Basement Bathroom Floor Finish height – GreenBuildingAdvisor

We’re in the process of putting a bathroom in our completely unfinished basement.  Concrete slab is old (no poly) but in good condition of our 1920s house in Minneapolis.  I’m struggling to determine the right way to dial in floor heights.  We currently have the floor trenched for drainage/sewer plumbing.

For the bathroom, I’m planning the following build:  Slab – thinset – Cerazorb (thermal break – 6mm) – thinset – Ditra Heat (6mm) – thinset – quarry tile (12mm).  Total stack is ~1 3/8″

I’m considering three options:

A.  Start basement floor from current slab level, have a 1 3/8″ floor difference to account for at bathroom threshold.  Pro:  Easy to complete. Con:  This seems like too much to transition well.  

B.  Break up the rest of the concrete bathroom and pour new concrete to be below the rest of the basement.  Pro: No transition at threshold.  Cons: more digging, can’t finish basement floor at a later date.

C.  Plan for a finished floor in the rest of the basement (foam and double layer of plywood floated = 2″) and build bathroom floor to match.  Pro: Easy to match transitions.  Con: More cost, did not have plans to finish basement floor.

There are some other options to consider:  use a thinner floor tile, Use SLC to bring up the rest of the basement floor (or at least max at bathroom and sloping away).

I want to lean to C, just because it covers all the bases.  However, we had not planned to finish our basement floors, so adding that into our bathroom project is hard to grasp, but might be the right choice.