Page 91 - Between light and shade

Shade

The shadow line
The “shadow line” rule can be expressed as fol-
lows: “except in the case of special conditions,
which are precisely defined and restricted, all
construction elements subject to the influence
of bad weather must be characterised in terms
of elevation by a horizontal shadow line, which
highlights the difference in the depth of the walls
required by the law of construction.”

This rule applies to all construction elements,
both opaque and transparent, but its expression
is not the same for these two categories of objects.
For opaque materials, the shadow line is a single
dark strip, whose width is proportional to the
extent of the difference in depth. For transparent
materials, it plays a part in the complex interplay
of reflections by locally replacing the reflected
image with a darker transparent strip.

The shadow line has a very long history.
At any time and anywhere, vernacular
constructions 2 in high rainfall regions generally
have a roof that overhangs the walls to protect
them from rain, whilst projecting the “original”
shadow line.
This arrangement is “translated” in stone
by erudite ancient architecture, in the form

2 The Encyclopedia of Vernacular Architecture of the World
(Paul Oliver ed., Cambridge University Press, 1997 ; in three
volumes) documents the subject in a rigorous and comprehen-
sive manner.

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