This evolution in style, from the Romanesque to the Gothic, was made possible by a dramatic technical revolution, the invention of the ribbed groined vault.
Historians agree that this revolution took place in Normandy, in the second half of the 11th century. But where? Which church or cathedral, which abbey was the first with such a vault over the nave?
The oldest surviving example can be found in the abbey of Lessay, deep in the Cotentin peninsula, far from the centers of learning of the Seine valley or from the seat of ducal power. The abbey was founded in 1056 by the Lord of La Haye du Puits, Turstin Haldup. At first, six monks came from Bec-Hellouin, where Lanfranc, an Italian monk who had become Duke William's confident, was abbot. The construction of the church did not start until 1064 and proceeded very slowly. Then in 1084, a chart, which has disappeared, was signed by the bishop of Coutances and William, now Duke of Normandy and King of England, confirming the establishment of the abbey church. How much of the structure was completed at that time, we do not know, but it may have been completed in 1094, when Turstin Haldup's son, Eudes de Chapel, died and was buried in the choir. It seems that the two earliest bays of the nave were designed to receive a wooden ceiling and that, at some point, the plans were changed to accommodate the ribbed vault. In the last 5 bays, the building technique has clearly evolved and is more functional and harmonious. Still, it is far from perfect, and one feels a real hesitation in the design and a certain clumsiness in the execution. The ribs are thick and heavy, their junction with the columns not well integrated, and the dimensions of the church are modest. Were the builders in this remote corner of Normandy just trying to copy the vault from one of William's abbeys?
William and Matilda, the daughter of the Count of Flanders, were cousins, and when they got married, they were excommunicated by the church on reasons of cosanguinity. Lanfranc was sent to Rome to negotiate with the Pope. For the redemption of their sin, the newlyweds would have to build two abbeys. William's abbey church, the Abbaye aux Hommes, was consecrated in 1077, just a few years before Lessay. This is where he wanted to be buried, and there is no doubt he would have demanded the best from his architects. But the original roof has disappeared, and the ribbed groined vault we see today above the nave dates from about 1105- 1110.
The earliest clues may come from the abbey of Jumieges. Notre-Dame de Jumieges was started in 1030. The chancel went up first, with an ambulatory around the choir, a clear break from the Romanesque tradition, where the choir generally ended in a rounded oven vault. Work on the nave started in around 1050. William was now the undisputed master of Normandy. The Norman abbeys, destroyed by the Vikings two hundred years earlier, were richly endowed by the Dukes and their vassals. Their reputation as centers of learning attracted monks from as far as northern Italy. Guillaume de Volpiano was abbot of Fecamp, and Lanfranc, a native of Pavia, moved from Avranches to Bec-Hellouin in 1041 to become abbot there in 1045. The times were ripe for William to show his power, and build a church as had never been seen before. The Lombards had used the transverse arch in some of their churches as early as the end of the 10c, and, without doubt, scholars like Guillaume de Volpiano and Lanfranc would have known about this technique. Did their disciples span the nave of the new abbey church with a new form of vaulting?
Jumieges is in ruin today, destroyed during the French Revolution by a local businessman who used it as a stone quarry. It is still a majestic structure, wide, higher than any church built at that time, the upper wall pierced with high windows. One can easily imagine an elegant ribbed vaulting spanning this wide space. But the records show that the vaulting had always been a simple wooden ceiling. Yet, in the few arcades of the aisles that remain, the groins - the lines where the arches meet - are edged with "ribs" of stone, a major advance over the Italian technique. And, in the ruins of the nave, one can see that, along every other pillar, runs a narrow column of stone. In every Gothic church, the same columns support the ribbing of the vault. Did the builders of Jumieges try it, and failed? Romanesque arches rest heavily on huge pillars, their weight directed to the ground. But the ribbed vault exerts its pressure horizontally, toward the outside of the arch, and these forces have to be absorbed by the walls. At Jumieges, the three-story elevation above the aisles, cut with wide and tall clerestory windows, formed a relatively thin wall, incapable of supporting a ribbed vault.
One then has to go back to Caen, and stop at Matilda's abbey, the Abbaye aux Dames. There, across the nave, on alternate pillars, run heavy Romanesque arches. But the space in between is filled with a groined transverse arch. Above the aisles runs a tribune, opened to the nave, with thick outside walls and strong arches buttressing the pillars of the nave. Was it an experiment, an intermediate step in trying to correct the problems encountered at Jumieges?
Back at the Abbaye aux Hommes, one can now have a closer look at the nave. Like in Jumieges, the rib supports run along alternate pillars. Like in the Abbaye aux Dames, a tribune covers the aisles, with heavy buttresses resting against the pillars, but here, the windows in between are high and wide. Williams' architects would only need to replace the Romanesque arch of Matilda's abbey with a true ribbed vault across the wide nave. All the elements of the Gothic style are in place, and it is quite easy to imagine that the original vault could have been essentially similar to the one we see today. And yet it seems that here, like in Jumieges, the nave was originally covered with a wooden ceiling. Why would William's architects design and build all the necessary infrastructure to support a rib vault but not implement it? Were they still unsure of their skills? Did they want to attempt it first in some place that was not as visible as the Duke and King's own abbey?
Was Lessay then the last laboratory test, the first attempt that actually worked. Was it here, deep down into the Normandy countryside, that the Gothic revolution started?