Architects design buildings, but architecture is more than just building design and more than just art on a massive scale. Architecture is about light and space. It is about stimulating emotions in the people who see and inhabit the structure. Architecture creates an environment, whether it is the uplifted spirituality of the Chartres Cathedral, the drama and anticipation of the Schauspielhaus auditorium, or tranquil serenity of Frank Lloyd Wright’s (1867–1959) Fallingwater. It is experiential. When you approach or enter a building you move through the space, the scale changes, the proportions shift around you. This is what makes architecture glorious; the way it manipulates light.
Structure is fundamental to architecture. For a design to move from the mind of the architect to reality, there must be a method of building it. The development of structural forms has thus been a driving force in architecture, every bit as much as changes in social order and historical events. Through history there have been relatively quiet periods of stylistic development, interspersed with almost muscular leaps of structural innovation such as the Roman period, the Gothic period or the Industrial Revolution.
The architecture of prehistory is largely one of tombs and temples, though mudbrick Neolithic settlements have been discovered. Houses in these settlements were one-story, rectangular structures with a hole in the roof that served as both chimney and entry. The doorway, with its horizontal lintel and vertical posts, was developed somewhat later and constitutes the first significant leap forward in architecture, making all future styles possible. The architectural term for post-and-lintel construction is trabeation. Trabeated passages, some involving enormous stones, were built into huge mounds of earth to form burial tombs called barrows.
The thought of the ancient Egyptians immediately brings the image of the pyramids to mind, but architecturally speaking, the advances they made with materials and design were far more important. The Egyptians built structures as we know them, with walls, trabeated doorways, and small window openings. They eventually developed the freestanding column, which allowed them to build enormous halls with trabeated roofs, structures that essentially consisted of parallel rows of post-and-lintel constructions.
The emphasis of ancient Egyptian architecture was on mass rather than space, typified by the Hypostyle hall where some of the columns are 11 or 12 feet (3.5-4 m) in diameter. The structural strength of the lintel in a trabeated roof limits the expanse of open space that can be spanned by this method. When the lintel is too long, the load carried by the stone is greater than its strength, and it fails. Thus, the open space in Egyptian halls was very limited, though the ceilings soared to heights of almost 70 feet (21 m) and the actual halls were hundreds of feet wide.
The Egyptians were the first structural designers with an identifiable visual style. Their temples and tombs had such a strong identity and coherence that architects still echo their designs in modern structures. They drew some of their inspiration from nature, carving columns to look like palms, or plants crowned with papyrus or lotus blossoms. Structures were also designed to elicit emotions in the viewers, such as the temples interiors that progressed from the bright, relatively open spaces allowed to the public, to the dim, confined spaces of the inner sanctum, accessible only to the priests and rulers. Both the use of nature in architectural decoration and the use of design to control emotion were themes that would be repeated over and over in coming centuries.
The architecture of the Near Eastern civilizations that coexisted with the Egyptians evolved distinct identities. The Sumerians, for example, had little access to stone. Their available building material was mudbrick, a structurally weak material that could not produce the lintels required for trabeated roofing. To solve the problem of roofing, the Sumerians are believed to have developed the curved arch and tunnel vault to enclose narrow interior spaces. The ancient Persians had access to a variety of building materials, and they were influenced by the architecture of the Egyptians, the Greeks, and the other civilizations that inhabited their enormous empire. With such rich source material, they were able to develop a unique, fanciful architectural style, and structurally refine the approach of the ancient Egyptians. In the royal audience hall in Persopolis, the ancient capital, the pillars were half the diameter of the Egyptian columns, with a significantly wider spacing than the Egyptian version. The ceiling was still trabeated, but the effect is of a much lighter, much more open space.
Ancient Greek architecture was a miracle of style, balance, and harmony, with a powerful simplicity whose influence persists in architecture to this day. It is distinctive and immediately recognizable, a graceful massing that creates a sense of dignity, wisdom, and timelessness. The Greeks believed in human intellect and rational thought, in community, and the achievements of the living, rather than the cult of death featured in earlier civilizations. Accordingly, their architectural focus was on public buildings: temples, theaters, civic structures. They were the pioneers of city planning.
Greek society was built upon democracy, stressing the involvement of the individual in government and culture. This was reflected in their architecture. Structures were rarely aligned with one another but were instead set at angles to enhance the individuality of the structures and draw the viewer into participating in the process. The viewer’s viewpoint was not strictly regimented, as we will see in later eras, but instead allowed to form naturally.
The elements of classical Greek structures are simple and few, yet carefully organized to create an overall effect. The primary structural form was trabeation—stone columns supporting lintels. There were three styles, or orders, of Greek architecture: the Doric, the Ionic—distinct styles that originated in different parts of the country, and the Corinthian, which is essentially a spin off of the Ionic order. The structural elements, proportions, and composition of a building were defined by its order. Doric structures, in particular, followed a rigidly prescribed design, evolving toward the ideal Doric form expressed in the Parthenon. Symmetry of proportion runs through the structures, with set ratios of building length to width, and column height, diameter, and spacing. The Ionic style was less rigidly defined than the Doric, though proportion was still important, and the Corinthian order differed from the Ionic only in column design. In fact, the names of the orders are most often associated with the capitals or decorative tops of the columns used in the buildings. Doric columns are simple angled tops, Ionic columns are delicate scrolls, and Corinthian columns are crowned with a delicate, leafy capital.
Roman philosophy and engineering fundamentally changed the way people thought about architecture. The Romans took previously invented structural elements, such as the arch and vault, to the limits of their potential. The Greeks, for example, dabbled with concrete and in later periods occasionally used arches, but only as freestanding decorative elements. In the hands of the Romans, these same two concepts were used to build the Colosseum.
The development of the rounded arch was critical to Roman architecture. In our earlier discussion of trabeation, we pointed out the lintel as the weak element of the structure. The tensile strength of the lintel limits the size of the opening and the load that can be carried, because the load on the lintel is only supported at the ends. In the nonsupported portion of the lintel, the lines of force are aimed through the lintel to the ground. In an arch, on the other hand, the lines of force from the load are directed through the curve of the arch to the supporting piers, and from there to the ground. The supporting pier strength is limited by the compressive strength of the stone, which is far greater than its tensile strength. Moreover, the form of the arch and arch elements is such that the structure actually becomes stronger with a uniform load placed on top of it.
Rounded arches can be placed in a row to make a barrel vault, which means that a significant amount of space can be roofed over. The Romans developed a number of variations on the barrel vault, changing the way that space could be enclosed. The disadvantage of the barrel vault is that it requires continuous support along the sides, limiting the number of window openings permitted in the sidewalls. One answer to this was the groin vault, a structure consisting of two intersecting barrel vaults. Whereas the weight and force of the barrel vault is carried all along the line of the supporting wall, the groin vault concentrates weight and force in the corners of the structure, permitting a more open space and windows. The hemispherical dome, which can be thought of as an arch in three dimensions, was another variation on roofing. This form appears time and time again in Roman architecture, most notably in the Pantheon.
Another important Roman development was that of improved concrete. For several centuries, a concrete made of lime, sand, and water had been used sporadically by various builders. The Romans added a volcanic ash called pozzolana to their concrete, obtaining a stronger mortar that had the added advantage of setting up in water, allowing underwater construction. The Romans mixed this concrete with gravel or chips of stone and molded it into blocks or even arches and vaults, simplifying construction methods.
The Romans considered architecture differently than the Greeks, who emphasized structure and form; the Romans emphasized space. Whereas Greek architecture was exterior, focused on the outside, on creating an experience for the viewer, Roman architecture was interior, based on the idea of creating an environment for the inhabitants. The Romans were more pragmatic than spiritual. Rather than focusing on temples, they built sumptuous bathhouses, theaters, and other public spaces. Great administrators, they created the basilica to house government offices. The interiors of their buildings focused on space, on creating spaces to serve man, spaces that were emotionally and functionally pleasing. The Romans were also sophisticated urban planners, designing free form civic centers, or forums, and rigidly styled castrum, a combination military outpost/colonial settlement in newly conquered territory.
After the fall of the western Roman Empire, the creative focus of architecture moved to Constantinople, located at the site of the Hellenic city of Byzantium. Most of the surviving structures from this period are churches. Rather than the long, axial floor plan characteristic of Roman barrel vaulted structures, Byzantine designs tended toward a centralized, vertically focused structure crowned with a dome that flooded the interior with light. Light, form, and structure in these churches were orchestrated to express the spiritual ideas of the new Christian religion, to exalt the worshippers.
Byzantine churches achieved the floating effect of the central dome by the use of pendentives and pendentive domes. A hemispherical dome requires a circular base to support it fully, like that on the Pantheon. Interior spaces, however, tend to be square. Ancient architects wishing to top a noncircular space by a spherical dome added diagonal elements across the corners, called squinches, which helped support the structure. The Romans developed a more sophisticated method of support called the pendentive, a spherical, inverted triangle that rises from its point and curves downward. It is essentially a section of a domed surface and as such can be constructed to fully support a hemispherical dome. More important than the full support, though, is the nature of that support. The structural support of a dome on a cylinder or on squinches is visually dense, giving a sense of massing and of enclosure. A dome on pendentives appears to rise from only four points, giving the impression of floating overhead, adding to the otherworldly effect of the church interior.
The spiritual effect of the floating domes was enhanced by the use of light and ornamentation. Hagia Sophia, the most spectacular of the Byzantine churches, is flooded with light from a multitude of wall openings. A row of windows around the base of the dome adds to the impression of a magically hovering surface, as do the additional half-domes and colonnades in the lower levels. To look up from the floor of the building is to look into a gleaming, billowing surface that appears to follow no known rules of structure, generating an exaltation of religion in its intensity.
In the medieval period, European architects were profoundly influenced by the Roman structures dotting the countryside. A style known as Romanesque emerged, featuring the Roman hallmarks of rounded arches and barrel vaults. Because barrel vaults must be supported continuously along the sides, these structures had few windows. The focus was on an almost claustrophobic massing: thick walls, small windows, heavy, ponderous piers.
The lines of force in an arch are designed to run down into the supporting column or piers. When the load is too extreme, as in the case of the large vaults of the Romanesque cathedrals, the lines of force are shifted laterally, with the result that the base of the arch tends to push outward from its supporting column. To prevent this, the Romanesque designers added buttresses, massive piers of masonry built against the walls at critical points to resist the lateral stress. Structurally it was effective, but it only added to the oppressive feel of the buildings.
Romanesque was primarily an adaptation of existing ideas, but the Gothic period was one of profound innovation. Elements were developed that allowed interior space to be approached in a way it had not been before. In contrast to the heavy inertness of the Romanesque structures, the Gothic cathedrals were open and buoyant, with a dynamic use of space. If Byzantine churches like Hagia Sophia gave an impression of the otherworldly, to the medieval peasant unused to any but the smallest interior spaces, the soaring lines of the Gothic cathedrals with their brilliantly colored walls of glass and traceries of stone must have felt like heaven.
The rounded arch is a powerful structural element but it has its limitations. Force applied to the rounded arch is carried along the full arc and driven into the supports of the arch. When the applied load is too high, however, the lines of force move outside of the structure of the arch; in such a case, the arch fails. The arch developed by the Gothic cathedral builders was pointed, rather than rounded. Its lines described a catenary arc rather than a hemisphere, keeping the lines of force within the structure of the arch so that the load applied to the arch was deflected straight down through the arch supports to the ground. The Gothic arch is more stable and can be thinner than the same size rounded arch. This allowed the Cathedral designers to build larger, lighter-looking structures.
A second important development of the Gothic period was the rib vault. Romanesque naves were roofed with barrel vaults, essentially a line of rounded arches. Load applied to the vault was carried all along the wall holding up the arch. This limited the number of openings possible in the wall, leading to the claus-trophobically small and infrequent windows of the Romanesque churches. Groin vaults made from the intersection of two barrel vaults permitted a somewhat wider open space, but again the load on the vault was carried by the arches. Groin vaults carried the load in the corners, allowing more openings in the walls, but they were difficult to build and could only span a square area. The rib vault represented a new concept in structure.
The rib vault consists of six arches: the arches on each side and a pair of transverse arches. The roofing of the vault is just a thin, relatively lightweight layer of stone webbed over this supporting structure. Load is minimized and carried at the corners of the vault. Construction is dramatically simplified. Design of the rib vault is facilitated by the pointed arch, which allows the vault to be any variety of rectangle, as opposed to the square vault dictated by use of rounded arches. The development of the rib vault allowed the cathedral architects to roof over enormous spaces. Because the vaults carried the load to the corners of the vault, the need for massive load-bearing walls was gone. The Gothic builders were able to open enormous holes in the walls without compromising the structure, and the Cathedrals became traceries of stone filled with stained glass.
The third major development of Gothic architecture was the flying buttress. Romanesque churches used massive piers to support their sidewalls, the inertial bulk resisting the side forces created by the load of the ceiling. The flying buttress is a half-arch that connects to a massive pier. It allowed the Gothic architects to apply resistive force to the ceiling loads at the point needed, rather than simply building huge piers and hoping they would not fail. The flying buttresses allowed the Cathedrals to soar to heights well over 100 feet (30 m). Moreover, they lightened the feel of the cathedral exteriors, making them appear like lace-work, fragile and airy.
The Renaissance and the Baroque
Renaissance architecture was a response to the ornamentation of the Gothic period and an homage to the new values of symmetry, balance, logic, and order. Man was once again exerting control over his environment, and the structures of this time reflected the dedication to mathematical forms and the ordering of space. The innovations of Renaissance architecture are less structural than paradigmatical. Leon Battista Alberti (1404-1472) codified what was known of architecture, emphasizing the theoretical aspects, turning it from a trade into a profession. More importantly, he developed perspective drawing techniques that allowed architects to draw accurate architectural renderings, techniques that are still used today.
Like the Renaissance, the Baroque period was marked by design rather than structural innovation. In response to the bareness of Renaissance architecture, Baroque buildings were lavishly decorated. Rather than have form follow function, designers of this period approached architecture as theater, emphasizing effects, interpretations, and movement. The Spanish Steps in Rome, for instance, were designed to mimic the movements of a popular dance of the time, with sidewalls that moved in, moved out, met, separated, and met again. Design elements became more emotional and dynamic, with a focus on energy versus balance. At the same time, underlying the ornateness of the Baroque was the logic of Renaissance design.
One notable aspect of Baroque architecture was its use of controlled viewing to emphasize a building. The approach to St. Peter’s in Rome is a classic example: It was carefully orchestrated, beginning some blocks away with the Ponte Sant’ Angelo, progressing through a tangle of narrow streets that heighten anticipation by providing only glimpses of St. Peter’s. Finally, the pilgrim emerged into an enormous oval piazza that permitted a clear view of St. Peter’s for the first time, framed by the curved colonnade. The sequence was designed to enhance the religious experience of St. Peter’s by intensifying the emotions— creating a sense of anticipation and delayed gratification—felt during the approach.
The Industrial Revolution—new materials
After the Baroque faded slowly away, eighteenth-century architecture consisted primarily of revivals of previous periods. This time was to be the calm before the storm, for the approaching Industrial Revolution was to change everything about the world as it was then, including architecture. Previously, building materials had been restricted to a few man-made materials along with those available in nature: timber, stone, lime mortar, and concrete. Metals were not available in sufficient quantity or consistent enough quality to be used as anything more than ornamentation. Structure was limited by the capabilities of natural materials. The Industrial Revolution changed this situation dramatically.
In 1800, the worldwide production of iron was 825,000 tons. By 1900, with the Industrial Revolution in full swing, worldwide production stood at 40 million tons, almost fifty times as much. Iron was available in three forms. The least processed form, cast iron, was brittle, due to a high percentage of impurities. It still displayed impressive compressive strength, however. Wrought iron was more refined and malleable, though with low tensile strength. Steel was the strongest, most versatile form of iron. Through a conversion process, all of the impurities were burned out of the iron ore, then precise amounts of carbon were added for hardness. Steel had tensile and compressive strength greater than any material previously available, and its capabilities would revolutionize architecture.
This change did not happen over night. Prior to the introduction of bulk iron, architecture relied on compressive strength to hold buildings up. Even great structures like the Chartres Cathedral or the Parthenon were essentially orderly piles of stone. Architects were accustomed to thinking of certain ways of creating structure, and though they glimpsed some of the possibilities of the new materials, the first applications were made using the old ideas.
The explosion in the development of iron and steel structures was driven initially by the advance of the railroads. Bridges were required to span gorges and rivers. In 1779, the first iron bridge was built across the Severn River in Coalbrookdale, England. It was not an iron bridge as we might conceive of it today, but rather a traditional arch made of iron instead of stone. The compressive strength of limestone is 20 tons per square foot. The compressive strength of cast iron is 10 tons per square inch, 72 times as high, permitting significantly larger spans. Later, the truss, long used in timber roofs, became the primary element of bridge building. A triangle is the strongest structural element known, and applied force only makes it more stable. When a diagonal is added to a square, the form can be viewed as two triangles sharing a side, the fundamental element of a truss. Trusses were used to build bridges of unprecedented strength throughout the nineteenth century, including cantilever bridges consisting of truss complexes balanced on supporting piers. A third, more attractive type of steel bridge was the suspension bridge, in which the roadway is hung from steel cables strung from supporting towers in giant catenary arcs.
As with bridges, some of the first structural advances using steel were prompted by the railroads. Trains required bridges and rails to get them where they were going, but once there, they required a depot and storage sheds. These sheds had to be of an unprecedented scale, large enough to enclose several tracks and high enough to allow smoke and fumes to dissipate. Trusses spanned the open area of the tracks, creating a steel skeleton hung with steel-framed glass panes. The structures were extraordinarily light and open. Some of the sheds were huge, such as St. Pancras Station, London, England. To the people of the nineteenth century these sheds were breathtaking, the largest contiguous enclosed space the world had ever seen.
At this point the capabilities of iron and steel had been proven and it was natural to extend the idea to another utilitarian application—factories. The first iron frame factory was built in 1796-1797 in Shrewsbury, England, followed rapidly by a seven-story cotton mill with cast-iron columns and ceiling beams. Wrought-iron beams were developed in 1850, a significant advance over brittle cast-iron versions.
Barrel vault— A vault made of a series of rounded arches.
Buttress— A strong stone pier built against a wall to give additional strength. (Flying buttresses extend quite far out from the wall.) A buttress must be bonded to the wall.
Curtain wall— A non-load-bearing façade that is supported by the steel frame of the building.
Flying buttress— A buttress incorporating arches that applies force at the arch/column interface.
Groin vault— A vault made of the intersection of two barrel vaults.
Nave— The long central portion of a church or Cathedral.
Pendentive— An inverted concave masonry triangle used to support a hemispherical dome.
Piazza— Italian for plaza or square.
Pier— A vertical support element, usually extremely massive.
Post and lintel— A structural form consisting of a horizontal element (lintel) resting on two support posts. Also called trabeation.
Squinch— Diagonal elements crossing the corners of a rectangular room to supply additional support for a dome.
Trabeation— A structural form consisting of a horizontal element (lintel) resting on two support posts. Also called post and lintel construction. Truss—A very light, yet extremely strong structural form consisting of triangular elements, usually made of iron, steel, or wood.
Vault— A roof made using various types of arches.
The new materials were not just used as skeletal elements. In the 1850s, 1860s, and 1870s, cast iron was used as a facŖade treatment, especially in the Soho district of New York City. Buildings such as the Milan Galleria, an indoor shopping area, and the Bibliothèque Nationale in Paris used iron as an internal structural and decorative element. In 1851, the Crystal Palace was built for the London Exposition, truly the Chartres Cathedral of its time. In 1889, Gustav Eiffel built the Eiffel Tower for the Exposition Universelle in Paris, initially a target of harsh criticism and now the symbol of Paris.
The Industrial Revolution provided more than just ferrous building materials. A stronger, more durable and fire-resistant type of cement called Portland Cement was developed in 1824. The new material was still limited by low tensile strength, however, and could not be used in many structural applications. By a stroke of good fortune, the thermal expansion properties of the new cement were almost identical to those of iron and steel. In a creative leap, nineteenth-century builders came up with the idea of reinforced concrete. Though expensive, iron and steel had high tensile strength and could be easily formed into long, thin bars. Enclosed in cheap, easily formed concrete, the bars were protected from fire and weather. The result was a strong, economical, easily produced structural member that could take almost any form imaginable, including columns, beams, arches, vaults, and decorative elements. It is still one of the most common building materials used today.
In the mid-nineteenth century, French architect Eugeℒne-Emmanuel Viollet-le-Duc published a series of tracts on architecture. He decried the fact that with the notable exception of engineers like Eiffel, new structures were being built with old methods. In the face of the new material, architects had either substituted the new material for the old (the Coalbrookdale Bridge), or adapted old methods to the new material (the truss). What architecture needed, according to Viollet, was to uncover new methods that tapped the potential of the new materials.
Some of the most significant advances in architecture at this point were made by a group of architects collectively known as the Chicago School, developers of the modern skyscraper, which was developed in response to the rising price of city land. To maximize use of ground space, it was necessary to construct buildings sixteen or more stories tall. Initial attempts included iron-frame construction with heavy masonry walls requiring massive, space-consuming piers. This was an extension of the traditional methods in which the exterior walls of a building added structural support, unnecessary in the face of iron/steel framing. The approach was merely an adaptation at a time when a completely new approach was needed.
The solution, developed in Chicago, was to separate the load-bearing frame of the building from a nonstructural facŖade. The facŖade became a curtain wall that was supported by the steel frame, story by story. Because the facŖade material on a given story supported only itself, it could be very light and thin. The further evolution of this approach by architects of the Chicago School led to the modern skyscraper, with its fireproof steel frame, curtain wall facŖade, and internal wind bracing.
Much of the architecture of the twentieth century has been a process of refinement, of learning to work with the multitude of new materials and techniques presented by the Industrial Revolution. Various movements, such as art nouveau, art deco, modernism, and postmodernism have all been about design and ornamentation rather than major structural innovation. Certainly, architects during this period have explored the possibilities of the new materials and construction techniques. Most recently, however, architecture has been working through a revival period in which old styles are being reinterpreted, similar to the eighteenth century. Perhaps, like the eighteenth century, we are poised at the start of a new period of innovation.
This entry is only a brief discussion of the role of technical advances in the history of architecture. It is by no means a thorough discussion of architecture itself. Technology permits architecture, but architecture is not about technology. Architecture can perhaps best be expressed in the words of Le Corbusier, one of the most influential architects of the twentieth century: “You employ stone, wood, concrete, and with these materials you build houses and palaces. This is construction. Ingenuity is at work. But suddenly you touch my heart, you do me good, I am happy and I say ‘This is beautiful.’ That is Architecture. Art enters in.”
Allen, Edward. The Architect’s Studio Companion. 3rd ed. New York: John Wiley & Sons, 2001.
Allen, Edward. Fundamentals of Building Construction. 3rd ed. New York: John Wiley & Sons, 1998.
Ching, Francis D. Architecture: Space, Form, and Order. New York: Van Nostrand Reinhold, 1979.
McCoy, Esther. Case Study Houses, 1945-1962. Santa Monica, CA: Hennessey & Dyalls Inc., 1977.
Trachtenberg, Marvin, and Isabelle Hyman, Architecture from Prehistory to Postmodern. Englewood Cliffs, NJ: Prentice Hall Inc., 1986.
Thais. “40 Centuries of Architecture” <http://www.thais.it/architettura/default_uk.htm> (accessed November 6, 2006).