Except as provided by the declaration:
(1) If walls, floors or ceilings are designated as boundaries of a unit, all lath, furring, wallboard, plasterboard, plaster, paneling, tiles, wallpaper, paint, finished flooring and any other materials constituting any part of the finished surfaces thereof are a part of the unit, and all other portions of the walls, floors or ceilings are a part of the common elements.