voussoir

architecture

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Last updated

July 15, 2026

Quick Summary

A voussoir is a wedge-shaped block used in the construction of arches and vaults. These precisely cut stones are essential for creating the curved structure of an arch, with the central voussoir being known as the keystone.12

Arches, unlike horizontal beams, can span wider openings and support greater loads because the downward pressure forces the voussoirs together. This design redirects forces outward and downward, creating a thrust that must be supported by massive foundations or buttresses. The Romans extensively used the semicircular arch in bridges and aqueducts, relying on the precision of their stone cutting rather than mortar.2

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bridge
Roman arch bridges
…feature huge arch stones (voussoirs) weighing up to eight tons each. Typical of the best stone bridges, the voussoirs at Alcántara were so accurately shaped that no mortar was needed in the joints. This bridge has remained standing for nearly 2,000 years.
Read More
…feature huge arch stones (voussoirs) weighing up to eight tons each. Typical of the best stone bridges, the voussoirs at Alcántara were so accurately shaped that no mortar was needed in the joints. This bridge has remained standing for nearly 2,000 years.
Read More