Domes (architecture)

Summary: Domes have been used throughout history to cover open spaces.

In architecture, a dome is a hemispherical structure with a circular, polygonal, or elliptical base that is usually used to cover a large open space. It developed as a generalization of the full revolution of an arch around a vertical axis.

Early domes appeared in small buildings and tombs of the ancient Middle East, India, and the Mediterranean. Because these domes consist of horizontal layers of materials progressively cantilevered inward until they reach the top of the roof, they are considered “false domes” and called “corbel domes.” True domes present the characteristic of having a continuously changing slope ranging from being vertical at the base to horizontal at the top, which requires adaptable roofing materials.

Large-scale masonry domes were first introduced by the Romans in public buildings, such as baths, temples, mausoleums, and basilicas. With an interior diameter of 142 feet, the Pantheon, built during the second century in Rome, remained the largest dome until 1881 and is still the world’s largest unreinforced concrete dome. Built on a rotunda, it exerts tremendous thrusts on the perimeter walls. It is not only an engineering triumph but also a tremendous achievement in sacred geometry and cosmography. Its hemispherical ceiling has regularly been compared to the vault of heaven.

Carried on four pendentives, the 102-foot central dome that covers Hagia Sophia in Istanbul is a masterpiece of Byzantine architecture. Built in the sixth century, it exemplifies the full development of the pendentive (a triangular segment of a sphere) as a constructive solution allowing the construction of a dome over a square nave. Volumetric transitions and intersections are critical components of the geometry of architecture.

Built from 1420 to 1436 under the direction of Brunelleschi, the dome of Santa Maria del Fiore in Florence succeeded Hagia Sophia as the largest masonry dome in the world, a record it stills holds. Brunelleschi designed an eight-sided double dome shell without exterior buttresses that did not require any supporting framework during construction. Standing at about 165 feet above ground level, the interior of the dome is approximately 100 feet tall and spans 139 feet. The dome weighs more than 40,000 tons and required the use of more than 4 million bricks.

Domes became increasingly popular during the Renaissance, the Baroque era, and the nineteenth century. Influenced by the Pantheon and Santa Maria del Fiore Bramante, Michelangelo designed St. Peter’s Basilica in Rome.

It has the world’s tallest dome, and it inspired one of the most famous landmarks of Baroque architecture: the dome of the Invalides designed by Mansart. Completed in 1711, Wren’s three-layer dome for St. Paul cathedral in London influenced the construction of the dome of the U.S. Capitol in Washington, D.C., which ultimately inspired the design of most U.S. state capitols.

Since the late nineteenth century, different materials, such as steel, wood, membrane, and reinforced concrete, have allowed the building of domes covering much larger spaces. The two monumental arches supporting the retractable roof of the Cowboys Stadium in Arlington, Texas, reach a height of 292 feet and span of 1225 feet—making it the largest domed stadium in the world.

Geodesic domes represent another modern type of dome, rejecting the classical arch principle. This type of dome is usually a partially spherical structure constituted of a network of triangular or polygonal facets that are in tension and compression. Because the thrust is equal in all directions, the dome can be anchored directly on the ground. Because of their cost-effectiveness and structural strength, hundreds of thousands of geodesic domes have been built all over the world—most often as a solution to provide shelter for poor families in developing countries, or to house people in extreme weather conditions. In 1960, Buckminster Fuller, who developed the mathematics of this type of dome, designed a geodesic dome two miles in diameter and one mile high at its top that would have covered Midtown Manhattan, and provided the whole district with permanent climate control.

Bibliography

Blackwell, William. Geometry in Architecture. Boston: John Wiley and Sons, Inc., 1984.

Hammond, Victoria. Visions of Heaven: The Dome in European Architecture. New York: Princeton Architectural Press, 2005.

Kenner, Hugh. Geodesic Math and How to Use It. 2nd ed. Berkeley: University of California Press, 2003.

King, Ross. Brunelleschi’s Dome: How a Renaissance Genius Reinvented Architecture. New York: Penguin Books, 2000.

McDonald, William L. The Pantheon: Design, Meaning, and Progeny. 2nd ed. Cambridge, MA: Harvard University Press, 2002.