In some Gothic monuments, the wall inclines outwards at the height of the triforium (Chalon-sur-Saône Cathedral, Saint-Martin Church of Clamecy). The triforium is a horizontal passage running through the main piers which are critical to the stability of a monument. I examined the masonry of the triforium in several monuments and the plans at the height of the triforium (available at the MAP (Médiathèque de l’architecture et du patrimoine) of Paris or the online database “Mémoire”). The study has shown that several security measures could be taken to diminish the risk of weakening the piers.
This paper investigates the three solutions at the intersection of passages and piers (Fig. 1): 1. Passages running through the piers (reinforcement by internal buttresses); 2. Passages turning around the piers; 3. Blocking-up of the passage.
1. Passages running through the piers (reinforcement by internal buttresses)
The passage continues through the piers. The section of the pier decreases at the height of the triforium. This solution was already common in the Romanesque clerestory passage. At the intersection of the passage and the pier, the construction is reinforced employing additional masonry (internal buttress) which reduces the height of the passage (Fig. 3). At the Amiens Cathedral (Fig. 4, 5), the width of the passage is also reduced, but in most cases, the passage runs without narrowed (Cathedrals of Soissons, Meaux, Lyon (Fig. 6-9), etc.). From around 1200, the masonry of the pier comes to be made by large ashlar blocks instead of small blocks and rubble fills (Fig. 10-15). This seems to contribute to ensuring the stability of the pier.
2. Passages turning around the piers
The passage turns around the piers instead of running through them. The rear wall of the triforium bends toward the attic. This solution can be seen in tall cathedrals in southern France (Narbonne, Limoges, Rodez (Fig. 16, 17), etc.) and monuments without aisle attic (lower triforium of Beauvais Cathedral, Mont-Saint-Michel (Fig. 21, 23), etc.). At the Auxerre Cathedral, the choir triforium (c. 1215-) was blocked up after the risk of collapse became urgent, which later led the nave triforium (14th century) turn around the pier from the beginning (Fig. 20).
3. Blocking-up of the passage
In order not to reduce the section of the piers, some passages were simply blocked up at the intersection, from the beginning or afterward (Fig. 24, 25). To block up or not the passage depends on the judge of the master/architect of the building. In some monuments, after the passages in the preceding parts were plugged because of safety reasons, they were blocked from the beginning in the following parts (Saint-Quentin (Fig. 24, 27), Troyes Cathedral). At the Noyon Cathedral, the architect decided to condemn the passage to ensure the stability of the thinned piers (Fig. 26).
The examples of Auxerre, Saint-Quentin, Troyes, Noyon shows that the triforium passage was thought to endanger the stability of the pier. Both the triforium and the pier-centered construction were widely pursued in Gothic architecture; to keep both of them would have been an important problem for architects.
