A 7-bay ailsed nave is terminated to the west by a three-bay narthex and to the east by the crossing from which two-bay transept arms are generated. The three bays of the 5-aisled chevet lead to a five-segment hemicycle, an ambulatory and three radiating chapels -- the chevet plan recalls Rouen and Meaux Cathedrals as well as pre-Gothic Chartres. This is an ambitious architectural program, clearly inspired by cathedral prototypes.
The chevet has a three-story elevation: an arcade supported upon slender cylindrical columns, a skinny triforium and a very tall clerestory. In the hemicycle the clerestory windows have no tracery -- bar tracery appears in the chevet straight bays.
The chevet-type elevation continues into the east side of the transept arms and west side of the north transept, but is transformed in the nave where the arcade is much taller and the triforium is omitted making a steep two-story elevation. The nave supports are a form of pilier cantonné with a bundle of shafts on the front surface.
Work on the chevet began c. 1220-25 and progressed quickly into the transept and nave (c. 1235). The construction of the western bays of the nave and narthex , however, was delayed until the 14th century
A single thirteenth-century portal is located on the north arm of the transept. The scenes that take up the majority of the tympanum and lintels comes from the legend of the apostle Thomas in India. In the archivolt above, the labors of the months appear in the relatively wide voussoirs.
At the apex of the tympanum, we see Christ's head and torso above a cloud-covered border. He holds an orb in his left hand, and offers a gesture of prayer with his right hand. He is flanked on either side by crouching angels waving censers. In the register below, proceeding from left to right, we can decipher the incredulity of Thomas; Christ urging Thomas to accept the invitation from the king's steward to go to India and serve as the architect to a king there; finally, at the right within this register, we see catch a glimpse of Thomas' journey to India by boat. In the lowest register, the narrative progresses from right to left, beginning with a wedding banquet, at right. The central scene continues the narrative, where we find a representation of the king, his steward, and Thomas discussing plans for the king's palace. Another detail from the hagiography of Thomas follows, with the saint doling out food or alms to the poor. Finally, at the far left, Thomas depicted conveying a blessing to a woman, an act overseen by a man in a crenellated structure, who rests his hand in his hand.
Although sculpted depictions of Saint Thomas are uncommon in the thirteenth century, Kenaan-Kedar rightly emphasizes the likelihood that Thomas's almsgiving was emphasized as an "exemplum to demonstrate the value of Works of Mercy," which became increasingly important after the Fourth Lateran Council of 1215.
According to Williamson, the portal of the north arm of the transept dates to around 1250.
The Semur master as one who travelled and picked up motifs from elsewhere while at the same time establishing "Burgundian style." Importance of Auxerre as germinating field.
Branner claimed that Semur nave 1230s was, with Nevers, amongst first Burgundian monuments to organize bays as total spatial units -- reception of Ile-de-France rayonnant
Henriot, M., "Les foires de Semur-en-Auxois," Annales de Bourgogne, 6, 1934 371-380
Truchis, P. de, "Semur-en-Auxois," Cong arch (Avallon) 74, 1907, 64-79