No hospital, school, church, college building, nursing home, rest home, convalescent home, library, museum, and community center or public recreational building shall be closer to any street line than 50 feet. Every principal building shall be on a lot with a minimum width of 150 feet at the street line and a minimum area of 1.5 acres. Every principal building shall be provided with two side yards totaling 50 feet in width, the minimum width of any side yard being no less than 20 feet.