Possible Water Damage To Floor?

Q: I recently had 20” x 20” porcelain tiles installed in my kitchen – tiles were installed on top of an old raised wood subfloor and then used a 1/4” hardibacker board and then thin-set. Floor was fine for about 5 months but recently, some tiles have loosened to the point that I was able to remove three pieces without breaking them. To my surprise, there was no thin-set adhered to the back of the tiles. There was however some cracks in the thin-set on the floor. Here is where things get tricky. Prior to any tiles loosening up, we had a flood in the basement below the kitchen. Could several days of moisture in the basement cause the wood subfloor to warp and move, then causing the thin-set to crack, and finally loosening my tiles? The flooding continued for two more rains before we found the cause – new hole for water pipe made by my contractor.
In your professional opinion, is my tile floor coming apart because of a poor installation or was it caused by the moisture in the basement?
Thank you.
Best,
Ryan T.
A: Based on your description my guess here is that this is the fault of the installation. When tiles come up without mortar attached to them, then there is one of several things happening which all point back to installation and the setting material. Using the wrong setting material, insufficient amounts of setting material, or the wrong trowel are all good examples of what causes the problem you are encountering.
I had a quick conversation with Gene D., iFLOOR’s commercial contract specialist, who noted that to his experience that with a 3/4″ subfloor on 16″ joists should be using a 1/2″ hardibacker board, not 1/4″, which runs at a 90 degree angle to the plywood subfloor.
Now if this was related to the flooding you had, then the loose tiles would have had some mortar still attached to them, as this would show the mortar set properly and adhered to the tiles across the entire floor. This would be evidence of the subfloor expanding and cracking/loosing the mortar and tile.