Our small coop has a brick retaining wall that divides our garden from the neighbors garden. We are in the process of analyzing an updated property survey, but it seems that the wall sits on our property, with the edge exactly on the boundary of our neighbor's property line. There are essentially two layers of brick, which are almost like two walls. The owner of the garden floor apartment has exclusive access to the garden, and is paying to repoint and replace the damage brick accessible from their property. However, the other side of the wall also needs repairs.

Who is responsible for fixing the other side of the wall? The neighbor - who has access and use as a property line divider? The coop - who owns the underlying property? The unit owner - who has sole access?