An article pointed by MSN discussed a new trend in apt buildings. Most US codes require two stairways, for fire access among other things. Supposedly fire prevention is so good now that we can build cheaper with only one stairway. First, that’s nonsense. Second, the other things are important.
Here’s my floor plan of Grandma’s apt in Ponca, with separate front and back halls separated by a wall.
The back hall (mystery hall) made it possible for residents or service workers to get in and out without bothering people in the front hall or the living room. With only one entrance, everyone has to pass through the same common space, which may be unsafe or unsavory for all sorts of reasons.
In the ’80s I lived in a crappy basement apt in Pennsylvania, with access only from an open gallery on the front. When the landlord decided to do construction work on the front gallery there was no way out. I had to climb through a window to get to work.
Polistra's Mill 