Beginning with the ‘Carolingian Renaissance’, around 1000CE, carpentry in the Middle Ages saw a technological revolution in building, involving bigger and better apparatus, greater precision, geometric accuracy in architecture, and the perfection of woodworking tools. We know this from illustrations on parchment and tapestries from that time.
Many homes for the common folk were built according to well known standard dimensions and ‘rules of thumb’. Measuring cords, foot rules, storey poles, and framing squares were re-used at multiple building sites. Designs were often laid out full-scale on the ground using lines or marks on the ground. For larger and more complex construction, parchment made of dried sheep or calfskin provided a surface for ink and brush drawings. Sometimes, finely split birch or beech boards were used for drawing plans on. Another essential planning element was the construction of templates for the centering of windows, doors, arches, and vaults. This formwork was eventually removed and reused. A house frame was made up of modular components, so that standard-sized posts, beams, and braces could be easily copied from a prototype.
The foundation and the framing were made level using the right-angled plumb-bob or by water levels, both of which were used by the ancients. The spirit level did not develop until after the Middle Ages. Larger squares, if both arms were of equal length, could double as layout tools as well as levels when a cross-piece was added, and a plumb-bob was hung from the apex. Squares were graduated at inch intervals and used to layout joinery as well as a reference for the roof slope that was expressed as a ratio of rise over run, rather than as an angle. Other measuring and layout tools included rod, pole, and dividers, most of that were made of wood and sometimes were collapsible.
Before 1700, use of the framing square for joinery was limited and timber joints were laid out using dividers and a plumb-bob in a method known as ‘scribing’. This technique was essential in the days before timber was milled square and, as good timber became scarce, could cope with increasingly irregular pieces. The compass dividers were made up of two legs attached by a movable joint, not to be confused with a compass rose, an arc or circle with graduated angles or directions. In Middle English, the word ‘compass’ referred to any crafty device used to aid in geometry.
Many of the mysteries of carpentry are part of an unwritten tradition. Skills in geometry do not require literacy or even numeracy. In the Middle Ages, such knowledge, like all early science, had connotations of magic. Geometry was used by builders not only for design and layout but also for applying proper proportions in architecture. These standards and rules were often kept secret, and governments acted on behalf of the craft guilds to ensure monopolies on knowledge as well as on markets. In 1459, The German Congress of Regensburg declared that “no one should teach anyone not of the craft how to set up an elevation from a plan”. Legend has it that, in 1099, Conrad, the Bishop of Utrecht, was stabbed to death because he had learned a craft secret from a master builder’s son.
Mysteries of the Carpenter 