Texas Property Code - PROP § 81.105. Apartment Boundaries

(a) The boundaries of an apartment in a condominium regime are the interior surfaces of the apartment's perimeter walls, floors, and ceilings, and the exterior surfaces of the apartment's balconies and terraces.

(b) Except for common elements, the portions of a building on the boundaries of an apartment in a condominium regime and the airspace within those boundaries are part of the apartment.

(c) In interpreting a legal instrument relating to an apartment or to an apartment that has been reconstructed substantially according to the original plans of the apartment, the physical boundaries of the apartment are conclusively presumed to be the proper boundaries of the apartment regardless of settling, rising, or lateral movement of the building containing the apartment and regardless of variances between boundaries shown on the plat of the building and the actual boundaries of the building.