[QUOTE=CaveMike]
I just moved from a 4-level as you described in your diagram and I am intrigued by the idea that it minimize’s hallway/stairway space, but I am having trouble picturing it. Refering to your drawing, it seems that you could shift the two left levels up 1/2 a level, keep the stairways as switch-backs, and still maintain the existing layout (at least in my old house). You would lose some of the openness that you get with 1/2 stairways.
I always assumed that most splits were just designed for aesthetics. The floor plan can be a little bit more open. In the case of 4-levels, it seems like the basement and sub-basement would be a pain to excavate and pour, but that is probably just my naivete.
And as has already been stated, you never have to climb more than a half-flight of stairs, but you always have to climb a half-flight of stairs.
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In our split, the stairs to the 3rd level went straight down into the family room, so there were no hallways on that level at all (a bedroom door at the back of the family room). On the top level, the stairs opened onto a small foyer that had a two doors in the middle of the wall for the wide bedroom, a door at one end for the master, and a door at the other for the bathroom. Total hallway space in the entire house - about 6 ft.
You CAN accomplish almost the same thing in a 2-story, but it’s hard to do. As you said, you could have a stairwell with a landing halfway up that switched back in the other direction, but if it lands at one end of the much larger floor, you have to have a long hallway through the top level. If you land it in the middle, you can have the rooms clustered around it in a circle and save hallway space, but then your stairwell sits smack in the middle of your main floor, breaking up the space.
So if you want an open floor plan, it can be hard to do with a 2 story in a space efficient manner. For example, our current house is a 2 storey, and it’s VERY open on the top two levels, but it’s that way because the top level is half missing - the main level has a living room that opens up 2 stories, there’s a curved stairwell going up to an open landing, and then bedrooms are at each end of a walkway that cuts across the house. The result is an upper level that’s only 1100 sq feet, even though the main level is almost 1600. And about 100 of that square footage on top is hallway and landing.
There are advantages and disadvantages to all these designs. It’s easy to get an open floor plan with a split. And I’m guessing that structurally a split is very simple, because you’ve got that center load bearing wall going right through the entire middle of the house.
Another design that’s common around here is the ‘front to back’ split, and these are especially efficient on long, narrow lots that are common in the city. By running your levels front to back, you can pack a lot of house onto a narrow lot. A 2-story of those dimensions would be strange with the narrow and long levels. With the front-to-back split, each level is still relatively square.