Republican Roman Construction 3, by Judith Geary
Ruins often reveal that stone or brick was precisely laid at a building´s front, corners and around doorways, and less regularly at the back and the walls between. The image below shows an example of this type of construction at Pompeii.
Sometimes these "important" places were cut stone and the walls between of some other material, mud bricks or mortar and rubble. Vitruvius reports that "basketwork," lath or cane woven together and covered with mortar or plaster, might be used by the poor or for interior walls, particularly on upper stories. This construction was neither moisture resistant nor fireproof, but it was lightweight, cheap and quickly built. Of course, these walls have not survived.
About the third century BCE, Roman builders discovered that volcanic ash, when added to lime mortar, made a cement that cured to a rocklike hardness even under water. Mixed with sand and gravel, this material was the equivalent of modern concrete. At first concrete was used like a particularly durable mortar, or for places where its ability to harden without drying out was important-for the water courses of aquaducts and for bridge pilings, for example.
Concrete gradually caught on for construction of homes and public buildings, but not in the sense it has in modern times, when architects have taken advantage of the characteristics of the material to create soaring skyscrapers, fantastic shapes and homes cantilevered out over waterfalls. (The soaring dome of Hadrian´s Pantheon is an example of a particularly sophisticated concrete design, but that´s a product of the Empire.) In the time of the Republic, the core of a wall would be concrete, but the facings remained brick or stone. At first, the concrete might be poured between facings of masonry, and layers of rubble added. Eventually, walls became essentially a mass of concrete, poured into a wooden form and finished before it was completely set. The old terms acquired new meanings. Opus testaceum referred to a concrete wall in which wedge-shaped pieces of brick were inserted, point first, so that the wall appeared to be of laid brick. Opus incertum referred to a concrete wall in which irregular chunks of stone were pressed into the soft concrete. When the concrete set, the stones were chiseled down even with the concrete surface. Opus reticulatum, or "netlike work" in which little square pyramids of stone were inserted point first in a diamond pattern, became quite popular. This pattern appears as the flat surfaces of walls between corners of laid brick or stone. According to Vitruvius, opus incertum is an "ancient style," and opus reticulatum, while not as strong, is the "style used by everybody."
We might ask ourselves why Roman builders bothered with facings of brick or stone for concrete walls. They certainly added nothing to the strength, and they were covered in the finished wall with plaster and paint. The striking opus reticulatum walls we see today at Pompeii and other ruins were likely not visible when the buildings were in use. Perhaps we can look to the basic conservatism of the Roman people. If a man was paying to have a wall built, he expected to see brick or stone.
We have inherited much from the early Romans. Constructing a picture for ourselves of builders of Republican Rome, we find they share many characteristics with modern builders. They were capable of building monuments of enduring beauty and grandeur. However, they were also guilty of taking particular care with the parts of the building that "showed," and less with the parts that did not. The Romans had "faux-finishes" on walls and columns. They used plaster and stucco to simulate carvings of stone and wood. So the designer faux wallpapers, plastic crown moldings and ceiling medallions of modern homes may be more traditional than we think.
© Judith Geary 2000. Photos © Judith Geary
Adkins, Lesley & Roy A. Adkins, Handbook to Life in Ancient Rome Facts on File, New York, 1994.
De Camp, L. Sprague, The Ancient Engineers Barnes & Noble Books, 1993.
GimbH, E.T.V., Architecture of the World: The Roman Empire Compagnie du Liver d'Art, S.A., Lausanne, Germany, (no date given).
Morgan, Morris Hicky, trans., Vitruvius: The Ten Books on Architecture Dover Publications, Inc., New York, 1960 ed.