The spirit of incremental adaptation

Twentieth-century practices in constructing social housing may have been well intentioned, but are ultimately misguided. They do not help to connect the residents to their environment. So much urban fabric all over the world could have been made healthy and sustaining for the same cost, but instead exerts a deadening effect on its residents, and ultimately becomes unsustainable. Unfortunately, government planners were determined to impose an ill-conceived social experiment as part of a utopian program of industrialization. We outline here, on the other hand, practical and sensitive solutions that can be applied immediately to any context, with only minor modifications to fit the local conditions.

The authors make these recommendations based upon considerable experience in practical projects. We will be the first to urge making compromises and needed adaptations in implementing our methodology to any particular project, in the spirit of incremental adaptation. It is far better to compromise and get something built, rather than to insist on following every component of our suggested process but have the project rejected. In this way, we can effect a steady transition to a more robust, more life-supporting, and more sustainable kind of housing for the future. 

Generative Code

 Alexander (2001-2005: Book 3) has applied more advanced “generative codes” to projects, and we summarize here part of his procedure. This is a more incremental version of the “armature of services” layout methodology described previously. 

Alexander observed the self-organizing processes that have created many informal settlements throughout human history, and sought to develop rule-based “generative codes” to exploit these processes. Their natural geometry is so strong that in looking at an aerial view of Querétaro, Mexico, for example (where one of us conducts research), the urban morphology of the informal settlements looks very much like widely admired villages of Provence in France or Tuscany in Italy. They all have subtleties of adaptation to terrain, view, differentiation of commercial functions, and other autopoietic (self-organizing) features. 

The challenge is not to build on a tabula rasa (i.e., by first wiping everything clean) a structure based on a template in advance, but to get plumbing and other humane elements into these already-complex and sophisticated “medieval cities”. We want the organic complexity and adaptive character of “bottom-up” activity, with some of the standards and conditions of social equity that have typically relied on “top-down” interventions. There is a way to lay these out sequentially, iteratively, according to a simple series of rules, as the generative codes propose to do. After that is accomplished, then the result is surveyed and the boundaries are recorded for legal purposes.

It has to be iterative, and determined on-site

A generative layout, including streets, establishes the plots according to topography, existing natural features, and the psychological perception of optimal flow as determined by walking the ground. Then the platting process follows — not the reverse. That would be the Alexandrian approach to “medieval cities with plumbing”. Although it could all occur in advance, as part of a “generative code” process by the community, it just has to be stepwise. Layout should not be template-based or designed to look nice from an airplane. To get the emergent complexity of a living neighborhood, it has to be iterative, and determined on-site. You have to really be sure the organic unfolding can happen, which is not easy in a rigidly codified world. We have the challenge of conjuring good processes out of circumstances that present many constraints and obstacles.

This of course reflects the medieval pattern of laying out streets and lots. It also follows Léon Krier’s dictum that the buildings and social spaces come first, then the streets (Krier, 1998). In medieval cities, the process was highly regulated. A grid-based city can also be well ordered: our point is to use the most adaptive grid for the location, which grows from the terrain. The practical implementation of even a radical generative process is not as difficult as one might think. One gets around the legal problems posed by conventional subdivision law by creating rough “plug” lots that are then laid out in detail according to the generative process; then the plat is made final with a series of lot-line adjustments and right-of-way dedications. There is usually some way to override the conventional processes to achieve this kind of thing, but the government must be supportive and not block the process because it departs from established practice.

Getting into more detail about the layout, the main street has to be laid out approximately based on the topography and connection to the outside. Next, decide on the urban spaces, envisioned as pedestrian nodes of activity connected by streets. Next, side streets that feed the main street are decided — even though streets are still only indicated using stakes in the ground. Next, define the house positions (not yet the lot; just the building) using stakes in the ground, so that the front wall reinforces the urban spaces. 

Each family now decides the total plan of its house so as to enclose a patio and garden in the back. This process is constrained by adjoining streets, alleys, neighbors, and is meant to make the eventual patio and garden spaces as coherent as possible — semi-open spaces that feel comfortable to be in and work in, and not just leftover space. This finally fixes the lot, which is then recorded. Plans are drawn from stakes in the ground.

As lot lines begin to be decided, then the streets can begin to form more definitely in plan (but not yet built). Streets are meant to connect and feed segments of urban space, which themselves are defined by house fronts. (Note that this is the opposite of positioning the houses to follow an existing street). Flexibility in the street design will be retained until houses are actually built. Clearly, you are not going to see many straight streets running across all the development (to the shock of government bureaucrats), because they have not been dawn on the plan at the beginning. Nor do streets need to have a uniform width: they open up to urban spaces. Streets evolve as the whole development evolves. Now begin construction. First build the sidewalks, then the houses, and pave the streets last — if at all.

A more detailed layout sequence will be included in subsequent papers in this series.