313structure must be uncovered before it can be read and com-
prehended.
Even a load-bearing structure is not always perceptible
on the surface. To be sure, the construction is accessible to
experience to the extent that the > tectonics of the assembly of
the parts is rendered visually evident. A classic example is the
transitions between temple columns and the architrave and
substructure, which are accented by the presence of capitals
and bases rather than converging without interruption. But
even when the facts of structural assembly along with joint
areas are given visual emphasis, the individual structural rela-
tionships remain a regulated system that is not always avail-
able to perception in the surface appearance of a building. In
our experience, the simple fact that traditionally, most build-
ings are rectangular does not bring the realization that this
form is based on the structural properties of a specific roof
construction, namely the circumstance that as bar-shaped con-
structive elements, beams, stringers and rafters are generally
straight, and are arranged in the simplest way so that one lies
perpendicular to the other. The ‘structural potency’ (Wilkens
2000), however, of this theoretically transferable structure
makes it possible to build a variety of types on its basis.
Confronted with a spatial structure, we initially perceive
only individual spatial forms made up of walls and openings,
while the structure itself remains substantially concealed.
Analytical effort is required before it can be identified as the
system of relationships. Even the layout is not directly per-
ceptible as structure; we experience individual rooms, not the
relationships. More immediately evident, in contrast, are the
spatial relationships that connect parts of the building, which
emerges to view through the access system – the ‘infrastruc-
ture’ of corridors, flights of stairs, and joints – which is reada-
ble almost like a diagram of connecting lines and nodes. Very
different buildings, in fact, share the same spatial structure.
To be sure, the structure of a town or housing estate
shapes life in a given urban district in decisive ways. Nonethe-