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The Llibre de trasas de viax y muntea by Joseph Ribes is a manuscript on masonry and stereotomy written at the beginning of the 18th century in Barcelona (Fig. 1). A most notable characteristic of this work, due precisely to the time of writing, 1708, is the extensive chapter dedicated to Gothic grid crossing vaults (Fig.2). Joseph Rives, in this treatise, studies forty grid crossing vaults and arranges them according to the number of their keystones, from the vaults with only one keystone to the ones with sixteen. Most of the vaults have a central symmetry (Fig. 3), carried out with sometimes unprecedented designs in the Spanish Gothic style. Among them is the design of a singular vault (Fig. 4), the netgewolb, a German-style net vault. This is the reason which explains the decision to build this vault of unusual geometry, both in Castile and Catalonia (Fig. 6).
The vaults which Ribes studies in the manuscript have a common characteristic: all of them are vaults of spherical intrados (fig 5). Regardless of the geometry of the plan, whether it is polygonal or circular, all the designs are carried out with round arches and a round rampant arch. Probably, Ribes draws his vaults with a spherical geometry to simplify the drawing and, at the same time, to highlight and compare the ribs of the different monteas of the treatise more easily. However, the spherical geometry of a vault wall implies that all its ribs have different curvatures and, consequently, its voussoirs must be built with the curvature of each arch, which complicates the construction of the vault considerably and gets it away from the principles of standardization of the Gothic style. This difficulty increases in the case of the vault under study due to its net design, typical of the German Gothic style. The second singular characteristic of J. Ribes's vaults is that all of them have inclined keystones, that is, they are directed radially towards the center of the vault.[....]
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