53 Pa. Stat. § 24871
Any person or persons who may be now erecting or may desire hereafter to erect any house or building in such cities, and who may desire to erect therewith a party wall to be used in common by the person or persons erecting, and the owner or owners of the adjoining lot may apply to the said bureau of building inspection of such cities signifying his or their intention to erect a party wall, and describing the location of his or their lot and the lot adjoining, partly upon which said party wall is to be erected, with the plans and specifications of the said proposed wall and the materials of which the same is to be built, whereupon it shall be the duty of the said bureau of building inspection to appoint a time at which the superintendent thereof, or some person by him authorized, will meet the party or parties upon the premises, not more than five days thereafter, of which application a copy, with notice of the time so appointed, shall be served by the said bureau of building inspection upon the occupant of said lot at least three days before the time so fixed. If said lot is unoccupied the said notice shall be served upon the owner or one of the owners of the same, if he reside within the county in which such city is situate, at least forty-eight hours before the time fixed. Service thereof may be made either personally or by leaving a copy of the notice at the residence of the owner or occupant. If there be no owner or occupant resident in the said county, or if such owner be unknown, such notice shall be posted upon the premises and shall be equivalent to a service.
53 P.S. § 24871