Ancient Roman masonry using irregular stones in a core of concrete
Opus incertum on the Temple of Jupiter Anxur in Terracina, Italy
Opus incertum ("irregular work") was an ancient Roman construction technique, using irregularly shaped and randomly placed uncut stones or fist-sized tuff blocks inserted in a core of opus caementicium.
Initially it consisted of more careful placement of the caementa (rock fragments and small stones mixed with concrete), making the external surface as plain as possible. Later the external surface became plainer still by reducing the amount of concrete and choosing more regular small stones. When the amount of concrete between stones is particularly reduced, it is defined as opus quasi reticulatum. Used from the beginning of the 2nd century BC until the mid-1st century BC, it was later largely superseded by opus reticulatum.
Vitruvius, in De architectura (Ten books on engineering), favours opus incertum, deriding opus reticulatum as more expensive and structurally inferior, since cracks propagate more easily.
See also
Opus quadratum– Roman masonry using parallel courses of squared stone of the same height
Opus mixtum, also known as Opus compositum– Combination of Roman construction techniques
Roman concrete, also known as Opus caementicium– Building material used in ancient Rome
A brick is a type of construction material used to build walls, pavements and other elements in masonry construction. Properly, the term brick denotes a unit primarily composed of clay, but is now also used informally to denote units made of other materials or other chemically cured construction blocks. Bricks can be joined using mortar, adhesives or by interlocking. Bricks are usually produced at brickworks in numerous classes, types, materials, and sizes which vary with region, and are produced in bulk quantities.
Ancient Roman architecture adopted the external language of classical ancient Greek architecture for the purposes of the ancient Romans, but was different from Greek buildings, becoming a new architectural style. The two styles are often considered one body of classical architecture. Roman architecture flourished in the Roman Republic and to an even greater extent under the Empire, when the great majority of surviving buildings were constructed. It used new materials, particularly Roman concrete, and newer technologies such as the arch and the dome to make buildings that were typically strong and well engineered. Large numbers remain in some form across the former empire, sometimes complete and still in use today.
The ancient Romans were the first civilization to build large, permanent bridges. Early Roman bridges used techniques introduced by Etruscan immigrants, but the Romans improved those skills, developing and enhancing methods such as arches and keystones. There were three major types of Roman bridge: wooden, pontoon, and stone. Early Roman bridges were wooden, but by the 2nd century stone was being used. Stone bridges used the arch as their basic structure, and most used concrete, the first use of this material in bridge-building.
The Theatre of Marcellus is an ancient open-air theatre in Rome, Italy, built in the closing years of the Roman Republic. At the theatre, locals and visitors alike were able to watch performances of drama and song. Today its ancient edifice in the rione of Sant'Angelo, Rome, once again provides one of the city's many popular spectacles or tourist sites.
Vulci or Volci was a rich Etruscan city in what is now northern Lazio, central Italy.
Opus reticulatum is a facing used for concrete walls in Roman architecture from about the first century BCE to the early first century CE. They were built using small pyramid shaped tuff, a volcanic stone embedded into a concrete core. Reticulate work was also combined with a multitude of other building materials to provide polychrome colouring and other facings to form new techniques. Opus reticulatum was generally used in central and southern Italy with the exception being its rare appearance in Africa and Jericho. This was because of tuff's wider availability and ease of local transport in central Italy and Campania compared to other regions.
Opus sectile is a form of pietra dura popularized in the ancient and medieval Roman world where materials were cut and inlaid into walls and floors to make a picture or pattern. Common materials were marble, mother of pearl, and glass. The materials were cut in thin pieces, polished, then trimmed further according to a chosen pattern. Unlike tessellated mosaic techniques, where the placement of very small uniformly sized pieces forms a picture, opus sectile pieces are much larger and can be shaped to define large parts of the design.
The Piscina Mirabilis is an Ancient Roman cistern on the Bacoli hill at the western end of the Gulf of Naples, southern Italy. It ranks as one of the largest ancient cisterns built by the ancient Romans, compared to the largest Roman reservoir, the Yerebatan Sarayi in Istanbul.
Opus quadratum is an ancient Roman construction technique, in which squared blocks of stone of the same height were set in parallel courses, most often without the use of mortar. The Latin author Vitruvius describes the technique.
Opus latericium is an ancient Roman construction technique in which course-laid brickwork is used to face a core of opus caementicium.
Opus spicatum, literally "spiked work," is a type of masonry construction used in Roman and medieval times. It consists of bricks, tiles or cut stone laid in a herringbone pattern.
Opus vittatum, also called opus listatum, was an ancient Roman construction technique introduced at the beginning of the fourth century, made by parallel horizontal courses of tuff blocks alternated with bricks.
Opus craticum or craticii is an ancient Roman construction technique described by Vitruvius in his books De architectura as wattlework which is plastered over. It is often employed to construct partition walls and floors. Vitruvius disparaged this building technique as a grave fire risk, likely to have cracked plaster, and not durable. Surviving examples were found in the archaeological excavations at Pompeii and more so at Herculaneum, buried by the eruption of Mount Vesuvius in 79 AD and excavated beginning in 1929.
Opus mixtum, or opus vagecum and opus compositum, was an ancient Roman construction technique. It can consist in a mix of opus reticulatum and at the angles and the sides of opus latericium. It can also consist of opus vittatum and opus testaceum. Opus mixtum was also used from the 4th to 6th centuries AD.
Rubble masonry or rubble stone is rough, uneven building stone not laid in regular courses. It may fill the core of a wall which is faced with unit masonry such as brick or ashlar. Some medieval cathedral walls have outer shells of ashlar with an inner backfill of mortarless rubble and dirt.
The Roman architectural revolution, also known as the concrete revolution, is the name sometimes given to the widespread use in Roman architecture of the previously little-used architectural forms of the arch, vault, and dome. For the first time in history, their potential was fully exploited in the construction of a wide range of civil engineering structures, public buildings, and military facilities. These included amphitheaters, aqueducts, baths, bridges, circuses, dams, roads, and temples.
Opus africanum is a form of ashlar masonry used in Carthaginian and ancient Roman architecture, characterized by pillars of vertical blocks of stone alternating with horizontal blocks, filled in with smaller blocks in between.
The Aqua Anio Vetus was an ancient Roman aqueduct, and the second oldest after the Aqua Appia.
In architecture, the latin term opus ("work") is a word that generically indicates various techniques of constructing buildings that were in use in ancient Rome. Usually, the word opus is not used alone in building descriptions, but is paired with specific attributes whose purpose is to show precisely the building technique that was used.
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