from How Buildings Learn: What Happens After They're Built
(Penguin, 1994)
By Stewart Brand

CHAPTER 2
Shearing Layers (excerpt)

The leading theorist--practically the only theorist---of change rate in buildings is Frank Dully, cofounder of a British design firm called DEGW (he's the "D"){ and president of the Royal Institute of British Architects for 1993 to 1995. "Our basic argument is that there isn't such a thing as a building," says Duffy. "A building properly conceived is several layers of longevity of built components." He distinguishes, four layers, which he calls Shell, Services, Scenery, and Set.

  • Shell is the structure, which lasts the lifetime of the building (fifty years in Britain, closer to thirty-five in North America). 
  • Services are. the cabling, plumbing, air conditioning, and elevators ("lifts"), which have to be replaced every fifteen years or so. 
  • Scenery is the layout of partitions, dropped ceilings, etc., which changes every five to seven years. 
  • Set is the shifting of furniture by the occupants, often a matter of months or weeks.
Like the advertisers of Architectural Digest, Dully and his architectural partners steered their firm toward the action and the money. DEGW helps rethink and reshape work environments for corporate offices, these days with a global clientele. "We try to have long-term relationships with clients," Duffy says. "The unit of analysis for this isn't the building, it's the use of the building through time. Time is the essence of the real design problem."

I've taken the liberty of expanding Duffy's "four S's"--which are oriented toward interior work in commercial buildings--into a slightly revised, general-purpose "six S's":

Site - This is the geographical setting, the urban location, and the legally defined lot, whose boundaries and context outlast generations of ephemeral buildings. "Site is eternal." Duffy agrees.

Structure - The foundation and load-bearing elements are perilous and expensive to change, so people don't. These are the building. Structural life ranges from 30 to 300 years (but few buildings make it past 60, for other reasons).

Skin - Exterior surfaces now change every 20 years or so, to keep up with fashion or technology, or for wholesale repair. Recent focus on energy costs has led to re-engineered Skins that ale air-tight and better-insulated.

Services - These are tine working guts of a building: communications wiring, electrical wiring, plumbing, sprinkler system, HVAC (heating, ventilating, and air conditioning), and moving parts like elevators and escalators. They wear out or obsolesce every 7 to 15 years. Many buildings are demolished early if their outdated systems are too deeply embedded to replace easily.

Space Plan - The Interior layout--where walls, ceilings, floors, and doors go. Turbulent commercial space can change every 3 years or. so; exceptionally quiet homes might wait 30 years.

Stuff - Chairs, desks, phones, pictures; kitchen appliances, lamps, hairbrushes; all the things that twitch around daily to monthly. Furniture is called mobilia in Italian for good reason.

 Duffy's time-layered perspective is fundamental to understanding how buildings actually behave. The 6-S sequence is precisely followed in both design and construction. As the architect proceeds from drawing to drawing--layer after layer of tracing paper--"What stays fixed in the drawings will stay fixed in the building over time," says architect Peter Caithorpe. "The column grid will be in the bottom layer." Likewise the construction sequence is strictly in order: 
  • Site preparation, 
  • then foundation and framing the Structure, 
  • followed by Skin to keep out the weather, 
  • installation of Services, 
  • and finally Space plan. 
  • Then the tenants truck in their Stuff.
Frank Duffy: "Thinking about buildings in this time-laden way is very practical. As a designer you avoid such classic mistakes as solving a five-minute problem with a fifty-year solution, or vice versa. It legitimizes the existence of different design skills--architects, service engineers, space planners, interior designers---all with their different agendas defined by this time scale. It means you invent building forms which are very adaptive."

The layering also defines how a building relates to people. Organizational levels of responsibility match the pace levels. 

  • The building interacts with individuals at the level of Stuff; 
  • with the tenant organization (or family) at the Space plan level; 
  • with the landlord via the Services (and slower levels) which must be maintained; 
  • with the public via the Skin and entry; 
  • and with the whole community through city or county decisions about the footprint and volume of the Structure 
  • and restrictions on the Site. 
The community does not tell you where to put your desk or your bed; you do not tell the community where the building will go on the Site (unless you're way out in the country).