Posted:
There are always exceptions, as JeanneK3 posted, and also possible variations between the States.
The Condominium Units that I am familiar with, define the uppermost ceiling as the upper horizontal Unit boundary - something like: (excerpts, definitions, taken from the 2008 UCIOA, so as to be general)
SECTION 2-102. UNIT BOUNDARIES. 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.
And the comment below, from the UCIOA, speaks to the question asked by JerryD2, if in fact the Attic in question is defined as Common.
“3. The differentiation between components constituting common elements and components which are part of the unit is particularly important in light of Section 3-107(a), which (subject to the exceptions therein mentioned) makes THE ASSOCIATION RESPONSIBLE FOR THE UPKEEP OF THE COMMON ELEMENTS and each unit owner individually responsible for upkeep of his unit.”