53 Pa. Stat. § 14839
In tenement-houses, lodging-houses, factories, workshops, and all public buildings, the entire water-closet apartment and side walls, to a height of sixteen inches from the floor, except at the door, must be made water-proof with asphalt, cement, tile, or other water-proof material, as approved by the Board or Bureau of Health. In tenement-houses and lodging-houses, the water-closet and urinal apartments must have a window or windows opening into the outer air, of sufficient size, all of which shall be shown on plans, and shall be subject to the approval of the Board or Bureau of Health. Except that tenement or lodging-houses, three stories or less in height, may have such window opening on a ventilating-shaft, not less than ten feet square in area. In all buildings, the outer partition of such apartments must extend to the ceiling, or be independently ceiled over, and these partitions must be air-tight. The outside partitions must include a window opening to outer air on the lot whereon the building is situated; or some other approved means of ventilation must be provided. When necessary to properly light such apartments, the upper part of the partitions must be of glass. The interior partitions of such apartments must be dwarft partitions.
53 P.S. § 14839