Download on the origin of architectural species

InteLLigent
on the origin of architec tur al species
by Matthew Bronski PE
The oft-invoked analogy of the modern building to the human
body (structural frame to skeleton, building enclosure to
skin, mechanical systems to respiratory systems) is as apt as
it is clichéd. Yet it falls short in that the body rather vaguely
described — skeleton, skin, respiratory system — isn’t specifically human, nor even specifically mammalian. The typical
analogy stops short because it doesn’t begin to account for
the vast differences in the bodies and forms of various species
of animal — or building.
In his revolutionary treatise of 1859, On the Origin of
Species, Charles Darwin explained his powerful theory of
the evolution of animal species. By Darwin’s elegant algorithm,
A) if individuals within a group are subject to variation, and B)
if the environment results in a struggle for survival, and C) if
individual characteristics are passed from one generation to
the next, then D) over many generations, a species will evolve
by a process of natural selection, that is, “survival of the fittest.”
Buildings, too, evolve to meet environmental conditions,
with certain architectural forms, details, and materials more
suited to a given climate, site, or use. And, like the animal
species Darwin studied, architectural forms must either adapt
to their conditions — or perish.
In more than 150 years, not a single flaw has been found in
Darwin’s logic. His theory has proven powerful not only for
understanding how the natural world all around us came to be
but also for forming a cornerstone for entirely new lines of
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research and fields of study, such as modern genetics, that
Darwin never imagined.
Given the importance of Darwin’s theory to modern scientific
thought and to cutting-edge scientific research, it is well worth
considering the architectural parallels to his theory. Why do
certain highly evolved building forms look the way they do, and
what can we learn from this to further the state of cutting-edge
architectural design today?
This parallel architectural theory of evolution, which I call
Architectural Darwinism, is most evident in vernacular building
forms, particularly those in harsh climates, where the practical
considerations of creating shelter that worked with its environ­ment were paramount. In vernacular architecture, these
overriding concerns did not yield to stylistic predispositions
or preconceptions, as they occasionally did in more formal
architecture.
In Darwinian biology, the primary mechanism for the
evolution is entirely involuntary (natural selection), whereas
in Architectural Darwinism, the mechanisms are both voluntary
and involuntary. The involuntary mechanism occurs where
buildings with more advantageous variations and traits are more
likely to survive over the centuries, and those buildings that
were not as durably designed and constructed tend to fall prey
to the effects of time and weather. The voluntary mechanism
occurs where humans have carefully observed what has worked
and what hasn’t, and affirmatively designed the next building
Design
with the individual variations that have empirically proven to
work well — a certain chimney location, a certain roof eave
framing detail, a certain overall building form. In this way, the
advantageous variation or trait is typically passed to the next
generation of vernacular buildings.
Sometimes the technical logic behind the advantageous trait,
and hence the evolution of a vernacular species, is fairly obvious.
Second period (1725–75) “colonial” houses in New England
were virtually the same as those in the South, except the
northern version of the species had a very large central chimney
to retain as much heat as possible within the house, and the
southern version had the chimney on an outside wall, to cast off
as much heat as possible to the exterior.
Just as obviously, antebellum plantation houses in hot,
humid, flood-prone Louisiana were often raised on brick piers
with an open ground floor, so that floods could wash through
without damage. Further, a veranda wrapping all around the
house shaded windows from the sun while allowing breezes
through, tall windows and a square floor plan promoted cross
breezes, and louvered attic dormers or a cupola passively
vented and exhausted naturally rising hot air. All these
advantageous characteristics evolved long before “resiliency”
or “sustainability” or “passive design” became buzzwords.
More often, the logic is not obvious, and highly evolved
technical details are mistaken for mere stylistic or ornamental
traditions. At first glance, the use of large diamond-shaped slate
roof shingles in the vernacular architecture of the Alps (as
opposed to smaller, rectangular slate shingles common in the
United States and England) may seem a stylistic tradition rather
than a technical evolution. However, on closer examination and
THIS spread
Galapagos finches by John Gould, from
Darwin’s Voyage of the Beagle, 1845.
analysis, the larger, diamond-shaped shingles are far more
efficient in their use of material and in their resistance to
wind-driven rain than their rectangular counterparts (Fig. 1).
Similarly, the highly evolved technical logic of the traditional
roof eave framing detail found in Rome is not readily apparent,
and this beautiful detail could easily be mistaken for the purely
ornamental (Fig. 2). The detail transcends vastly different
architectural periods and styles, from antiquity through the
Medieval, Renaissance, and Baroque, to late 19th- and early20th-century Neo-Classicism, a strong clue that it is not merely
stylistic. Its track record of durability is truly remarkable. Many
examples, several hundred years old, constructed of relatively
nondurable wood species such as pine, survive outdoors —
unpainted, untreated, in a relatively rainy climate.
The triangular form of the projecting beam end is exactly
“what it wants to be” structurally. The triangular cut not only
eliminates the portion of the beam end that is not needed
structurally but also eliminates the portion that would tend to
rot (via wicking of moisture through the exposed end) if the
beam were simply cut at 90 degrees. The deep overhang of the
roof over the beam protects it from moisture under all but
the most severe wind-driven rain events. When rain does
occasionally wet the beam, a series of beautiful but entirely
functional cuts along the diagonal edge of the beam create drip
edges to shed water at regular intervals. With such thoughtful,
durable design, it is no wonder this detail has survived so well
for centuries, despite the vulnerability of pine to rot in the
humid, rainy climate of Rome.
Like the Roman eave detail, other highly evolved vernacular
details and forms use local materials that are not, in and of
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Figure 1 Diamond-shaped slate roof
shingles in the Alps are more technically
evolved than rectangular shingles because
they use the material more efficiently and
are more consistently watertight.
Photo: ©iStock.com/koufax73.
themselves, durable within the local climate but have
become durable through good design. The halftimbered buildings of England and central Europe
are remarkable for the way the building form makes
materials that degrade quickly with moisture perform
durably even in a rainy climate. The materials they
are built from, wattle (wood wicker) and daub (lime
or clay plaster) degrade quite rapidly if left out in the
rain, but the overall building form of an inverted
stepped pyramid with cantilevered overhangs
(known as jetties) at each floor serves to make the
construction durable, even in the rain. The jettied
overhangs shelter the walls from rain and shed
water directly to the ground (not to the wall
below), thus reducing the maximum possible
accumulation of moisture at any point on the wattle
and daub.
Darwin’s revolutionary theory of evolution
was based in part on his careful observation,
documentation, and consideration of apparently
ordinary things he saw around him on his
voyages — for example, the slight differences in the
shapes of the beaks of finches or in the thickness and
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STRUCTURAL FORM-FINDING
Min. moment (Ø)
Shear
shape of the shells of tortoises on the various islands
of the Galapagos. The highly evolved vernacular
forms of the English half-timbered, jettied building;
the Alpine Swiss chalet; the antebellum Louisiana
plantation house; and countless others are analogous
to Darwin’s finches and the Galapagos tortoises.
Though none is immortal or invulnerable, each
evolved to be particularly well suited to survival in its
respective environment.
Darwin’s masterful theory has been hailed as
“the greatest idea anyone ever had” and continues to
enable cutting-edge scientific research 150 years later.
But his method — careful observation of the details all
around us, and clear, simple analytical reasoning — is available to us all. In this age of global climate
crisis, it has never been more important to analyze
the details of highly evolved vernacular forms for the
broad lessons they have to teach us about resilient,
durable, sustainable design. If we can incorporate
these lessons into our conception of the overall forms
and details of building designs, we’ll be far more
responsive and responsible in meeting the formid­
able environmental imperative confronting us today. ■
Max. moment
material degradation
Survives
gravity
rots
capillary action
water management
Figure 2 The triangular cut of Rome’s roof
eave framing eliminates the beam end
that is not needed structurally and the
portion that would tend to rot. The roofing
protects the beam from rain, and a series of
functional cuts create regular drip edges to
shed water. Illustration: Matthew Bronski pe.
need drip edges
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