Metal has long been used in architecture, but only relatively recently has its application become conspicuous. Before the second Industrial Revolution made structural frames of iron and steel possible, metal played a hidden role in buildings. Small iron crimps, anchors, and tie rods held the massive stones of Greek and Roman monuments together. Strong and resilient yet difficult to produce at a large scale, metal has maintained a concealed structural identity throughout architectural history.
Recent findings suggest that the Gothic period represents a pivotal moment in the use of metal. Gothic architecture is typically associated with achievements in the use of stone and glass—exemplified by the soaring vaults and delicate apertures of medieval churches. Although metal reinforcements exist in these structures, common wisdom has held that such elements were added in later centuries in order to protect the buildings from settling and physical degradation.
However, a team of researchers from the Laboratoire Archéomatériaux et Prévision de l’Altération (LAPA), in Paris, has recently determined that such reinforcements were used in the original construction of these churches. Applying radiocarbon dating to the 11th-century Bourges Cathedral and the 13th-century Cathedral of Saint Peter of Beauvais, in central and northern France, respectively, the scientists determined that iron elements were employed at the time of construction.
The LAPA researchers’ method was quite clever. Realizing that charcoal was used in the Middle Ages for iron smelting, the scientists looked for, and found, trace quantities of Carbon-14 in iron carbide flakes contained within the metal. By carbon-dating these flakes, the scientists were able to determine the age of the trees used to produce the charcoal. They then aligned this age with historical chronicles of each of the cathedral's construction and found a match.
The discovery puts to rest long debates about when and how metal was applied to Gothic architecture, revealing that iron was considered by master builders during the design process as well as added during construction when additional reinforcement was deemed necessary. Thus, although Gothic architecture is most commonly associated with accomplishments in stone, its builders were clearly utilizing a hybrid material approach—one that relied on iron to make these seemingly impossible structures realizable.
Blaine Brownell, AIA, is a regularly featured columnist whose stories appear on this website each week. His views and conclusions are not necessarily those of ARCHITECT magazine nor of the American Institute of Architects.