The work proceeded rapidly, commencing at the east end. By the time of Bishop Carileph's death, which occurred in 1096, the walls of the choir, the eastern walls of the transepts, the tower arches, and a portion of the first bay of the nave, were completed. It is also very probable that the lower portion of the walls of the whole church are of Carileph's time.
After the death of Bishop Carileph the see of Durham remained vacant for three years. The monks, however, were not idle during this period, and they continued the work vigorously, completing the west walls of the transepts and the vaulting of the north transept. In 1099 Ralph Flambard was appointed bishop, and he held the office until 1128. He carried on the building as the funds at his disposal would allow, sometimes rapidly and at others more slowly. Before his death it would appear that he completed the nave as high as the wall plates and altogether finished and roofed the aisles. The western towers as far as the height of the roof of the nave are also the work of Flambard. In 1104 the work was so far advanced as to permit the removal of the body of S. Cuthbert, from the temporary shrine which Bishop Carileph had erected over it, into the new church. This ceremony was performed on August 29th, 1104, and the coffin was placed in a shrine behind the high altar.
On Flambard's death in 1128 the see was again left vacant for five years, but we are told that the monks continued the work and completed the nave. The portion built by them at this time must of necessity have been the vaulting and roof, the architectural features of which are quite in accordance with the date, being late Norman.
Flambard's successor was Galfrid Rufus, who was Bishop from 1133 to 1140.
During his episcopate the chapter-house, which had been commenced by the monks, was completed. Rufus also replaced the then existing north and south doorways of the nave, by those standing to-day.
The next bishop, William de St Barbara (1143 to 1152), does not appear to have added anything to the cathedral. During his time of office the see was usurped by William Cummin, and building operations were no doubt neglected through the troubles arising from the usurpation. His successor, Hugh Pudsey (1153 to 1195) was, however, a great builder; appointed to the see at a comparatively early age, and, living as he did, at a time when very great changes were taking place in architectural style, he was able to carry out a great deal of beautiful work.
He began to build a Lady Chapel at the east end of the choir, but although he had made careful preparations, and engaged skilled architects and workmen, great cracks appeared in the walls before the work had proceeded far, and the building was stopped. Bishop Pudsey, taking this as a divine revelation that the work was not pleasing to God, and the patron S. Cuthbert, abandoned it and commenced another chapel at the west end of the church, using in its erection the Purbeck marble bases and columns which he had had prepared for his eastern chapel. This second attempt was successful and remains to us in that beautiful and unique specimen of Transitional work, the Galilee Chapel. Its date may be taken, says Canon Greenwell, "as about the year 1175." Besides this work Pudsey built the hall and solar now called (at the top) the "Norman Gallery" of Durham Castle.
Little or nothing further seems to have been done until the translation of Bishop Poore from the see of Sarum to Durham in 1229. The name of Bishop Poore is inseparably connected with the building of the present Salisbury Cathedral, and after his removal to Durham he conceived the idea of, and made preparations for, commencing the eastern transept of the Cathedral, which is a special feature of Durham, now known as the Chapel of the Nine Altars. He was not, however, destined to live to see his idea carried out.
The eastern termination of Carileph's choir had been apsidal; it was found to be in a very unsafe condition, cracks and fissures appearing in the walls. Various bishops and priors sent aid towards "the new work," but actual building did not commence until after the death of Bishop Poore in 1237. The erection was commenced by Prior Melsanby and, of course, necessitated the taking down of Carileph's apses. The revaulting of the choir was undertaken at this time, doubtless, for artistic reasons, to bring the new work into harmony with the old. The Chapel of the Nine Altars is a rare and valuable specimen of Early English Gothic architecture of remarkable and graceful design. Below each of its nine lancet windows was originally an altar, dedicated to different saints. Its great height was obtained by lowering the floor, so that the unity of the whole exterior should not be destroyed. Prior Melsanby is also said to have put a new roof on the church.
Prior Hugh de Derlington, who was at the head of affairs from 1258 to 1272, and later from 1285 to 1289, added a belfry to the central tower.