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Squinches and Pendentives in Architecture
The Romans were the first to truly master arched construction. A dome construction either demanded that the supporting structure is round, such as in Rome’s Pantheon, or are supported on a square base by using a squinch or a pendentive.
The squinch is the simpler of the two. It was developed in the Middle East and ancient Rome around the 5th century AD was often used in early Islamic and Byzantine architecture.
Squinch: A small arch on the inside corner of the square base to connect the dome to the base and transfer its load to the corners.
Squinch: Concept and construction
Straight walls are erected on a square base, a dome is placed on the top of these four walls. This means that the load is transferred from the points the dome meets the walls i.e. the centre of the wall. A heavy structure like dome needs uniform weight distribution hence the load must be transferred through the corners of the square as well. The squinch is achieved by building a short bridge across each corner of a square to transform the base of the dome into an octagon. This can either be achieved by a system of corbelling or by constructing a small arch.
Pendentives: A curved triangle that connect the space between the arches and walls.
Pendentives: Concept and construction
Though squinches solved the problem of supporting the dome they the tended to have a blocky-chunky appearance, hence a much more elegant solution- pendentive was developed by the Byzantines. It is simpler in appearance but more complex in its geometry. Architects used four pendentives on the upper corners of a room, where they arched inward to meet the dome’s circular base. These triangles looked like a triangular sector cut from a sphere
