The Geometry of Community
I was recently consulting with a forming group that's considering rehabbing a school to house an intentional community and they wanted my advice about optimum size and concentration. Although the school has five stories and they were open to the possibility of using the entire space for the community I advised against it—both because it gets proportionately harder to maintain group cohesion as the population increases, and because it gets geometrically harder to establish and maintain group identity as the number of floors increases. I suggested they try to contain the community on three floors.
While creating and sustaining community is mainly a social challenge, that doesn't mean that design and spatial relationships don't have something to say about the outcome.
For example, when community houses are clustered, the people tend to be more involved in each others' lives; when the housing is diffused, so are the social interactions (think about the relative isolation of people who live in the suburban sprawl of one house per acre—where you have to put on sun block in order to borrow a cup of sugar). If the houses are laid out in a circle, the differences are less pronounced. When the housing is strung out in a line, the end folks are simply not in the social flow as much as others and that affects relationships. If there's a common house and that's the epicenter of community action, then the key is how close a given house is from the common house—even if the common house is on the edge of the community.
To be clear, location is not destiny. It also makes a difference how much you hang out on your porch, attend potlucks, throw card parties, and/or have a reputation as a grouch who eats small children. In short, behavior is also a big factor. With a nod in that direction, today I want to focus on the predictable challenges associated with different physical layouts.
The Vertical Challenge
In addition to how closely a home is located from the center of activity, multistory communities have an additional challenge in that different floors tend to be completely out of sight of one another. At least with a strung out community you can see the house at the end of the row; it's damn hard to see the apartment above you. (Hint: being able to hear the couple above you argue or make love does not necessarily count as a bonding experience.)
Regardless of whether we're talking about people being spread out or stacked up, the key thing is promoting flow by one another's units. If there are public reasons that will bring people by where others lives it promotes informal social contact, which is the main lubricant of community. In the case of vertical communities (high-rises built on a small urban footprint), the question is how to locate functions such that most residents will need or want to travel to all floors.
This means public functions commingled with private ones. Maybe there's a pedestrian entrance on a different level than the parking entrance. Maybe you can have an exercise facility or entertainment room on different floors; maybe there's meeting space or a craft center on different floors than the entrance. The kitchen/dining room could be on another floor still. How about the mail room and community bulletin board, or the little kids' rumpus room?
While it's often convenient to clump public functions together (one stop shopping) that strategy may have the unintended consequence of promoting private space ghettos that no one ever visits unless they're going there on purpose. While no doubt some inter-visitation will happen no matter what you do (you can, after all, reasonably count on some degree of spontaneously occurring social interplay among residents), community depends on flow.
How will you draw people into walking by the units at the end of the hall on the top floor? How will you attract residents into going by the house built furthest from the common house (Hint: locating the dumpster there is a weak solution—while it guarantees traffic, who wants to hang out by the garbage)?
While everyone enjoys some moments of privacy and quiet, you do not want to design your community such that the housing reinforces people being isolated. There's more than enough of that in the mainstream culture already.