Architect peter salter records the english innovation of the fan vault, a pragmatic and romantic alternative to the gothic arch that has challenged his thoughts on contemporary skins
The fan vault is an English innovation not seen in the churches of continental Europe. It developed in the 14th century as a shell form that was inserted into existing Norman or Romanesque structures as an alternative to the Gothic arch, whose loading paths required either pinnacles or flying buttresses (or both). Whereas the French and others pursued the Gothic rigorously and sought to build an integrated language between structure, space and envelope, the English took a more pragmatic approach.
Instead of razing the churches completed after the Norman Conquest and rebuilding in the Gothic, they modified and added to these existing structures to create fan vaults as a decorative layer within. In today’s world we are used to the architectural envelope being built up as a series of layers; the development of the fan vault is therefore not only of historical interest, but also as a very early precursor from a bygone masonry era.
The architectural idea of the Gothic vault - using the arched geometry of ribs and spandrels to achieve a soaring lightness in which the body of the church is both a religious idea and structural enclosure, as well as a masonry skin - was never achieved in the fan vault. The fan vault is seen as an installed secondary skin whereby its beauty is differently understood to that of the ambition of the Gothic vault. The fan vault as a critically slim conoid skin distributes self loads throughout its rotated curved surface as structure, and is without the concentrated load patterns of ribbed geometry found in Gothic architecture.
The fan vault as an installed structure resulted from the intermittent financing of staged building programmes, particularly the restorations and adaptions of the much earlier Norman stone church building programmes that after the Conquest replaced the timber framed structures of the Anglo Saxons. There was a lack of the institutional ambition demonstrated in the Gothic wish to link a newly developed structure with a renewed establishment of faith. The fan vault sheltered religious belief and benefaction on a local scale and required a separate roof to shed the rain.
Freed from the geometry of a ribbed vault, the fan vault was able to take on the decoration of the time, particularly designs based on the ogee curve and what medieval historian John Harvey named reticulated tracery: each block of the rotated arched surface being cut to receive the dendritic patterns associated with nature. Regarded by architectural author Walter Leedy as a ‘proto-fan’, the tomb canopy of Hugh Lord Despenser (1350) in Tewkesbury Abbey is an early example of the composition of conoid forms and what was to become the geometry of the fan vault.
It does not look to the Gothic vault for its antecedence, but rather seeks a way of resolving the tiered pointed arches and cusped work of the canopy sheltering the pair of reclining figures below. Built in stone, it follows the timber stall carving of Gloucester Cathedral. It is not a true fan vault in its construction but is made up of a series of stepped and cantilevered blocks cut on the underside to form the appearance of vaulting. This soffit forms a series of conoid surfaces, which descend down to columns that separate the figures and describe the volume of the tomb. It could be read as a reliquary or tabernacle; a furniture-scale piece or a church in miniature. Vestiges of colour remain, indicating a painted pattern of ribs articulating the conoids.
Although the Gothic vault, and to a large extent the fan vault, uses a stone vocabulary, the use of timber like that of the stalls at Gloucester reflects a more intimate scale and delicacy of construction. Very often the miniaturisation of architectural form found in tombs, choir stalls and tabernacles results in rich and decorated objects of beauty associated with religious institutions and curiously with vows of poverty. The installation of such pieces within buildings constructed by earlier religious orders, which define beauty through finely crafted architecture with a limited material pallet, increased the sense of their being religious furniture pieces, spatially finer and distinctively crafted as though an architecture within an architecture - like that of a Russian doll or a Fabergé egg.
The Hugh Lord Despenser tomb, the Founders Chapel and the Trinity Chapel are arranged between the Gothic arches of the chancel at Tewkesbury Abbey, with the effigies and altars orientated to the high altar, as a necklace of chapels. The Trinity Chapel (1357) and the later Founders Chapel (1397) are both chantry chapels - church spaces dedicated to masses for the founder’s soul - a common feature of the 14th century, presumably as a response to the Black Death that advanced through Britain and in particular through the gates of Gloucester between 1348 and 1350.
Trinity Chapel is regarded as the first structural fan vault to be made of jointed masonry following the conoid form. At 1.66m wide it is regarded by Walter Leedy as a ‘toy fan vault’. Leedy speculates that these early examples of fan vaults probably influenced the construction of the wooden tester for the later tomb of Edward III, constructed by master carpenter Hugh Herland.
Experimentation with its spanning capabilities, stylistic and load-bearing qualities was developed through different commissions, sometimes constructed in timber and at other times in stone. It was an evolutionary process, probably initiated by royal masons and carpenters and taken to workshops where local craftsmen under the supervision of the master mason developed the form.
Such workshops located in the West Country and particularly in the yards associated with Tewkesbury, Hereford and Gloucester, were responsible for developing the form. A tracing floor has been found in the north porch of Wells Cathedral and there are reputed to be traces of a similar floor at Hereford Cathedral. These floors were made with a plaster finish in order to scribe full size the shapes and carvings of the stone block to be worked.
If the Trinity Chapel is seen as an ideological piece, an architecture as furniture, viewed through perimeter grillage except during the chantry ceremony, then the fan vaulted cloister of Gloucester Cathedral (built between 1381 and 1412) is the first manifestation of fan-vaulted architecture within which to perambulate and experience its spatial quality. The five bays on the east sidewalk adjacent to the church entrance were the first to be made, presumably almost as a prototype and under strict supervision. The remaining bays completed later used a standardised jointing system that could not adapt to the vagaries of the earlier foundations. Warping is visible in the tracery, accommodating differences in the masonry shell as it takes up the inconsistencies of bay dimensions.
The fan vaults of Gloucester cloister were constructed from centring bays based upon earlier Norman foundations. From a single stone pilaster a ring of jointed masonry was laid in line with the curvature of the conoid. Subsequent rings were corbelled following this arch until the curved blocks met at the apex. Each block had been cut to a three-dimensional geometry following the circumference of the coursing and the arch spring. At the apex of the meeting of four conoids infill blocks lying almost flat to the geometric surface act as key stones to lock in the corbelled conoid form.
Because the cloister construction has to span between other existing structures and external buttresses around the cloister, the conoid pocket - that is the space behind the masonry shell - is left open to the void between the fan vault masonry and the lean-to roof above. In other circumstances the conoid pocket is filled with mortar to increase the sectional depth of the conoid and to bring the line of forces within the structure of the fan vault.
In Gothic architecture the re-aligning of forces travelling down the ribs and spandrels of the vault is achieved by flying buttresses or a pinnacle weight above the springing point of the arch. Unlike the Gothic vault, where the expression of forces is described by ribs and spandrels, the blocks of the fan vault conoid are free to be carved to the reticulated design of the enclosure.
The Gloucester cloister follows an almost dendritic pattern of cusped and scribed ribs, as though a tree design. Because the rib carving is free from structural expression, the depth of carving and light modulation gives the space spectacular quality. Due to the circumstances in which the fan vault evolved it is often seen as an adaption or as an addition to the church, either as a side chapel or a porch, uncertain as to whether it is an ostentatious addition or part of a quiet, well-crafted country churchyard. When seen as an enlarged structure, such as the tour de force at Sherborne, Bath or Westminster Abbey’s Henry VII Chapel, it still retains this fine-scaled furniture-like quality. Although Harvey regarded the fan vault as somewhat inferior to the Gothic vault, its installed shell formation offers
much as a way of thinking about contemporary skins.