Design and medieval construction: The case of Tortosa cathedral (1345-1441)

Gothic design and construction was generally dependent on the knowledge of the magister operis but, in the case of cathedrals, it was finally determined by the influence of the Chapter. The knowledge of these two protagonists and the transfer of their learning suggest that the construction of certain buildings were, effectively, based on experimental designs. The remarkable Archivo Capitular (Chapter Archive) of the Cathedral of Tortosa preserves not only the masonry books but also the designs of Antoni Guarc (c. 1345-80) and the scientific texts of the canons. These sources have facilitated an epistemological study of the knowledge that enabled the building's designer to meet the challenge set by the Chapter to build the ideal of the City of God. The construction of the apse of Tortosa cathedral (1345-1441) was an experiment aimed at the total elimination of the wall from the radial chapels, using a cross section with a very low span-to-rise ratio (9/5). When its stability was confirmed, the ratio was increased in the construction of the ambulatory (9/6). The builder then provided a design solution on site of the enigmatic heptagon, based on a proportional theory (9/8). The methodology used by the designer was inspired by a Neoplatonic proportional theory, founded on the scientific texts of the library of the canons.