Pendentives & Squinches in Architecture

Instructor: Stephanie Przybylek

Stephanie has taught studio art and art history classes to audiences of all ages. She holds a master's degree in Art History.

How do you add a dome to a building? Can you fit a round space on top of a square one? In this lesson, we will learn about pendentives and squinches and their uses in architecture.

What are Pendentives and Squinches?

How do you fit a round space on top of a square one? This is the question architects had to wrestle with when trying to figure out how to build domes. Ancient architects came up with two solutions that came to be known as pendentives and squinches.

Pendentives and squinches are architectural supports that bridge the difference between a square room and the curved dome that rises above it. Both developed in the ancient world and although in some cases they look similar, they're very different. We'll discuss the squinch first, because it probably developed a bit earlier than the pendentive. It's the more basic of the two solutions.

How a Squinch Works

A squinch is a wedge that fits on the top corners of a square space. At the point where the dome's bottom edge meets the room's upper horizontal edges, four triangular-like wedges (often similar to a small bridge or arch) are placed in the corners.

Drawing of a squinch showing how it is used as an arch support
drawing of a squinch

Think of squinches as diagonal supports constructed across corners. The four squinches turn the square into an octagon, which enables a dome to rest on top of it. The squinch developed in the Middle East and ancient Rome around the 5th century AD, and it was often used in early Islamic and Byzantine architecture. It solved the problem of supporting the dome but tended to have a blocky, chunky appearance.

Example of a corner squinch from a tomb in New Delhi, India
squinch in an Idian tomb

How a Pendentive Works

A pendentive also supports a dome but it's more complicated, using geometry to create a series of curving and arched supports. Pendentives also developed in the Middle East and Byzantine world. Essentially, a pendentive is a spherical triangle that serves as an arch. Architects used four pendentives on the upper corners of a room, where they arched inward to meet the dome's circular base. One of the earliest examples of pendentives can be found in Hagia Sophia, a structure in Istanbul, Turkey that was built around 537 AD.

Example of a dome with supporting pendentives in Hagia Sophia
Dome with pendentives in Hagia Sofia

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