The Planning and Building Instruments of Architects in the Late Middle Ages
Second International Congress on Construction History (2006)
Introduction: From the instruments used by architects in the Middle Ages to the necessary knowledge for building stability: Vitruvius’ firmitas: this is the proposed deductive method. The following deductions represent a sort of circumstantial investigation where practically no certain evidence exists, we shall nonetheless endeavour to demonstrate that they were all possible with the knowledge of the time: this is not to say, of course, that such were their methods, however something quite similar was certainly employed. The architects of the time have hardly left any trace of their planning and building methods, almost as if to preserve the secrets of their workshops, limiting to the bare minimum their revelations: only what was absolutely essential to actually carry out the building came out of their chamber des traits (drawing studio), nothing whatsoever concerning the design procedures. There exist few exceptions with some sort of evidence and among them there is the drawing of the rose window of the cathedral of Chartres, transferred by Villard de Honnecourt, not as it was successively built, but during a planning phase, which leads us to presume that he was in some way linked to the architects who were actually working on it.
The development of building techniques in the architecture of the late Middle Ages, which is considerably different from that of the previous centuries, seems to be the result of a natural evolution of building techniques rather than a continuous search for improvements to apply to better and more logical workmanship.
Even if in a cryptic manner, this is visible in Villar de Honnecourt’s Livre de Portraiture which could be considered the builder’s manual of the time, an avant-garde handbook for the building and perhaps even the work optimization solutions it contains.
Among the evidence present in the architecture of the time, the drawing (folio 21 recto), known as the rule of the three arches, is particularly significant. “Par chu fait om trois manieres d’ars a compas ovrir one fois”, by opening a pair of compasses only once three types of arches can be inscribed: a round arch, a quarter lancet arch and a pointed arch that have the same radius in common and all that derives from a constant radius; centring curvature, ashlaring, but above all the organisation of the building yard and the different ways of assembling equal elements.