Stewart Brand’s How Buildings Learn is one of my favourite books, maybe one of the half dozen non-fiction works I would take to a desert island. It’s a book about buildings, and specifically how buildings are modified and adapted over time, but the theoretical ideas on which it’s grounded can be applied to any type of system.

The argument is illustrated by sequences of photographs, and these are the greatest asset of the book. Brand has trawled the archives for sequences of photographs of the same building or street scene taken at different times. The cover features two Greek Revival townhouses on St. Charles Street in New Orleans; identical in a auctioneers drawing made in 1857, quite different in a 1993 photograph after various modifications to add storeys, extensions, balconies, windows and entrances.

The theoretical grounding is based on the insight that that while many buildings are designed and managed as spatial wholes, none are designed and managed as temporal wholes, and there are very few theorists of building through time. The underlying idea is expressed by British designer Frank Duffy.

‘“Our basic argument is that there isn’t such a thing as a building. A building properly conceived is several layers of longevity of built components. The unit of analysis for us isn’t the building; it’s the use of the building through time.”’

Brand argues that the founding idea of modernism, that ‘form ever follows function’, articulated by high-rise architect Louis Sullivan in 1896, has misled architects into thinking they can anticipate function. Instead he proposes that function melts form; that as buildings are adapted over time to suit the needs of the occupants, form undergoes continuous modification.

Duffy originally distinguished four layers of longevity: shell, services, scenery and set. Brand extends and generalises this schema into six layers. Site is the location, the geographical setting and legally defined plot. Structure is the foundations and the load bearing components. Skin is the exterior surfaces, the weatherproofing. Services are the cables, plumbing and conduits which provide communications, monitoring, heating, ventilation, air conditioning and so on. The space plan is the interior layout, partitioning and circulation. And stuff is the furniture and appliances, the mobilia.

Each layer operates to a different timescale. The setting is more or less permanent. The structure should last 60 years, but maybe several centuries. The exterior surfaces need to be replaced every 30 years, the services probably become outdated in 15, the partitioning is changed maybe every few years, and the stuff is constantly being moved around and replaced.

The design process and the construction process both follow this sequence. The layering also defines how the building relates to people. The individual is concerned about the furnishings, the tenant about the space plan, the owner about the services; the public about the exterior surface, and the community about footprint and usage of the site.

Similar ideas can be applied to ecosystems. Brand quotes Robert O’Neill and his co-author’s  A Hierarchical Concept of Ecosystems to suggest that eco-systems can be better understood by observing the rates of change of different components.

‘Hummingbirds and flowers are quick, redwood trees slow, and whole redwood forests even slower. Most interaction is within the same pace level – hummingbirds and flowers pay attention to each other, oblivious to redwoods, who are oblivious to them. Meanwhile the forest is attentive to climate change, but not to the hasty fate of single trees. The insight is this: “The dynamics of the system will be dominated by the slow components, with the rapid components simply following along”. Slow constrains quick; slow controls quick.’

Although not entirely. The longevity of building is often determined by how well they can absorb new services technology. Brand’s book is about how building can be built to adapt.

‘An adaptive building has to allow slippage between the differently paced systems of Site, Structure, Skin, Services, Space Plan and Stuff. Otherwise the slow systems block the flow of the quick ones, and the quick ones tear up the slow ones within their constant change.’

He also quotes professor of architecture Chris Alexander, who’s thinking about what makes buildings humane is inspired by how design occurs in nature.

‘“Things that are good have a certain kind of structure” he told me. “You can’t get that structure except dynamically. Period. In nature you’ve got very-small-feedback-loop adaption going on, which is why things get to be harmonious. That’s why they have the qualities that we value. If it wasn’t for the time dimension, it wouldn’t happen.”’

Not all change is adaption. Growth is independent of adaption, and constant churn, what Brand calls graceless turnover, can defeat it. Adaption requires both time and care and reciprocity, the building learning from its occupants and they from it.

How Building’s Learn is a polemical work. I like modernist architecture, and it’s clear why architecture and adaptability are in tension. Why compromise, or even soften, form to serve functions you can’t anticipate. But I also like the idea of scenario planning as part of design methodology. Everything Brand writes about building could be applied to the software development I used to do for a living.

‘Like programming (the problem seeking process of working out the client’s needs and wants), scenario planning is a future-oriented formal process of analysis and decision. Unlike programming, it reaches into the deeper future – typically five to twenty years – and instead of converging on a single path, its whole essence is divergence’

This is a book about buildings, but buildings considered as systems, that is, as composites of interdependent components forming an integrated whole. And everything is composite, and almost everything is a system of one kind or another. Thinking in terms of composition, and the turnover of components through time, discloses the flow, the fluidity, of both the natural world and the built environment, in which the form, function and material composition of components dance around each other as reciprocal constraints.