I installed 1800 sf of 1/2" Hardie backer, I first used self leveler in many area's to eliminate uneven surfaces. I then screwed the backer board down every six inches over the self leveler and 3/4" plywood. I was unable to put thinset down because it would have prohibited me from opening entrance doors throughout the house (the tile was thicker 5/16 of an inch). I have been told that the tile or the grout joints will crack. I also installed expansion joints at numerous locations. What is your take on this?

Thank you

If by "screwed the backer board down every six inches " you mean around the perimeter and in the field, you should be just fine. Main thing is the stiffness or rigidity of the floor.

I am curious thought, why can't you trim doors slightly?

If by "screwed the backer board down every six inches " you mean around the perimeter and in the field, you should be just fine. Main thing is the stiffness or rigidity of the floor.

I am curious thought, why can't you trim doors slightly?

The doors are fiberglass and steel.