I’m going to try here to accomplish in short form something that is almost impossible – an overview of medieval vaulting. In theory, the task should be simple, but the subject is extremely complex. It starts with a sequence of arches that forms a continuous tunnel and thereby covers an enclosed space. The first example is the simple barrel vault found in the Cistercian monastery of Senanque.
Because of the difficulty of building an entire vault in one pass, the vaults were segmented by bands and built sequentially. This saved significantly in materials (framing for an entire vault instead of framing for sections of vaults that could be reused) and allowed the load to be distributed somewhat by the bands down the piers and into the ground. The result was something like this in the image of the vaults of Saint Trophime in Arles.
The next step was the use of the groin vault, which is officially described as “the perpendicular intersection between two barrel vaults”. In this version of the vault, the seams between the intersecting vaults take some of the thrust and guide it down through the piers to the ground. This is a significant improvement over the barrel vault in that it eliminates the continuous lateral thrust on the side walls and allows for the insertion of windows in the wall groins. This can be seen in the rare groin vaulting over the nave at Vézelay.
It is possible to construct a groin vault only over a squared volume. In this case, as in most, the each groin vault must span two nave bays instead of one. This was a large area to cover and often resulted in weaknesses that caused the vault to collapse. To increase the strength of the groin vault, builders began adding another span between the two central pillars, resulting in a vault split into six parts, not four. This was the sexpartite vault. These two shots from the great cathedral of Laon show how the sexpartite vault looks.
At this point, the medieval builders made the great discovery that the strength of the groin vault was the groin itself, so they started constructing the groins and then filling them in with the stone voussoirs. This broke the “square” rule and allowed oblong volumes to be vaulted. Because of construction and engineering exigencies, the art developed over time until it became the wonderful groined gothic vault, the quadripartite, so familiar in its simple and its flamboyant multiple ribbed versions.
This is a story that becomes increasingly complex and difficult to sequence. I used to think that the Romanesque vaults were the records of the failure of medieval engineers, and that when they succeeded in overcoming the limitations of their early efforts, they evolved the quadripartite. But there is more to this story than mere engineering and construction. It is also the story of artistic vision and rhythm, of creating an effect that contributed to the overall visual design of the house of God. Its message was as important as its structure.