In HowBuildingsLearn, StewartBrand analyses buildings as composed of a number of layers or systems. Each system adapts but over a different time-scale. Thus, each system adapts fairly independently, although the inner, faster adapting systems are constrained by the state of the outer, slower adapting system.
Brand calls these Shearing Layers.
Site : almost eternal. The boundaries you have to build within. Normally lasts a long time because whenever you are redeveloping, it's unlikely that your neighbour will be at the same time. Hence your neighbouring sites constrain yours.
Structure : the part that holds your building up. Foundations, supporting columns, load-bearing elements. Typical duration 30 - 300 years.
Skin : Outer cladding. Changes with technology, fashion, repair. 20 years.
services : "Working guts" : piping, wiring, plumbing, air-conditioning, lifts etc. (7-15 years)
Space-plan : Interior layout, interior walls, floors, doors. "Turbulent commercial space can change every 3 years; exceptionally quiet homes might wait 30 years."
Stuff : Furniture, stuff which is moved around monthly.
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