Party Walls
/Do you have a wall on the boundary?
What is a party wall? The term this is a wall normally in a terrace house or the like, that you and your neighbour share. Shown Below
A wall on the boundary. If your next-door neighbour has a shed on the boundary instead of a fence this in not a boundary wall that you can build off. It belongs to the neighbour and their building. If they removed the building your building would still be standing not attached to it. There may be a small gap.