As we've written before, building an urban home in Japan comes with two built-in issues: Earthquakes and tight spaces. Muji's latest iteration of their pre-fab home, the Vertical House (which now has a model available for public viewing in Tokyo's Arakawa district), addresses both of these issues via design.
What's interesting, at least to this Westerner's eyes, is the way they went about it. First off, the anti-earthquake joints. Traditional Japanese construction features complicated mortise-and-tenons (below right in the line drawing) where beams meet columns. Under Muji's design (below left in the line drawing) the individual components are beefed up and wooden tongues are replaced with robust hardware designed to maximize strength under seismic loads.
Secondly is the way they've chosen to subdivide the space. Building upwards in a plot with a tiny footprint is a no-brainer, but rather than have contiguous floors, they've opted to first bi-sect the house with an open staircase...
...and then build slightly staggered levels to either side to create six different "zones."
It's like having a succession of differing-height lofts rather than conventional levels or stories. By staggering floors in this manner, each "zone" is distinguished and delineated by the position its floor occupies in space, rather than by potentially claustrophobic walls contained within such a small footprint. (Cultural note: While this wouldn't fly in privacy-obsessed America, consider that traditional homes in Japan are far less likely to invite "company," or non-family members, into their houses; and that the traditional Japanese notion of privacy involves nothing more than a rice-paper-thin sliding door.)
The ceiling heights are calculatedly inconsistent. The mud-room-like open-air entryway, meant to house bicycles or serve as a half-carport, has a low ceiling; so too does the ground-floor laundry room and the kitchen above it, both considered workspaces where an open, airy height is not a priority. In contrast the living room, where family members will relax, has the tallest ceiling in the house at three meters. And as befitting status in a society with Confucian influences, the ceiling height of the master bedroom is slightly higher than the ceiling in the childrens' room.