Squinch

In architecture, a squinch is a structural element used to support the base of a circular or octagonal dome that surmounts a square-plan chamber. 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); or a small half-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.

Squinches originated in the Sassanid 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. Georgia and Armenia 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. An alternative approach to the structural problem of translating square space to round superstructure is the pendentive, much used in late Roman Empire and Byzantine architecture. Domes built in the Roman-influenced world utilised separately-evolved construction methods.

History

Western Asia

The dome chamber in the Palace of Ardashir, the Sassanid king, in Firuzabad, Iran, is the earliest surviving example of the use of the squinch. After the rise of Islam, it remained a feature of Islamic architecture, especially in Iran, and was often covered by corbelled stalactite-like structures known as muqarnas. It was used in Western Asia and the Middle East, and in eastern Romanesque architecture, although pendentives are more common in Byzantine architecture. The Hagia Sophia features both squinches and pendentives, in combination.

Western Europe

The feature spread to the Romanesque architecture of western Europe. The earliest squinch still extant in Europe is the 5th-century Baptistery of San Giovanni in Fonte, Naples. . A later example is the 12th-century Norman church of San Cataldo, Palermo, in Sicily. This has three domes, each supported by four doubled squinches.

Etymology

The word may possibly originate, the ''Oxford English Dictionary'' suggests, from the French word ''escoinson'', meaning "from an angle", which became the English word "scuncheon" and then "scunch".

See also

* History of early and simple domes
* History of Persian domes
* History of Roman and Byzantine domes
* Splayed arch, an arch with conical intrados

References

Further reading

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External links

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Domes
Arches and vaults
Architectural elements
Islamic architectural elements