By Stan Parry 

The Formation of The Gothic Style

Author's note: What follows is a brief excerpt from the book's introduction explaining how the pointed arch, ribbed vault and the flying buttress came into being and affected the development of Gothic architecture. A diagram illustrates how Gothic builders dealt with the enormous structural stress these monumental buildings created.

The key elements of Gothic architecture are generally considered to be the pointed arch, the ribbed vault, and the flying buttress. It must be remembered that the ribbed vault and pointed arch were present before Gothic, and the flying buttress was really a response to the demands created by those two elements that did not come into play until Gothic was well under way.

The Ribbed Vault-A Stroke of Genius
To understand Gothic architecture it is essential to take some time to consider the ribbed vault, which soon came to dominate medieval construction for a variety of reasons. The ribbed vault was as critical to the development of Gothic architecture as was the steel girder in the nineteenth century or reinforced concrete in the twentieth century. The ribbed vault gave the builders a flexibility of design and construction that was simply not possible with the barrel or groin vault. It was easier to construct than the barrel or groin vault, and it was stronger and more flexible.(See book for Fig. 6)
The ribbed vault is made by combining three separate but connected arches. These are the transverse arches that span the ends of the vault, the lateral or longitudinal arches that span the length or sides of the vault, and the two diagonal arches that reach from corner to corner...

The diagonal rib or arch was a stroke of genius. Instead of one large curved surface to cover with a webbing of concrete, the vault was divided into smaller sections or cells that could be filled with concrete. The builders quickly realized that by using cut stone instead of concrete, they could fill in each section without huge forms underneath to support the webbing. After the arches were in place, it was simpler to place the stones between the various arches or ribs. This is similar to constructing a curved brick wall within the frame of the intersecting arches.

The Pointed Arch-Flexibility and Strength
The second great advantage of the ribbed or arched vault was the flexibility it gave to the builder. This came about not by using a diagonal arch but by breaking the round arches. A broken arch becomes a pointed arch. The breaking of the round arch allowed the builder to vary the height of each of the three arches, the transverse, the longitudinal, and the diagonal...

Pointed arches, whether transverse, diagonal, or longitudinal, can be of different widths to span different distances and still have the same height because the pointed arch can be made narrower or wider to adjust to the width at the base. A sharper point for a narrow base on the ends of the vault can coexist with flatter pointed arches that support the sides. The diagonal arch is the flattest and longest of the three.
This gave the builders tremendous flexibility. They could create vaults over any sized rectangle or even over triangles, trapezoids, pentagons, or whatever the builder needed. This flexibility was crucial in the choirs and ambulatories of the churches where the aisles needed to curve around the eastern end. The development of the triangular vault allowed the designer to build a fan of ribs to cover the center of the choir vault. The ambulatory vaults of Bourges and of Notre-Dame in Paris are good examples of this flexibility.

The Flying Buttress
Not all of the weight of the vaults, however, can be channeled downward. There is always lateral thrust as weight tries to spread outward. With the barrel vault the lateral thrust is considerable and has to be met with thick walls or with side aisles that serve as buttresses to the main vaults. In effect, the vaults of the side aisles served as raised buttresses. It was probably to be expected that the first vaults to be ribbed at Durham Cathedral in England and Saint-Étienne at Beauvais would be in the aisles (See book for Fig. 11) The ribs of the aisle vaults could reach over the aisles from the massive exterior walls, which allowed the builder to open the aisle arcade to the nave. Hidden under the aisle roofs, the aisle vault arches were really the first flying buttresses. In reality, the flying buttress is the arch of an aisle vault raised above the aisle roof to the position where it absorbs the most thrust from the main vaults.
The invention of the flying buttress was a later development, although there is now some academic debate as to the actual dates.

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