Inarchitecture, asquinch is a structural element used to support the base of a circular or octagonaldome that surmounts a square-plan chamber.[1] Squinches are placed to diagonally span each of the upper internal corners (vertices) where the walls meet. Constructed from masonry, they have several forms, including a graduated series of stepped arches; a hollow, open half-cone (like half of a funnel laid horizontally, also called atrumpet arch[2]); or a smallhalf-dome niche. They are designed to evenly spread the load of a dome across the intersecting walls on which it rests, thus avoiding concentrating higher structural stress on smaller load-bearing areas. By bridging corners, they also visually transition an angular space to a round or near-circular zone.[3]
Squinches originated in theSassanid Empire of Ancient Persia, remaining in use across Central and West Asia into modern times. From its pre-Islamic origin, it developed into an influential structure for Islamic architecture.[4][3][5]Georgia andArmenia also inherited the form from the Sassanids, where squinches were widely employed in buildings of all kinds. They are heavily featured in surviving or ruined medieval Christian churches of the region.[6] An alternative approach to the structural problem of translating square space to round superstructure is thependentive, much used in late Roman Empire and Byzantine architecture.[7] Domes built in the Roman-influenced world utilised separately-evolved construction methods.[5][8]
The dome chamber in thePalace of Ardashir, the Sassanid king, inFiruzabad, Iran, is the earliest surviving example of the use of the squinch.[8][9] After the rise of Islam, it remained a feature ofIslamic architecture, especially inIran, and was often covered bycorbelled stalactite-like structures known asmuqarnas. It was used inWestern Asia and theMiddle East, and in easternRomanesque architecture, although pendentives are more common in Byzantine architecture. TheHagia Sophia features both squinches and pendentives, in combination.
The feature spread to the Romanesque architecture of western Europe. The earliest squinch still extant in Europe is the 5th-centuryBaptistery of San Giovanni in Fonte, Naples.[10] A later example is the 12th-century Normanchurch of San Cataldo, Palermo, in Sicily. This has three domes, each supported by four doubled squinches.
The word may possibly originate, theOxford English Dictionary suggests, from the French wordescoinson, meaning "from an angle", which became the English word "scuncheon" and then "scunch".[11]
... the squinch was the earliest method employed in Armenia; and its appearance in a domed building over a square plan as far east as Chinese Turkestan (Turfan), which dates from the eighth century at latest, supports [the] ... contention that it is an indigenous Asiatic invention, employed from the first in the domed Iranian dwellinghouse, which is still erected in almost its primitive form to-day.ISBN 978-0-87817-135-4.
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