Rear yards. Where a West End Business WEB District adjoins a residential district at the rear, rear yard requirements shall be as follows: There shall be a rear yard of not less than 40 feet deep. Otherwise, the rear yard requirements shall be as follows: There shall be a rear yard of at least 20 feet in depth, except that if the building is used for dwelling purposes other than by one person acting as a janitor or caretaker, the rear yard shall be 30 feet deep. For a building that extends through from street to street, front yard requirements shall apply on each frontage.