ABSTRACT
In an age of mass-produced steel trusses, the structural mechanics of medieval timber roofs may be easily overlooked, especially when hidden by masonry vaults. In an open-timber roof, where the structural carpentry is fully visible, the technological challenges of span and stability are augmented by a societal desire for artistically pleasing timberwork that harmonizes with the masonry structure which it surmounts. In the hammer-beam roof the hammer-beam frame is the main supporting truss for the common-rafters. Concomitant with the development of wall-plates and sole-pieces as well as the carpenter's seeming preoccupation with the lower part of the roof's structure, was the creation of a simple. By the late thirteenth century the structural concept involved at Dijon and Rolduc appears in a large cathedral roof, that above the choir of Tours. As in the Soignies roof, the tie-beam frames at Angers are reduced in number and actually rest on the masonry of the vaults.
