Preventing cracking tile

QUESTION

A family contacted me to put new tile in their kitchen. Tile was installed about seven years ago and it’s cracking and coming loose. I attached some photos to see if they give a clue to what may have caused this failure. It appears it’s installed on cement board; the tile has crack lines about every 4′ to 5′, then areas where it’s all crumbled up. It appears it has hardly any thinset.

ANSWER

Thanks for reaching out to the NTCA Technical Team. I’ve taken a look at the photos you sent, and it appears there are a few factors contributing to the issues with the tile installation:

1. Lack of thinset: It seems there might be insufficient thinset. The TCNA Handbook methods and ANSI standards require 80% coverage in a dry area and 95% coverage in a wet area.
2. Improper cement board installation: The crack lines you mentioned occurring every 4′ to 5′ could indicate movement or improper installation of the cement board. The cement board should be placed in a bed of thinset, secured properly with the right screws and screw spacing. Each 3’x5′ board should have a slight gap between them, and all joints should be taped with alkaline-resistant mesh tape (Follow the manufacturer’s instructions). I do find it interesting that you stated there are cracks in the tile every 4′ to 5′ when a piece of cement board is 3’x5′. 
3. Tiles installed with no grout joint: All tiles, including stone travertine with a beveled edge, require a grout joint. The minimum grout joint for all tile and stone installations is 1/16″. This does not appear to be the case in the pictures you sent.
4. Substrate deflection: The tile in your photos appears to be travertine stone. All stone installations require the subfloor to have a deflection rating of L/720. This may be hard to determine even after the floor has been removed, but generally, a wooden subfloor with a single layer of plywood will not meet this deflection rating. Please see method F250 Stone on page 366 in your 2024 TCNA Handbook for an example of how to properly install stone over a wood subfloor.

Please note that we are not inspectors, and there is no way for us to know exactly what happened without being there in person and only seeing pictures. If you need further assistance assessing the problems, we recommend contacting a recognized tile consultant who can be found on our website www.tile-assn.com. Let me know if you need any further assistance.  

Ask the Experts Q&As are culled from member inquiries to NTCA’s Technical Team. To become a member and make use of personal, targeted answers from NTCA’s Technical Team to your installation questions, contact Jim Olson at [email protected].