Avoussoir (UK:/ˈvuːˈswɑː/;US:/vuˈswɑːr/) is a wedge-shaped element, typically a stone, which is used in building anarch orvault.^[1][2][3]

Each voussoir is formed in a specific way to fit within the arch or vault created. Normally, different colored stones are shaped to fit together in a curved way that relies on the balance of each other to stay in place. The shaping of the individual wedge pieces varies depending on the type of arch being constructed—round, pointed, horseshoe, multifoil (which require voussoirs to be cut at different angles), and joggled.Joggled voussoirs were originally developed in Roman architecture to strengthen the structure, before being implemented inIslamic architecture.^[4] The wedged pieces have a curved shape, almost resembling puzzle pieces that fit together and lock into place. Joggled voussoirs were adopted by Islamic architects in order to strengthen arches and bridges by allowing them to sway with the movements of potential earthquakes and move back to their original position.^[4]

Although each unit in an arch or vault is a voussoir, there is distinct functional importance in two positions.Springers are the lowest voussoir on each side, located where the curve of the arch springs from thevertical support orabutment of the wall orpier.^[1][2] Springers often require precise shaping to control the direction of thrust and ensure successful transfer of weight to the supports below. Thekeystone is the center stone or masonry unit at the apex of an arch that locks the voussoirs in place.

The keystone is often decorated or enlarged. An enlarged and sometimes slightly dropped keystone is often found inMannerist arches of the 16th century, beginning with the works ofGiulio Romano, who also began the fashion for using voussoirs above rectangular openings, rather than alintel (Palazzo Stati Maccarani, Rome, circa 1522). Taller keystones add a sense of stability, allowing the arches to be constructed more easily, with the keystone being dropped into the center of the arch.^[5] This central point on the arch balances the structure, but also starts an important identifying factor of Islam architecture and artistry. Many times throughout history, keystones were carved decoratively to highlight the central piece, usually with vegetal designs or inscriptions. In many architectural traditions, the keystone became a location for ornamental carving because of its visually prominent position.^[6]

Each wedge-shaped voussoirturns aside the thrust of the mass above, transferring it from stone to stone to the springer's bottom face (impost), which is horizontal and passes the thrust on to thebuttresses,piers orabutments. Voussoir arches distribute weight efficiently, and take maximum advantage of thecompressive strength of stone, as in anarch bridge.^[2] The outer boundary of a voussoir forms anextrados, internal - anintrados (soffit).^[7][2]

InVisigothic,Moorish, and Damascene architectural traditions, the voussoirs are often in alternating colours (ablaq), which is also found sometimes inRomanesque architecture. Leading into the Umayyad period, the alternating colors were used for decorative purposes, but also based on the material available at the time (brick and stone). With this, the alternating red and white stones created an association to Islamic art and ‘Abd al-Rahman I himself, as well as his followers during the Umayyad period.^[8]

Voussoirs are present in multiple mosques, and serve not only as an architectural structure, but as a symbol of the entry into a theological place of worship. The arched entryways on the exterior of a mosque were believed to be a portal; leaving the outside world and going into a divine, holy space. Not only was walking under an arch a physical act, it was a spiritual transition, guiding the worshipper into divine focus.^[9]

TheDome of the Rock displays voussoirs creating the arches inside the monument. The green and white colored voussoirs exemplify the Umayyad style by continuing a sense of divineness, in comparison with using mosaics, inscriptions, and carvings. In doing so, concepts of vases and vegetal designs, paired with the updated architecture of the voussoirs, establish a sense of power during the time.^[10]

TheGreat Mosque of Córdoba also contains prominent voussoirs displayed in arch form, utilizing the Cordoban Caliphate arch concept. The arches are in sets of two, lined in rows and columns. In regards to the Umayyad period, these voussoirs focused on three main components: the red and white coloring, textured wedge shapes, and intricate detail. The architectural form also changed during the time to make the stones wider and more radial. Using different colored voussoirs helps highlight the shape of the arch and makes it easier to see how the pieces fit together.^[11]

The word is astonemason's term borrowed inMiddle English from French verbs connoting a "turn" (OED).^[3]

• Glossary of architecture

Wikimedia Commons has media related toVoussoirs.

• Photo repertory of voussoirs — at www.OntarioArchitecture.com

• Arches and vaults
• Masonry
• Ornaments (architecture)
• Architectural elements
• Architectural history
• Moorish architecture
• Islamic architectural elements

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