Voussoir

A voussoir (UK: /ˈvuːˈswɑː/; US: /vuˈswɑːr/) is a wedge-shaped element, typically a stone, which is used in building an arch or vault.^[1][2][3]

William Henry Playfair, University of Edinburgh: bevelled edges of each stone block emphasise the voussoirs, which have a curved base and together form a semi-circle at the top of each arch.

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 rely on the balance of one another to stay in place. In addition, there are different types of voussoirs that include joggled voussoirs. The joggled voussoirs were originally developed in Roman architecture, in order to strengthen the structure, before being implemented into Islamic architecture.^[4] The shape of the wedged pieces have a curved structure to them, almost resembling puzzle pieces, that fit together and lock into place. Joggled voussoirs were adopted by Islamic architects in order to strengthen the arches, as well as during bridge construction of the time. This allowed the structures to sway with the movements of potential earthquakes, and move back to its original position.^[4]

Although each unit in an arch or vault is a voussoir, two units are of distinct functional importance: the springer the keystone. The springer is the lowest voussoir on each side, located where the curve of the arch springs from the vertical support or abutment of the wall or pier.^[1][2] The keystone is the centre 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 in Mannerist arches of the 16th century, beginning with the works of Giulio Romano, who also began the fashion for using voussoirs above rectangular openings, rather than a lintel (Palazzo Stati Maccarani, Rome, circa 1522). With the addition of taller keystones, it adds a sense of stability, allowing the arches to be constructed easier 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.^[6]

Each wedge-shaped voussoir turns 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 the buttresses, piers or abutments. Voussoir arches distribute weight efficiently, and take maximum advantage of the compressive strength of stone, as in an arch bridge.^{[citation needed]} The outer boundary of a voussoir forms an extrados, internal - an intrados (soffit).^[7][2]

In Visigothic, Moorish, and Damascene architectural traditions, the voussoirs are often in alternating colours (ablaq), which is also found sometimes in Romanesque 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]

Examples of Voussoirs:

Inside, upward view of the Dome of the Rock highlighting colorful and detailed voussoirs.

The Dome 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.^[9]

Inside view of colorful, two tiered voussoirs located in the Great Mosque of Córdoba.

The Great Mosque of Córdoba also contains prominent voussoirs displayed in arch form, utilizing the Cordovan 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.^[10]

Etymology

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

See also

• Glossary of architecture