Buildings are separated by a double line.
The second, and more, schedules (families) in the same building are separated by a single line.

Uninhabited buildings appear between two schedules - if it is uninhabited there can't be any names associated with it.

You'll come across many cases of unihabited buildings noted (as here) apparnetly in the middle of a schedule.

Hope that is clearer than the mud it sounds like.