We also have a boundary like that (although we are a terrace and the houses connect over the passageway) - our house 'owns' the passageway and we are solely responsible for maintenance; neighbours have access rights (although in practice never use them). All made explicit in the deeds.
We also have a boundary like that (although we are a terrace and the houses connect over the passageway) - our house 'owns' the passageway and we are solely responsible for maintenance; neighbours have access rights (although in practice never use them). All made explicit in the deeds.