December 2018 - last edited December 2018
@HugoBellucci I have not ever made a curved floor and wasn't aware this could be done (is this a mod? ...if not, I would love to know how you do it), but I have found that there are areas of the building that will not let me add certain trims. I have found this is the case with friezes, exterior trims and even sometimes spandrels in my builds. So, sometimes I am not able to use a trim I would like on a building because it will not apply to all of the areas that I want it to. If this is the case, it is possible that this curved area is one of those types of areas.
My typical solution is that I test what will work and if it will work in all areas I need it to be consistent for the design. Then I typically modify what I end up adding to fit what the game is willing to 'trim' in the way I want. Occasionally I do find that if I modify the area the trim will work then. This can include design modification, checking if there is a remnant you were not aware of of a previous wall/roof/etc. 'designated area' in the builder even though the wall/roof/etc. was deleted. Sometimes re-tracing (with the wall tool) that area's wall or re-tracing the area above, moving a wall to where the trim will go to then back to where it was, etc. can correct this and the trim will then work, etc. A bit of a dance. Frustrating. Very.