We have a rent house that the shed was built on to the house but is not accessible from within the house. The shed uses the back wall of the house as a wall for the shed. They are not under the same roof.

Is this considered a separate building or considered part of the home like a regular garage under the same roof would be?

Single Building: A building that is separated from other buildings by intervening clear space or solid, vertical, load-bearing division walls.

In other words, it is attached and not a separate building.