Doors shall have a clear opening of no less than thirty-two (32) inches when fully open and shall be operable by a single effort. The floor on the inside and outside of each doorway shall be level for a distance of five (5) feet from the door in the direction the door swings and shall extend one (1) foot beyond each side of the door. Sharp inclines and abrupt changes in level shall be avoided at doorsills. As much as practicable, thresholds shall be flush with the floor.