(a) The respective occupants of lands enclosed by fences shall maintain partition fences between them in equal shares, as long as both parties continue to improve the same.
(b) Where any person encloses land adjoining another's enclosed land, so that any part of the fence, or fence and ditch, or hedge and ditch, or wall, already made, becomes a partition fence, the fence-viewers shall determine what sum shall be paid by the one to the other, and the fence shall then be maintained by the parties equally.