Voussoir

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Old College, University of Edinburgh courtyard facade detail

Voussoir is an architectural term referring to the wedge-shaped stones that make up an arch or a vault. The voussoirs are placed such that their narrow side is towards the center of the arch, creating a self-supporting structure that distributes the weight of the arch and the load above it down into the supports on either side. This ingenious design allows for the construction of wide and stable openings in walls, and has been a fundamental aspect of architecture since ancient times.

History

The use of voussoirs dates back to ancient civilizations, including the Roman Empire, where they were employed in the construction of monumental structures such as aqueducts, bridges, and, most famously, the Roman Colosseum. The Romans perfected the arch technique, which was later adopted and further developed by subsequent civilizations, notably in Gothic architecture, where pointed arches and ribbed vaults required precisely cut voussoirs.

Design and Function

A key element in the design of an arch is the keystone, the central voussoir at the apex of the arch. The keystone is crucial for the stability of the arch, as it locks the other voussoirs into place, allowing the arch to bear weight. The sides of the arch where it meets its supports are known as the spring points, and the curve formed by the voussoirs is known as the intrados.

In addition to their structural role, voussoirs have also been used decoratively. In many cases, the voussoirs are carved or constructed from materials of contrasting colors or textures to highlight the arch and add visual interest to the structure.

Construction

The construction of an arch using voussoirs requires precise engineering and craftsmanship. Each voussoir must be meticulously cut to fit its specific location in the arch, with the angles of the sides determined by the shape and size of the arch. This requires a detailed understanding of geometry and structural engineering.

In modern construction, voussoirs can be made from a variety of materials, including stone, concrete, and even steel. The principles behind their use, however, remain largely unchanged from ancient times.

Applications

Voussoirs are not only used in the construction of arches but are also a fundamental component in the construction of vaults and domes. In these structures, the voussoirs are arranged in a series of arches that span across a space, creating a self-supporting shell that can cover large areas without the need for internal supports.

See Also

• Arch
• Vault
• Keystone
• Gothic architecture
• Roman architecture