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Saint-Pierre de Beauvais | The Collapse of the Choir in 1284 and the Subsequent Rebuilding
Professor Stephen Murray

The Collapse of the Choir in 1284 and the Subsequent Rebuilding
"On Friday November 29 at eight o'clock in the evening the great vaults of the choir fell, several exterior pillars were broken, the great windows were smashed; the holy châsses of Saint Just, Saint Germer, and Saint Evrost were spared and the divine service ceased for forty years."1 Historians have suggested a variety of different reasons for the collapse—from moralizing (a Tower of Babel scenario) to a simplified response to the choir's enormous height. The only real evidence that we have to help us comes from the analysis of the edifice itself.

An attempt to ascertain the extent of the damage caused by the collapse encounters a gap between the understanding of the event based upon the analysis of the masonry and the results of the recent dendrochronological analysis of the timbers of the roof. It is clear from the masonry that everything from the sill of the triforium to the clerestory in the choir straight bays has been rebuilt. The hemicycle, more rigid on account of its curved profile, remained intact.



France, Beauvais, Cathedral, South side of choir
 

France, Beauvais, Cathedral, North side of the choir
 

France, Beauvais, Cathedral, East end of the choir

In the straight bays additional supports have been interposed between the piers of the main arcade, transforming three bays into six and quadripartite vaults to sexpartite. Old material was re-used in the reconstruction of the vaults and in the tracery of the clerestory windows. Each original clerestory window had six cusped lancets surmounted by a great oculus. The clerestory wall in the straight bays has been entirely rebuilt and is much thicker than the hemicycle clerestory. The intermediary pier dividing the two choir aisles on the north side has been replaced in the fourteenth century. The matching pier on the south side may also have been replaced: the present unit was rebuilt by Martin Chambiges in the sixteenth century. On the exterior of the edifice the chapel window in the easternmost bay on the south side of the choir has been consolidated and rebuilt, and the main and intermediary culées in the middle bay of the choir on the north and south sides have been replaced from the level of the aisle roofs. The rebuilding of the main pier buttresses in the choir clerestory in the hemicycle probably belongs to same period.

From the above it might be concluded that the disaster of 1284 was a major event, involving the collapse of all three straight bays of the upper choir. However, recent dendrochronological analysis of the main roof of the choir has indicated that although damaged, the main roof of the choir survived the collapse. The massive extent of the post-collapse rebuild was not so much a direct result of the need to replace portions of the edifice that had collapsed but reflects an atmosphere of fear and conservatism in the aftermath of the disaster. The collapse probably involved principally the failure of the transverse arch in the middle bay of the high choir and the fall of the contiguous cells of vaulting. The high vaults and windows that survived were then taken down and rebuilt using bits of the old masonry.

Recent research has emphasized the role of wind buffeting and oscillation that would dislocate the cul┌es and flyers. Wind tunnel tests have confirmed that such forces can have a local effect upon certain units that were particularly vulnerable on account of the orientation and configuration of the edifice.



France, Beauvais, Cathedral, Time-elapsed photo showing oscillation effects of wind forces
 

France, Beauvais, Cathedral, Simplified plan showing misalignment in the hemicycle
 

France, Beauvais, Cathedral, Section

Certain inherent design characteristics rendered the middle bay of the choir particularly vulnerable. This was the broadest bay with a main vault canopy more than sixteen by nine meters—an area much greater than in any contemporary cathedral. The misaligment of the hemicycle means the northern side of this very wide bay is significantly wider than the south.

The outward thrust from the main vault over this over-extended bay was met by rather horizontal flyers supported by main culées which, because of the pyramidal section of the choir with its low outer aisles, were extremely tall, leaving a large part of their height exposed to the wind.

In addition, the intermediary aisle piers were inherently unstable and tend to rotate towards the interior, propelled by the vaults and arches of the low outer aisle. These very slender intermediary aisle piers formed an unstable base for the intermediary uprights placed slightly overhanging (porte à faux) the inner aisle.

The combination of an inherently unstable infrastructure with a very large vault in the middle bay of an unusually tall choir and the play of high-velocity winds and local turbulence would explain how the edifice could have stayed aloft for twelve years before a collapse that might have occurred in or after a severe storm.

Reconstruction work completed until the 1340s, was radical. Three bays were made into six with the addition of main arcade piers and sexpartite vaults. The upper choir was entirely rebuilt in the straight bays with elements that were partially re-used. The culées in the middle bay of the choir were rebuilt, the main units with fins that would correct their tendency to oscillate in high winds. It took longer to repair the choir than to build it: a situation to be understood in light of the uncertainties about the causes of the catastrophe and funding difficulties caused by further local disturbances and the onset of the Hundred Years War.

   
1.   Collection Bucquet-aux Cousteaux, XXIII, p. 1, Municipal Library, Beauvais

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