Rib vault
A rib vault or ribbed vault is an architectural feature for covering a wide space, such as a church nave, composed of a framework of crossed or diagonal arched ribs. Variations were used in Roman architecture, Byzantine architecture, Islamic architecture, Romanesque architecture, and especially Gothic architecture. Thin stone panels fill the space between the ribs. This greatly reduced the weight and thus the outward thrust of the vault. The ribs transmit the load downward and outward to specific points, usually rows of columns or piers. This feature allowed architects of Gothic cathedrals to make higher and thinner walls and much larger windows.
It is a type of arcuated, or arched, vault in which the severies, or panels in the bays of the vault's underside are separated from one another by ribs which conceal the groins, or the intersections of the panels. Rib vaults are, like groin vaults, formed from two or three intersecting barrel vaults; the ribs conceal the junction of the vaults.
The first rib vaults were built by the ancient Romans in the 2nd century AD. In the medieval period the earliest surviving example in Islamic architecture is at the Mosque–Cathedral of Córdoba in al-Andalus, which predates the earliest Romanesque examples by a century. An alternative to barrel vaults in the naves of churches, rib vaults in 12th century early Gothic architecture began to be used in vaults made with pointed arches, already known in the Romanesque style. In these vaults, as in groin vaults, the weight was directed it to the corners, where piers, columns, or walls could support it. Walls in Gothic buildings were often abutted by flying buttresses. These elements made it possible to construct buildings with much higher and thinner walls than before, with immense bays, and larger stained glass windows filling the structure with light.
Cross vaults are constructed of narrow, arched ribs that diagonally cross the area to be covered. The severies can be filled with small pieces of masonry, eliminating much of the massive weight of barrel vaults. These rib vaults could also more efficiently cover large rectangular areas. Thanks to the pointed arch employed in Gothic architecture, builders could raise or lower the arches so they would have the same height for a short span or a long span, something not possible with round arches. Pointed arches also made two intersecting vaults of the same height but different widths easier to construct.
Early history
The Romans used an early version of the rib vault to strengthen groin vaults. In these Roman vaults, the brick ribs were embedded into the concrete of the vault. This was different from the later Gothic vaults, where the ribs were separate from the infilling of the panels, which gave the Gothic vaults flexibility and thus greater strength. The Romans also used these embedded ribs concealed within the structure to strengthen the concrete surface of domes, such as the Pantheon.Rib vaults were not common in masonry buildings in Byzantine architecture, but four ribbed vaults were built by the Hosios Loukas monastery in Byzantine Greece after 1000 AD, and at the now ruined town Çanlı Kilise in Byzantine Cappadocia several groin vaults in medieval churches are equipped with ribs. A number of other rib vaults were built in Greece under the Frankokratia after the Fourth Crusade. Varieties of early rib vaults were known in Lombard, Armenian, Persian, and Islamic architecture.
Cross vaults
Roman architecture
The first known example of ladder ribs used on cross vaults is the one documented in the Villa of the Sette Bassi in Rome, dating from the mid-second century AD.File:Rome rib cross vault.jpg|thumb|Rib vault from Villa Sette Bassi, Rome
Islamic architecture
In the Moorish architecture of Spain, Islamic architects used these ribbed vaults more visibly. One notable example is found in the Great Mosque of Córdoba, which was begun in the 9th century and extended between 922 and 965 by Al-Hakam II. The Chapel of Villaviciosa, as this part of the mosque became known when it was converted to a Roman Catholic church in the 13th century, has a dome which rests upon ribs and pendentives. At each vertex of the square is the intersection with another arch, such that each intersection is the junction of three arches. At each corner is a further miniature cross-vault dome. In the other domes of the 10th century reconstruction of the Great Mosque, the ribs intersect one another off-centre, forming an eight-pointed star in the centre which is topped by a pendentive dome.The crossed-arch vaults of the mosque-cathedral of Córdoba served as models for later mosque buildings in the Islamic West, including al-Andalus and the Maghreb. At around 1000 AD, the Mezquita de Bab al Mardum in Toledo was constructed with a similar, eight-ribbed vault. The dome is supported both by the ribs and by pendentives that transmit its weight to the walls below. Similar vaults are also seen in the mosque building of the Aljafería of Zaragoza. The architectural form of the ribbed vault was further developed in the Maghreb: the central dome of the Great Mosque of Tlemcen, a work of the Almoravids built in 1082, has twelve slender ribs, the shell between the ribs is filled with filigree stucco work. The Almohads also expanded its use to military structures, as exemplified in the Atalaya Castle in Villena.
Romanesque architecture
The rib vault was developed further in northern Europe in the 11th century, as builders sought a way to construct larger and larger stone vaults to replace the wooden roofs of Romanesque churches, which were frequently destroyed by fire. Romanesque cathedrals and churches usually used the barrel vault, with rounded arches, and the groin vault, used when two vaults met at a right angle to cover the nave. The weight of the vaults pressed down directly onto the walls below, requiring thicker walls and smaller windows.Saint-Philibert de Tournus has exceptional Romanesque vaults, built between 1008 and 1050. The nave and chapel have parallel traverse tunnel vaults, while the aisles of both interiors are groin-vaulted.
Speyer Cathedral in Germany is the largest of all existing Romanesque churches in Europe, and has good examples of Romanesque barrel vaults and groin vaults in the nave. The groin vaults were built in 1060, and but had to be reinforced in 1090–1103 with a traverse arch between each arch.
The Kingdom of England and the Duchy of Normandy became centres of architectural innovation in the late 11th century. Even before the Norman Conquest in 1066, King Edward the Confessor of England had introduced Romanesque features to Westminster Abbey. William the Conqueror constructed the domes of the Abbey of Saint-Étienne, Caen with a kind of crossed rib vault, a star vault, in its central lantern. The Abbaye-aux-Dames also in Caen, was roofed with two large bays of stone groin vaults in the 1080s, one of the earliest uses in Europe of a groin vault to cover such a wide span.
Transition to Gothic architecture
Construction of the new church at Durham Cathedral began in 1093 under the direction of its Norman bishop, William de St-Calais. It was originally intended to build the cathedral entirely with rounded-arch groin vaults, but as work continued on the nave the Norman builders experimented with pointed arches, which directed the weight outward and downwards. The space between the ribs was filled with severies made of small pieces of stone. At its corners the weight was supported by colonettes which transferred it downwards to alternating columns and piers below rather than to the walls. Since the panels are relatively thin, these rib vaults are lighter than the earlier barrel and groin vaults so the walls could be higher and could have larger windows.The work began at the east end of Durham Cathedral; the vaults over the aisles were complete in 1096, and over the choir by 1107. The nave vaults, with pointed arches, were begun in about 1130. Thanks to the pointed arches, the upper level of the clerestory seemed to merge into the roof in a unified whole. The Durham experiment, however, quickly ran into problems. The vault panels in the chancel were made of plastered rubble, and were heavier than expected, and began to crack, and had to be replaced in 1235. In the meanwhile, experimentation in pointed rib vaults moved to France, where thinner and lighter panels were made of small cut pieces of stone, rather than rubble.
The Romanesque Lessay Abbey in Normandy added early Gothic rib vaults in the choir in about 1098. which covered portions of the choir and nave. It was destroyed in World War II but rebuilt. The dome of the Romanesque Church of the Holy Sepulchre, Cambridge in England, begun in 1130, has ribs in the dome, though the dome rests upon pendentives, and the ribs were largely decorative. The Romanesque Cefalù Cathedral in the Norman Kingdom of Sicily, begun in 1131, has a Gothic rib vault.
The transition from Romanesque to Gothic can also be seen in the nave of Fontenay Abbey church, where the round arches of the barrel vaults have been replaced by vaults with slightly pointed arches.
Other variations of rib vaults, usually with rounded arches, appeared in Lombardy in the Basilica of Sant'Ambrogio, Milan, at the end of the 11th century, and in Southwest France at Moissac Abbey. These were usually groin vaults, composed by joining two barrel vaults at right angles. Other types of vaults were decorative, such as the star vaults used to decorate the lantern tower on the roof of Caen Cathedral and Laon Cathedral, or the ribs on the interior of the dome of the Round Church in Cambridge.
Sexpartite vaulting
In sexpartite vaulting, each bay was divided by thin stone ribs into six compartments. The intermediate ribs diagonally crossing the vault formed a pointed arch, and there was an additional intermediate pointed arch, which crossed from side to side. Since the ribs carried the weight, the panels of the vaults were made of small pieces of stone, and were much lighter than traditional barrel vaults. The ribs transmitted the weight outwards and downwards through slender columns to the piers on the lower level. The weight was not distributed equally; the additional weight of the diagonal traverse arches was supported by massive piers, while the intermediate crossing arch was supported by simple columns. Since the weight of the vaults was carried by the columns and piers, not the walls, the walls could be thinner and higher, and they could be filled with larger stained glass windows.The sexpartite vault appeared almost simultaneously in England and France. The first cathedral to use sexpartite vaults was Durham Cathedral, begun in 1093. Durham was originally intended to be built with more traditional groin vaults. The vaults over the aisles were completed in 1096, those over the choir in 1107, these over the north transept and 1110. The traverse vaults of the nave, however, the arches over the south transept and nave, begun 1130, were given pointed arches. Early examples of sexpartite rib vaults are found at the Abbaye-aux-Hommes and Abbaye-aux-Dames at Caen. It then appeared in Noyon Cathedral ; the square Gothic porch of the Romanesque church of Vézelay Abbey in France ; Sens Cathedral ; the choir of the Abbey of Saint-Denis ; Notre-Dame de Paris ; Bourges Cathedral; and Laon Cathedral. Ribbed vaults were built by William the Englishman at Canterbury Cathedral and in St Faith's Chapel in Westminster Abbey.