53 Pa. Stat. § 24873
The said party wall shall be erected by the party first building at his own cost, including the cost of survey, plans and specifications herein required, and when fully completed the cost of the same shall be ascertained by the said superintendent, or his agent, who shall, at the same time, determine the proportion thereof to be paid by the adjoining owner, of which he shall give a certificate to the builder, which certificate shall be conclusive of all matters therein contained: Provided, That at least forty-eight hours' notice shall be given by said superintendent or his agent to the owner or owners or occupant of said adjoining lot before said certificate shall be given to the builder of the time and place when he may be heard with reference to the same. The owner or owners of said adjoining lot, his or their heirs, assigns or lessees, shall not use said party wall by building into or against it, or by in any way using it for any new building or structure, until he or they shall have paid to the first builder or builders, his heirs or assigns, the proportion of the cost of said wall as fixed by said superintendent or his agent, or of so much of it as he may desire to use.
53 P.S. § 24873