in order to use joined floors I need to make sure that the top one never extends beyond the bottom one. To explain the situation: When you cast a concrete floor for a sloped parking basement, you first cast a sloped floor that has no sideways sloping, but only one general slope. On top of this structural floor you then cast a leveling concrete floor that has sideways angles as required for water draining and cleaning. What you suggest is possible but requires complicated calculations of the intersections between the two floors. I was looking for a shorter, wiser way of doing that. If you can think of any I'd be grateful. I was not able to that. I do have an app, the Environment app that allows for dropping one floor on top of another, or sticking it underneath. However, that makes the two floors the same. That is not what I need. I attach an explanatory sketch.
Thanks for your efforts.