Brick vaults without centering in the church of Calatrava la Nueva: geometry and construction

Résumé

Brick vaults can be laid out in three different ways: with brick bed planes passing through the axis of the vault, with the beds parallel to the axis, or with beds approximately orthogonal to the axis. The third kind, known as vaults by slices, avoids the need of falsework and fast-setting mortars, in particular when courses are laid in moderately sloping planes. The church of the castle-convent of Calatrava la Nueva, in Central Spain, built in 1220–1240, holds a remarkable ensemble of brick vaults by slices, including severies in rectangular rib vaults, sail vaults, quarter-of-sphere vaults and a semi-polygonal vault. The ensemble has been surveyed using 3D laser scanning and Structure from Motion photogrammetry. While the general layout and the execution of the stone arches and ribs are acceptably precise, the geometry of the severies and vaults by slices does not follow a precise geometrical model, suggesting that neither formwork nor specific formal control instruments were used. This may be justified by the need to build the castle and the church quicky, to secure an important stronghold in the Córdoba-Toledo route in the aftermath of the decisive victory of the armies of Castile, Aragon and Navarre in the battle of Las Navas de Tolosa in 1212.