53 Pa. Stat. § 24872
At the time appointed, the superintendent of the said bureau, or some suitable person by him appointed, shall have the line dividing said lot properly surveyed by the bureau of engineering and surveys of such city, and the land upon which the said party wall is to be erected, with the breadth and length of the same, and which wall shall be equally one-half upon the land of each of the adjoining owners, unless the adjoining owners shall object that said wall as proposed is thicker than necessary for the purpose of any ordinary building. If such objection shall be made, then the said superintendent, or the person by him appointed, shall determine how much of said wall shall be placed upon each of said lots, and shall decide the same within forty-eight hours after the said objection has been made, and his decision shall be final and conclusive upon all parties.
53 P.S. § 24872