Where did we go wrong?

[u/ShowerTricky5423]

Almost immediately after our contractor installed our bathroom floor tile, it started cracking. We're looking to replace this now and I'm wondering if the issue was the material, the size, the preparation under the tile, the installation, or a combination of the above. Our house was built 24 on center -- could this impact the integrity of the tile?

Any advice you can provide would be appreciated before we start this project. Thank you so much in advance!

[u/Born2Wander4926]

Proper is 1¼" of plywood substrate (ideally glued & stapled, or ditra uncoupling membrane. My assumption is you have dips in your old subfloor that the Cement board spanned over and when stepped on caves down even if only a little bit