The bathroom in a Rogers Park courtyard building is usually five by seven, off a central hall, with a cast-iron tub in an alcove, a pedestal basin and often no window. It was built in about 1925 and in a great many flats it has never been taken back to the studs.
Two things are settled before design starts. The waste riser is shared, so the toilet stays close to the branch that reaches it. And the floor is shallow, which limits how far a new drain can travel at a proper fall.
Neither stops the room being transformed. The tub nobody uses becomes a level-access shower, the pedestal basin becomes a vanity with real storage, and the fan finally goes to outside air instead of into a shaft. That is the project here, and it is a smaller job than most people assume.