BUTTRESS.—Generic designation for a masonry structure intended to counterbalance the thrusts in vaulted architectural structures. Probably originating in Persian architecture (the oldest example being the palace of Fauruz Abid, perhaps from the 4th century B.C.), buttresses were also known to the Romans, who adopted them in thermal buildings (the so-called temple of Minerva Medica and the Baths of Diocletian, where they take the form of towers).
In the Ravenna churches with a central plan (S. Vitale), buttresses appear as angular spurs. But the first basilical building in which they were adopted is presumably S. Babila in Milan (late 10th century), supporting the double arches that form the framework of the barrel vault. It should be noted, however, that attempts in this direction had already been made in the 9th century in some churches near Oviedo in Asturias.
Another important example from the 10th century is the church of St-Remi at Reims, France, where they support the coverings of both the central nave and the side aisles, thus constituting a double order of load-bearing structures.
It was only when groin vaults were definitively adopted for covering the naves that the buttress became common in northern Italy and throughout central and western Europe; it was often formed in steps, or ended in columns joined to the cornice, or finally conceived in architectural form, as a pilaster or semicolumn extending the entire height (late 12th century).
In this latter period they were also frequent on façades, to support the thrust of the dividing arches of the naves, especially in Lombard churches, but also in those of Emilia and Normandy.
In Gothic architecture, buttresses sometimes take the form of massive semicylindrical towers extending the full height of the building (S. Francesco di Assisi), or resume the stepped form, but with a more animated profile; a subsequent refinement consisted in separating the function of pier in the lower zone from that of mere loading in the upper part (cathedral of Séez), thus limiting the towers to the height of the springing of the vaults (cathedral of Orvieto).
The fourteenth century also extended sculptural decoration to buttresses, terminating them vertically with pinnacles and statues, a practice that continued in the following century (cathedral of Milan, Certosa di Pavia). Generally, in three-nave Gothic churches, buttresses are associated with flying buttresses, which carry the thrusts of the groin vaults of the central nave above them. Nevertheless, even in the full Quattrocento and until the beginning of the following century, Rome still had buttresses (S. Agostino, S. ma Trinità dei Monti) consisting of solid walls; in the latter century and in the seventeenth century these were resolved far more rationally as great volutes, especially in churches with an elliptical plan (S. Giacomo in Augusta, S. Andrea al Quirinale, S. ma Annunziata di Parma, S. Maria della Salute in Venice), while the eighteenth century adopted sturdy towers for the same purpose (SS. Celso e Giuliano in Rome, the sanctuary of Vicoforte).