Plan B and the Geometry of Façade Design at Strasbourg Cathedral, 1250-1350

Abstract

A remarkable series of medieval drawings in Strasbourg documents the emergence of the local cathedral workshop as a major center of Gothic design around 1300. The so-called Plans A and B, in particular, figure prominently in the literature on Gothic architecture, but the formalistic methods usually brought to bear on the drawings leave many questions unresolved. This article uses geometrical analysis to show how the proportions of both drawings resulted from the compass-based Gothic design process. This discussion reveals a striking difference between the essentially planar Plan A and the more three-dimensionally conceived Plan B, in which the octagonal plan of the intended spire played a crucial generating role. Geometrical analysis of the complete façade block, meanwhile, shows that Plans A and B continued to influence the façade builders in the fourteenth century, despite the introduction of a new ground plan shortly before the beginning of construction in 1277.