| During the Decorated period in England carpenters were hired to design and construct roofs for a challenging new building type---large, centrally-planned, usually polygonal, chapter houses and crossing towers. In their designs, carpenters strove to provide rich patterning of curved roofs and ceilings. At the same time, carpenters balanced shortages of the extremely long, straight timbers needed for large-scale timber framing and a corresponding abundance of medieval labor. Between 1259 and 1340 carpenters developed several new solutions to this particular design problem and simultaneously changed the craft of carpentry as a whole.; A close examination of the six remaining timber frames of this type clearly shows that by 1300 carpenters: (1) employed a much wider variety of rectangular cross-sections, (2) incorporated more curved members in structurally important locations, (3) phased out an older method of framing, referred to in this dissertation as "overlap framing" in favor of a new style of framing called "independent assembly framing," and (4) revealed an appreciation of the forces inherent in their structures through increased use of labor-intensive housed joints.; Structurally, simplification appears to have been the order of the day, as carpenters eliminated long passing braces, shortened timbers, cut tie beams, and abandoned redundancy. Instead of spreading out wind and gravity loads through an array of overlapping timbers, carpenters chose to concentrate loads on fewer timbers connected by better joints. These tactics had many weaknesses, including larger stresses on joints and members, and also heavier loads transmitted downward into the masonry substructures.; However, between 1250 and 1350 carpenters also increased the geometrical and spatial complexity of their designs, shifting from thinking primarily in two dimensions to planning in three. Earlier frames were clearly conceived as flat, linear frames rotated around a central axis. Later frames were designed with multiple axes and concentric rings of support. William Hurley's design for the lantern over the octagon at Ely, for example, is based on at least three platforms, four vertical rotated axes, two concentric rings (rotated 22.5° from each other), and the splayed main braces that carry the bulk of the lantern's weight. |
