The mezzanine area shall include any structure over thirty (30) inches above the floor and shall not exceed one-third of the floor area of the live/work room in which it is placed. If an area is classified as a mezzanine, the wall separating the room and the mezzanine shall be at least fifty (50) percent open. If walls are less than fifty (50) percent open the area above shall be classified as a story. (Prior code § 9.29.1310)