Did you scrape off all the old thin set?
What condition is the plywood in?
Not sure what you mean by "backer board", should be laying subfloor rated plywood and filling any gaps and flaws so you have a flat surface.
Pictures are your friend here.
What condition is the plywood in?
Not sure what you mean by "backer board", should be laying subfloor rated plywood and filling any gaps and flaws so you have a flat surface.
Pictures are your friend here.