Direct quotes from the by-laws.

A UNIT as hereinafter referred to shall be defined as follows: Each Unit is measured horizontally from the exterior surface of the sheet rock of all opposite walls and vertically from the lower surface of the concrete slab or subfloor forming the lowest floor of the unit to the upper surface of the sheetrock forming the ceiling of the top floor of the unit. Door, windows, interior walls, and electric fixtures which abut a Unit are part of the Unit. The description of the Units set forth herein pertains to the location of the walls, floors, and roof of the Units as they are finally set forth in the site plan and floor plans to be filed simultaneously with the recording of the Declaration.