Except as provided by the declaration:
(a) 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.
(b) If any chute, flue, duct, wire, conduit, bearing wall, bearing column, or any other fixture lies partially within and partially outside the designated boundaries of a unit, any portion thereof serving only that unit is a limited common element allocated solely to that unit, and any portion thereof serving more than 1 unit or any portion of the common elements is a part of the common elements.
(c) Subject to subsection (b) of this section, all spaces, interior partitions, and other fixtures and improvements within the boundaries of a unit are a part of the unit.
(d) Any shutters, awnings, window boxes, doorsteps, stoops, porches, balconies, patios, and all exterior doors and windows or other fixtures designed to serve a single unit, but located outside the unit’s boundaries, are limited common elements allocated exclusively to that unit.