68 Pa.C.S. § 5202: Unit boundaries.

Except as provided by the declaration:

(1) Subject to the provisions of paragraph (2), all space, fixtures and improvements within the boundaries of a unit are a part of the unit.

(2) If any fixture or improvement lies partially within and partially outside the designated boundaries of a unit, any portion of the fixture or improvement serving only that unit is a limited common element allocated solely to that unit, and any portion of the fixture or improvement serving more than one unit or any portion of the common facilities is a part of the common elements.

(3) Any fixtures or improvements designed or designated in the declaration to serve a single unit, but located outside the unit's boundaries, are limited common elements allocated exclusively to that unit.