Side yard: 40 feet, except that where two or more property owners propose to erect abutting office structures which are developed and maintained as a unit, the Planning Board may waive the side yard requirements between buildings, provided that the uninterrupted length of any one building shall not exceed 200 feet in length, and provided that the Planning Board will have appropriate assurance that the office complex will provide harmonious and unified exterior facades on all sides. In no case shall there be less than a total of 80 feet of side yards nor less than 30 feet in any one side yard for any one structure.