Before the age of structural steel, the design and appearance of buildings were severely limited due to the physical properties of the materials used. Timber buildings were, at the most, two stories tall. Adding height to a building placed great stress and pressure on the lower supporting walls. The physics of this necessitated that most structures be limited to two or three stories. Simple buildings were timber-framed, or even made entirely of wood, like the log cabins of early America or of Sweden, where the log cabin originated. But the Middle Ages were a time in which the community wanted to express their faith through glorious church design. This was the era of the building of great cathedrals. The challenge for builders was how to build ever higher without causing the collapse of the main walls. While adding thickness (depth) to the wall at the lower portions and tapering the thickness gradually as the wall was built upward was a partial solution, the problem was that walls for some of the largest cathedrals would have to be eight or even twelve feet thick at the base. It was an impractical solution. (Even the Egyptian pyramid builders understood this, which is why they hit on the design of the pyramid itself as a way to deal with the physics of stress pressure.)
One of the most ingenious solutions created by the architects of this Gothic building period was the flying buttress. Most of the famed cathedrals of Europe used this technique. What the flying buttress is, in essence, is stone support from outside the cathedral wall. Many of these structures ringed the church wall, acting as an external support. Inside the cathedral, another solution was the ribbed vault, a design feature that deflected weights and pressures from the roof down to the walls and the flying buttresses. When we look for parallels between nature and human design, we see that many insects have an exoskeleton, as opposed to the internal skeleton of humans. The cathedrals with flying buttresses were much like the exoskeleton of the insect, where the supporting systems were visible. Even on the inside of many of these buildings, other clever devices were employed to deal with the restrictions of the building materials of the time, such as vaulted ceilings which directed pressure from above down to vertical internal supporting columns. The masons of this period often learned from using trial-and-error methods to discover what worked and what didn’t work in building techniques. The majesty of the great cathedrals of Europe, such as the examples at Notre Dame in Paris, the cathedrals of Mainz (Germany), Cologne (Germany), Strasbourg (France), and many other beautiful examples of architecture of this era often took one hundred years to construct because only animal and human power was available at that time.