How to tile a ceiling in a slanted shower?

[KBEDesign]

I am working on a bathroom rendering that has a sloped shower in which the ceiling will be tiled. In order to create the slope, I used a ceiling plane. When I tile it, it tiles the whole plane instead of just the shower section. Is there a way to specify where you want the material, similar to wall/floor material region but on the ceiling? Pic for reference.

[robdyck]

You could use a separate ceiling plane just for the tile finish or use a 3d solid.

[PitMan71]

Create a room for the shower and change the ceiling finish.