still not convinced the tile is loose. Will try to dampen the remaining grout, pack the new grout in dry-ish and see if that works. If not, then I'll believe it's loose and pry it out and start all over.
Really cool to have this resource.....I'm thinking of new tile in the kitchen so I'm sure I'll need advice again.