deconstruction). The layersthe six Ssdistinguish between the ways different parts of a building age and change. The Site can be very long-lived, measured in geologic time; the Structure, anywhere from 3 to 300 (typically 50) years; the Skin or exterior envelope, around 20 years; the Services, typically from 7 to 15 years; the Space Plan, like interior partitions, would vary from 3 to 30 years; and the movement of furnishings and other Stuff might be daily or monthly.