07:47PM | 06/23/02
Member Since: 06/22/02
4 lifetime posts
Help! We moved into a new home 1 1/2 yrs ago. About one month later we noticed hairline cracks in the grout of our ceramic tile floors. This includes a large area of our home. The Tile was installed over 3/4 inch subfloor and 3/8ths inch plywood which was either nailed or screwed to the plywood. The installer has been back 3 or 4 times to fill the cracks by regrouting. Most have re cracked. We are not having a problem with cracked tiles, and the floor seems sound. Is this a problem w our subfloor? Is it poor quality grout? Was it b/c the floor was installed in the winter? Was it b/c the tile was installed 5 weeks b/4 it was grouted? Any insight would be appreciated. Thanks.


09:41AM | 06/24/02
Member Since: 03/13/00
1675 lifetime posts
An "expert" should answer this, but I've learned (partly from this forum) that if the area is "larger than a breadbox", you should put down concrete board under ceramic tile to prevent the slightest flexing of the plywood floor. If there is any flex at all when a heavy person walks on the floor, the grout will crack.
Sounds to me like the contractor may not have done the job right.


05:17PM | 06/24/02
When the grout was mixed do you know if water was used or did they use an acrylic or latex additive in place of the water? It is a milky looking liquid that when used in place of water when mixing the grout it will help the grout stick better, make it more flexible, and will help water proof it. If this was not used then try removing the cracked grout with a grout saw and replace it with some that has the acrylic-bonding additive in it. It may solve your problem.

If this does not help the only solution may be to redo the entire floor, tile and all. Use a product called “Hardibacker” screwed into the floor joists using the special screws made for this application. This is a ¼” thick cement and fiber based product made for use under ceramic tile. Be sure to stagger the seams. (Check the floor very carefully first to make certain there are no weak spots that are deflecting (even the slightest bit) when walked on. If you find any they must be repaired first either by cutting them out and replacing them or by adding additional blocking underneath. The sub floor MUST BE devoid of any soft areas prone to deflection.

Good luck and I hope you do not have to re-do the entire floor.



06:24PM | 06/24/02
Member Since: 06/22/02
4 lifetime posts
Hi. Thanks for your response. The installer left the bag of grout here. It is Custom Polyblend. The package instructions say to use water and not to use additives. So I am guessing that just water was used. I too hope we will not need to replace the floor although removing all the cracked grout sounds just as laborious.
Also, the cracks run along the grout were it meets the tile-dont know if that makes a difference in your opinion. Also have discovered that the plywood was stapled to the subfloor (dont know if nails were used at the joists). Let me know if any of this affects your opinion. Thanks again for all your help.


03:24PM | 08/29/02
Member Since: 08/28/02
1 lifetime posts
Two years ago I installed approx 400 sq ft of ceramic floor tile. Cracks have appeared in 150 sq ft of the total area, and located in the area of the first bag of grout. The grout was a polyblend and came with the direction to use only water for mixing. Since I removed the builders installation of ceramics as part of the project and they didn't have any cracks,I am sure that the problem isn't movement in the subfloor. I also added 3/8" plywood over the existing 5/8" plywood before installing the mesh and thinset base. After many hours of guessing and blaming the first bag of grout as being defective I realized that the problem may be of my own doing. In an effort to rush the job along I did not wait the recommended 15 minutes before using the mixed grout. I thought why should it wait in the bucket when it can wait on the floor. Well, since the other 250 sq ft of floor hasn't cracked and I did wait the recommended time after mixing,I am quite sure that the problem was the grout didn't develop the necessary properties, or whatever it does in that 15 minutes. My problem now is that I need a good method of removing the grout without using the basic grout saw, which will take weeks to do. Any advice is appreciated.


04:27PM | 09/13/02
Member Since: 09/11/02
2 lifetime posts
From what you wrote it could be several things 1)check the tiles to see if tiles are down good simply tap each tile with the back of a screwdriver do they all make the same sound or do some sound hollow if they do replace those tiles and grout. 2) you may have a heat or cold source running under the floor at that spot creating undo expantion and contraction. 3) you may have a high crown joist at that spot check from the under side if possible by running a string tight on bottom of all joist and last (the one I would bet it is) 4) once the floor has been properly grouted are you misting it with water every 12 hours for a 72 hour period to retard the grout from drying to quickly and cracking. (I have seen this be the problem on 9 out of 10 grout cracking prblems where no tile are cracking)
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