Front yard. The uniform setback provisions of § 470-3.03B shall apply to all residential buildings, structures, and additions. If a uniform setback does not exist, the front yard setback shall be not less than 40 feet, except that when adjacent to a primary street, the front yard setback shall be not less than 50 feet, and when adjacent to a major arterial street, the front yard setback shall be not less than 60 feet.