Pediments are a form of gable in classical architecture, usually of a triangular shape. Pediments are placed above the horizontal structure of the cornice (an elaborated lintel), or entablature if supported by columns. In ancient architecture, a wide and low triangular pediment (the side angles 12.5° to 16°) typically formed the top element of the portico of a Greek temple, a style continued in Roman temples. But large pediments were rare on other types of building before Renaissance architecture. For symmetric designs, it provides a center point and is often used to add grandness to entrances.
The cornice continues round the top of the pediment, as well as below it. The tympanum is the triangular area within the pediment, which is often decorated with a pedimental sculpture which may be freestanding or a relief sculpture. The tympanum may hold an inscription, or in modern times, a clock face.
Pediments are found in ancient Greek architecture as early as 580 BC, in the archaic Temple of Artemis, Corfu, which was probably one of the first. Variations of the pediment occur in later architectural styles such as Classical, Neoclassical and Baroque.
The pediment is found in classical Greek temples, Etruscan, Roman, Renaissance, Baroque, Rococo, Neoclassical and Beaux-Arts architecture. Greek temples, normally rectangular in plan, generally had a pediment at each end, but Roman temples, and subsequent revivals, often had only one, in both cases across the whole width of the main front or facade. The rear of the typical Roman temple was a blank wall, usually without columns, but often a full pediment above. This effectively divorced the pediment from the columns beneath it in the original temple front ensemble, and thereafter it was no longer consider necessary for a pediment to be above columns. The most famous example of the Greek scheme is the Parthenon, with two tympanums filled with large groups of sculpted figures. An extreme but very influential example of the Roman style is the Pantheon, Rome, where a portico with pediment fronts a circular temple.
In ancient Rome, the Renaissance, and later architectural revivals, small pediments are a non-structural element over windows, doors and aediculae, protecting windows and openings from rain, as well as being decorative. From the 5th century pediments also might appear on tombs and later non-architectural objects such as sarcophagi.
In Carolingian and Romanesque architecture pediments tended towards the equilateral triangle, and the enclosing cornice has little emphasis; they are often merely gable ends with some ornament. In Gothic architecture pediments with a much more acute angle at the top were used, especially over doorways and windows, but while the rising sides of the cornice is elaborate, the horizontal bottom element was typically not very distinct. Often there is a pointed arch underneath, and no bottom element at all. "Pediment" is typically not used for these; they are often called a "canopy". From the Renaissance onwards, some pediments no longer fitted the steeply pitched roofs and became freestanding, sometimes sloping in the opposite direction to the roof behind.
When classical-style low triangular pediments returned in Italian Renaissance architecture, they were initially mostly used to top a relatively flat facade, with engaged elements rather than freestanding porticos supported by columns. Leon Battista Alberti used them in this way in his churches: the Tempio Malatestiano (1450s, incomplete), Santa Maria Novella (to 1470), San Sebastiano in Mantua (unfinished by the 1470s), Sant'Andrea, Mantua (begun 1472), and Pienza Cathedral c. 1460), where the design was probably his.
In most of these Alberti followed classical precedent by having the pediment occupy the whole width of the facade, or at least that part that projects outwards. Santa Maria Novella and Sant'Agostino, Rome (1483, by Giacomo di Pietrasanta) were early examples of what was to become a very common scheme, where the pediment at the top of the facade was much less wide, forming a third zone above a middle zone that transitioned the width from that of the bottom. As in Gothic architecture, this often reflected the shapes of the roofs behind, where the nave was higher than the side-aisles.
A variant is the "segmental" or "arch" pediment, where the normal angular slopes of the cornice are replaced by one in the form of a segment of a circle, in the manner of a depressed arch. Both traditional and segmental pediments have "broken" and "open" forms. In the broken pediment the raking cornice is left open at the apex. The open pediment is open along the base – often " sculpture, "tondo" paintings, mirrors or windows. These forms were adopted in Mannerist architecture, and applied to furniture designed by Thomas Chippendale. The terms "open pediment" and "broken pediment" are often used interchangeably. Another variant is the swan's neck pediment and is a refinement of a broken pediment with two "S"-shaped profiles resembling a swan's neck. Non-triangular variations of pediments are usually found over doors, windows, and porches.
West front of the Temple of Athena, Paestum, c. 500 BC
Pediment of the Mihai Zisman House (Calea Călărașilor no. 44), Bucharest, by architect Soru, 1920