Gothic Vaulting; A Structural Analysis
Text from a previous essay submission.Like the majority of shifts in architectural styles, the Gothic was born out of a revolutionary attitude. Architecture tends to shape itself to the culture and social dynamic of the time rather than solely the shelter and efficiency of structure. The Gothic manages to tie in both cultural reform and greater structural efficiency hence making it a revolutionary success.
Saint Denis found at Liberation
First developed in the northern region Île-de-France, Abbot Suger was the pioneer of this world-renowned style. His vision was great, aspiring to redesign one of the most prestigious abbeys of France, the Basilica of Saint-Denis, where he was elected abbot, looking to exceed some of the most influential early Christian architecture, including ‘Hagia Sophia’.
After the completion of the abbey in 1140, his work was met with great criticism. ‘Gothic’ was a derogatory term used to pair the style with the barbaric gothic tribe who wrecked havoc among civilisations in the past. His critics aimed to brand this newfound style as ‘unrefined’ in comparison to Romanesque architecture, which had been long favoured in Europe. This however couldn’t be further from reality, Suger’s design was extremely refined with strong symbolic allusions to biblical scriptures and an immersive atmosphere, transforming the inhabitant into a space of higher spirituality.
Using descriptions of the Temple of Solomon to inspire Suger’s design, the architect managed to evoke a sense of divine energy through certain elements, designing an abbey which both physically and metaphysically brings the inhabitant closer to God. Features including the emphasis on verticality and innovative use of light aid in echoing this motif. One that has remained constant throughout the continuation of the gothic style and therefore has shaped the design process in many ways.
The ribbed vault, as one of the three main elements of Gothic architecture, is directly related to various other elements within a structure. The earliest forms of vaulting date back to c. 6000 BC from neolithic villages where vaults were used as structural mud domes over circular dwellings. These circular domed vaults could be geometrically compared to an arch rotated on its central vertical axis unlike traditional tunnel vaults which are geometrically similar to an arch elongated along its horizontal plane.
The Mayans and Byzantines were known to have used Corbel vaults which were formed from two sets of layered corbels until they meet to form a pointed ceiling. This is the first well documented vault that could be used to support a storey above it. Far proceeding these the Romans drew on Etruscan techniques and developed the barrel vault and the, more efficient, groin vault, typically made of masonry. The thrust is concentrated along the groins and therefore only requires abutments at the 4 groin corners rather than throughout the ceiling as is required for the barrel vault. These forms became the basis from which Romanesque vaulting grew.
Myan ruins, the corbel arch found at encircleworldphotos
The Gothic style managed to lighten and heighten these heavier Romanesque vaulting systems through structural development. Yielding designs including, the rib and fan vault, both monopolising on illumination of light from all 4 sides, as well as the reduction in material required due to their greater structural efficiency.
Gothic architecture takes advantage of the most efficient geometrical forms and incorporates them into structural features of the cathedral enabling the structure to reach limits that are impossible for the Romanesque style to achieve.
When analysing the vault, we must first consider the pointed arch from which its form is based. Romanesque semicircular arches have some severe limitations. Although they are aesthetically pleasing and sturdy, the shape they adopt is inefficient. The majority of the stress lines lie horizontally, pushing outwards. In practice this means either side of the domical vault, thick walls are required to support the load pushing outwards radially from the top of the vault. This leaves very little space for windows, meaning the inside of cathedrals and churches were much darker during the daytime.
Pointed arches, influenced by Islamic architecture of Spain, direct the majority of the force downwards, with the orientation of the stress lines being closer to vertical. In a structure, this results in less force being directed to the walls and more directed to the supporting piers making the need for large heavy walls obsolete. The form closely follows that of a catenary curve, the most efficient curve shape for a load bearing structure. This can be verified by holding a piece of string at both ends and observing how it naturally falls with the equal distribution of gravitational force replicating a distributed load acting on a structure.
In order to construct these vaults a method called centring was employed where wooden frames are used as a base for the construction of masonry ribs. These ribs are the major structural element and are pasted together with mortar and left to dry until the wooden frame can be removed and the whole process is repeated. While other ribs are being constructed the infill is made.
Ribbed gothic vaults are an effective combination of these geometric features. The pointed arch distributes load efficiently meanwhile the ribs act as a skeletal structure, along which the load is concentrated. These ribs replicate predetermined load paths transferring forces to the piers which extend from the ribs down to the base of the structure. These thick piers, act similarly to the ribs and carry the majority of the load in the walls.
Nave section of Notre Dame de Paris from Wikipedia
Although the geometry of the ribbed vaults is extremely efficient, cathedrals tended to test this efficiency to the limits, soaring to extreme heights. For this reason there ended up being a large magnitude of force transferred to the base of the piers. Although the pointed arch favours the vertical plane, the stress lines are not completely vertical and so without correct support, the walls are likely to explode outwards. For this reason, buttresses were used to support areas of the walls carrying the majority of the load. Initially, buttresses were fully attached to the outer façade of the cathedral, acting as an extension of the wall with extra material to absorb the forces from the ceiling.
Progression in the Gothic Era gave rise to further optimisation in certain Gothic features. In 1179, William the Englishman introduced a flying buttress, showcased in Canterbury Cathedral, consisting of the buttress tower which connected to the outer façade only by a flyer. The first major use of fully optimised flying buttresses was in Notre-Dame de Paris added in 1220. Through the use of arched and half-arched flyers, the load transmits the thrust of the vault across the buttress tower. This skeletal extension allowed even wider spaces for wall penetrations adding a further feeling of lightness to the structure.
Due to this net structure, gothic cathedrals are able to incorporate large stained glass windows that can span between piers. These were included as another feature to bring the inhabitant of the cathedral closer to God. Many people going to church at this time were illiterate and couldn’t read the Bible themselves so stories were illustrated through the stained glass.
A prime example of this is Notre-Dame de Paris’ inclusion of a stunning, ambitious stained glass rose window of around 13m in diameter, along with a multitude of smaller versions illuminating the interior space.
Looking closer at the vaulting systems of different cathedrals we can explore the development of different vaulting systems, and how their benefits are drawbacks shaped future designs, enabling cathedrals to gradually reach higher elevations as time progressed.
Ribbed vaulting was introduced in Durham Cathedral as early as 1093, during the Norman rule of England. It is important to bear in mind, however, that many other Gothic features were later additions, hence why Saint Denis remains the pioneering cathedral of the Gothic style.
South façade Rose Window found at Pixels
The style of the vaults at Durham were driven by proportionality and the preference on linearity. This focus on aesthetics meant the stability of the vaulting was insufficient. Sensitivities within the structure meant lateral thrusts was not supported correctly. This is explored in more detail later on when exploring the transition from quadripartite to sexpartite vaulting but ultimately can result in spreading of the vaults.
Looking closer at the vaulting systems of different cathedrals we can explore the development of different vaulting systems, and how their benefits are drawbacks shaped future designs, enabling cathedrals to gradually reach higher elevations as time progressed.
Ribbed vaulting was introduced in Durham Cathedral as early as 1093, during the Norman rule of England. It is important to bear in mind, however, that many other Gothic features were later additions, hence why Saint Denis remains the pioneering cathedral of the Gothic style. The style of the vaults at Durham were driven by proportionality and the preference on linearity. This focus on aesthetics meant the stability of the vaulting was insufficient. Sensitivities within the structure meant lateral thrusts was not supported correctly. This is explored in more detail later on when exploring the transition from quadripartite to sexpartite vaulting but ultimately can result in spreading of the vaults.
The first examples of decorative English vaulting and tierceron vaulting were displayed in Lincoln cathedral. Saint Hugh’s Choir remains the oldest part of the cathedral having been constructed in 1208. This Early English Gothic exhibits a variety of unusual vaulting styles designed by master mason Geoffrey de Noiers, termed ‘crazy vaults’. Additional ribs skewed quadripartite vaults creating an inverse asymmetric pattern and preventing the bays from directly mirroring one another from either side of the choir angling light into offset directions.
The innovative vaulting scheme of Lincoln continues throughout the cathedral. Elaborate symmetrical tierceron vaulting lines the nave of the cathedral, continuous and discontinuous ridge ribs and sexpartite vaults maximising the inflow of natural light through the widened bays, and therefore windows, of the clerestory.
Notre-dame de Paris also uses sexpartite vaulting with the majority lining its nave. Quadripartite vaults, introduced in the mid 13th century became the more favourable vaulting system.
Crazy Vaults at St. Hughs Choir, from Geograph
Reasons for this change in preference have remained a mystery to historians for a long time. Many explanations have been proposed over the years, one being that quadripartite vaults are lighter than sexpartite vaults and hence more favourable for masons to construct requiring less support and making it the system more economically efficient. However, upon weighing the two different vaulting styles, spanning the same unit area, for a Princeton computer model study of ribbed vaulting, the quadripartite vault came out heavier than the sexpartite.
This unexpected result can be explained by the reduced number of ribs in a sexpartite vault per unit area. This makes sense because although the sexpartite vaults are split into 6 parts they also span a larger distance while the ribs in the quadripartite are usually constructed closer together. This result further implied there must be a larger issue than weight that the sexpartite vaulting caused making it the lesser option.
After analysing the force distribution within the vaults we can see the greater flaw of the sexpartite system that came specifically with the High Gothic. Distributed forces within the vaults act differently on the springings of the arches depending on the angle of the ribs. The angle navigates the direction of the flow of forces within each vault. Three force components need to be considered for this analysis: the vertical, horizontal and longitudinal.
In theory all of these forces are able to be supported. The vertical force is typically supported by the clerestory, piers and nave arcade, horizontal forces are counteracted by the flying buttresses transferring them to the ground and finally the longitudinal forces cancel one another out either side of the nave.
Visualisation of the force orientations within each vaulting system from JSTOR article
In practice, however, the sexpartite vaults were much more complex to erect. This is because they caused a much larger longitudinal force component, the only component of all three that had no way of being supported due to the nature of construction. All the force was distributed to the clerestory as the bays are constructed at a later period to provide stability. If the nave was particularly tall this force would also grow and apply greater pressure to the clerestory. Through experimentation of failed designs and geometrical representations masons most likely observed this change in force distribution not being conducive for the high ceilings reached during the High Gothic period. These internal forces create sensitivities that builders need to be aware of when planning the structural layout and construction process. Safety margins became tighter in mid 13th century due to the clear instability of Beauvais and Amiens.
Beauvais was the tallest Gothic cathedral ever built, reaching 47.5m before its collapse in 1284. With the majority of its official records being destroyed, the question of what exactly caused the collapse of this cathedral still remains a mystery. There seemed to have been many small errors including but not limited to insufficient foundations, incorrectly spaced piers, the incorrect design of certain parts of the superstructure, as well as the critical lack of upper buttressing.
The collapse of Beauvais cathedral rose alarm bells to future cathedral designers and in the years progressing Europe saw a decline in elevation heights and more precision during planning and construction. The allowed Amiens Cathedral, constructed in 1220, to regain its position as the tallest cathedral for a period.
The dimensions of Amiens cathedral were extraordinary to the point of near collapse, with a stone-vaulted nave reacting 42.3m. After the success of Chartres masons and designers had more confidence in the capabilities of the Gothic structure in enabling larger vaults to be erected. The interior was also monumental estimated to be 200,000 m3 in volume.
In 1498, well regarded mason, Tarisel, noticed weaknesses in the structure. Upon analysis it seemed flying buttresses for the nave and transept was not adequate and required strengthening. Furthermore, large pillars holding the transept were unstable under the strong thrust of pointed archways. An iron wall tie was used around the whole structure, sufficiently stabilising the cathedral.
The progression of the mastery of Gothic masons was very rapid considering the lack of technology at the time. In the late 14th century England had started using further decorative styles of vaulting, a major style being the ‘fan vault’ displayed in Gloucester cathedral in which ribs line the surface of an inverted cone, equally space out each connecting to lien vaults which form the web like ceiling perpendicular to the walls.
This type developed from experimentation with the vault being formed of different shapes while still maintaining the pointed arch outline. The meeting of two inverted cones managed to recreate this efficient shape. Over time the fan vault style developed showing progression through shape optimisation and the addition of more ribs. This optimisation lent itself to the return of Roman construction in pointed masonry, which was often preferred. English cathedrals in general were not as ambitious in height as French, most likely due to the angle of sunlight remaining fairly low for the majority of the day. The Gothic style, however, has always been prominent in English history with the Palace of Westminster along with St. Pancras Renaissance Hotel.
Fan Vaulting at Gloucester Cathedral, from Geograph
Vaulting of La Sagrada Familia, from SAH
The extensive use of the Gothic in England and France soon infiltrated to other European countries. Barcelona’s Sagrada Familia used an innovative style of vaulting known as the Catalan Vault involving the layering of bricks and mortar. Gaudi uses double twisted forms taking inspiration from nature, parabolic and hyperbolic shapes in order to create the vaulting columns.
Similar to traditional Gothic cathedrals there is an emphasis of verticality and light with the height of the nave reaching 45m as well as light infiltrating into the structure from above.
Reasons for this change in preference have remained a mystery to historians for a long time. Many explanations have been proposed over the years, one being that quadripartite vaults are lighter than sexpartite vaults and hence more favourable for masons to construct requiring less support and making it the system more economically efficient. However, upon weighing the two different vaulting styles, spanning the same unit area, for a Princeton computer model study of ribbed vaulting, the quadripartite vault came out heavier than the sexpartite.
This unexpected result can be explained by the reduced number of ribs in a sexpartite vault per unit area. This makes sense because although the sexpartite vaults are split into 6 parts they also span a larger distance while the ribs in the quadripartite are usually constructed closer together. This result further implied there must be a larger issue than weight that the sexpartite vaulting caused making it the lesser option.
Italy also borrowed parts of the Gothic style, demonstrating its adaptability to accommodate varying interpretations that fit better with local conditions. Italian builders were experts in the domed vault and the cultural opinion didn’t seem fond of external buttressing. For this reason Italy incorporated the domed pointed arch vault in their designs. Milan Cathedral remains the most famous piece of Italian Gothic architecture, with its nave height of 45m equal to La Sagrada Familia, and extremely close to that of Beauvais, without the use of flying buttresses.
The rapid development of the Gothic style enabled it to become one of the most influential in architectural history. Overcoming the heavy criticism from a Romanesque dominated Europe, it rose to full glory displaying the potential of the ribbed skeletal system aided by the efficiency of the geometry used.
Milan Cathedral, my own photo
The style saw great variation in its evolution, with the majority of early experimentation being completed in England and France. This paved the way for a multitude of future design and variation showcased in different European countries. The skeletal system influenced future innovations in architecture, igniting the use of ribbed systems as a structural framework. Furthermore, Gothic vaulting built greatly on our understanding of vaulting systems pathing the way for future optimisation in other styles. Culturally it signified the revolutionary attitude of society, breaking away from the constraints of the Romanesque, in order to surpass parameters unimaginable using previous construction methods.
