Some notes on gothic building processes: The expertises of Segovia Cathedral

The construction of gothic cathedrals have aroused interest in architects, engineers and historians for centuries. There is, for example, an abundant literature on gothic vault construction, and some aspects (i.e. the structural behaviour of the vault, the function of the ribs) are still alive. The finished cathedral must be in some safe state of equilibrium to survive for centuries. This is an obvious statement. There is another aspect which has been rarely considered: the cathedral must have been also in equilibrium during the building. In any of the intermediates phases, the sequence of the operations, the dispositions of scaffoldings, materials, etc., must have assured a safe state of equilibrium. This consideration implies some order in the processes. Some situations are paradigmatic; this is the case of the process of construction, centering and decentering of the flying buttresses, the main walls and the vaults of the lateral naves. The flying buttresses must be built before the vaults of the central nave, but when should they be decintered? The lateral naves must be built before the main nave. But, when can their centerings be safely removed? There are many other questions of this kind. What was the process of building a cross vault? What kind of scaffold was used? Was there a precise order on construction? What was the role of the heavy bosses? etc. The only author who has tried to answer these kind of questions is Fitchen in his book The construction of Gothic Cathedrals: A Study of Medieval Vault Erection (1961). In his discussion of these matters, Fitchen uses a Abuilding common-sense@ approach, trying to deduce the possible gothic processes from the nature of the problems involved (which he studied thorouhgly, as can be deduce for the excellent bibliography ). He assumed explicitly that between the scarce gothic original sources no information about building processes could be find. In fact, this is not the case. Since the 1960’s, the work of Shelby, Müller, Coenen, etc., have unearthed a remarkable amount of gothic technical literature on building. The case of the late-gothic architectural treatises of Lorenz Lechler and Rodrigo Gil de Hontañón is remarkable. More concrete information can be find in expertises. During the construction of a cathedral, sometimes, the Chapter considered necessary to call a foreign expert to assess the state of the work or to discuss erection problems. This was the case in Segovia=s cathedrals, where several expertises from the beginning of the XVIth century have been preserved. One of the authors (Ruiz Hernando 2003) have published recently a diplomatic transcription of these expertises. The texts are extremely difficult to interpret. They refer to a concrete phase of the construction of the cathedral, which must be identified. The vocabulary is obscure, both because of the use of old castilian words as for the complexity of the technical matters involved. What is most interesting is that some of the expertises make direct reference to the kind of questions before explained: the order and sequence of construction of the flying buttresses, the lateral vaults and the walls of the main nave. In the paper an exhaustive analysis will be made of the contents of the expertises trying to throw some light to the gothic building processes