Fun Fact of the (Bi)Week: On Building a Cathedral
People really like to build things. Always have, always will. Let’s look at one of the ways in which people expressed their reverence for a higher power and satisfied their insatiable desire to build something cool: the cathedral. The information which follows was typical for construction of cathedrals in medieval Europe, circa 1200 AD, at least according to my sources; however, it may not have been true in every case.
Work would begin with the clearance of the selected site. This meant clearing away whole city blocks, or deconstructing a previous cathedral, which was usually no small task. Once the trenches were dug, stones began to be laid on carefully maintained layers of gravel and sand. The foundations of cathedrals stretched deep into the earth, taking up an amount of building material almost equal to the structure above ground. Though invisible, these stones had to be placed with the same care and levelness as the rest of the structure, lest the stones above them be off-kilter.
The stones themselves were typically sliced out of the ground in a quarry nearby, carved to shape by a stonemason, and then carted along to the construction site in a steady stream of horse-drawn wagons. Each carved block would be marked to instruct the builders where to place the block and to tell the bookkeepers who to pay for the carving. Stonemasons would be paid per block, as long as their work was up to scratch.
Funding such an enormous project was perhaps the greatest hurdle that had to be overcome. Of course, the vast majority of money came from the local church chapter’s money, but individual donations from priests, clerics, and ordinary members of the church made a good portion of the budget. There were also significant contributions from private patrons, as well as high ranking members of the church. Particularly, there was a practice of patrons paying for specific sculptures of angels or saints, and if the mason just happened to make this extremely visible symbol of purity and divinity look like the person who paid for it, well then, that would just be a very convenient coincidence.
Cost-cutting measures were paramount to the construction of such large structures. For example, most large walls would actually be two thin parallel walls, filled in with mortar and grout. Of course, these would not be strong enough to stand on their own, so the cathedral would be supported by a skeleton of fully-stone columns. These columns would often be left standing exposed on the inside or outside of the cathedral, called an arcade, which would then lend their support to the roof and walls via flying buttresses. The countless arches which went into the overall design of the structure were constructed with removable wooden templates. The centerings, as they were called, would be moved into place in between the columns once they were complete. Stones would then be stacked on top of the supports until the keystone was placed and they could hold their own weight, at which point the centering could be removed and placed to begin construction of the next arch.
Making sure that the thousands of stone blocks which went into the construction of the cathedral fit perfectly was no easy task. However this perfect was of the utmost importance, as if it didn’t all go together seamlessly, well, I’m sure you can imagine the disaster which would follow. Typically large vertical substructures would be assembled horizontally on the ground beside the cathedral, to ensure that everything interlocked as it was supposed to, before the large blocks were hoisted into their proper places and mortared together.
In terms of the hoisting, scaffolding was not quite up to OSHA standards back in the day. Wooden pools lashed together with rope, and platforms made of interwoven twigs were about as good as it got. For most cathedrals, there simply weren’t trees tall enough to form sturdy supports for scaffolding. As a result, design choices were made to allow for scaffolding to be temporarily built using the walls as support structures. In some cases, timber was used in the permanent structure, in which case logs would be imported from as far away as Scandinavia in order to get wood in the right dimensions.
Moving massive stones up off the ground on these flimsy wooden structures was no easy task, however some clever engineers figured out ways to make it feasible. The medieval windlass consisted of two dudes inside a hamster wheel comically (though dangerously) walking inside to turn an axle. A rope secured to this axle would then lift the heavy weight. Tom Scott did a video on a recreated “treadmill crane” that they have in Guédelon, France, where a team is constructing a castle using medieval techniques. In my opinion, more kids should aspire to be castellogists when they grow up.
Perhaps one of the most striking features of a cathedral are the massive stained glass windows. Typically showing biblical stories pictographically, the designs would be fully sketched out 1:1 on a whitewashed table, where all of the necessary glass and metal framework would be assembled. Windows could be as large as 40 feet tall, but always consisted of smaller subsections of metal frames which were no more than 30 inches square, and individual pieces of glass were typically no larger than three inches wide. As with the stone structures, once the whole window fit together, it would then be disassembled and moved into its proper place.
The roof of the structure was constructed in a similar manner to the arches, with light stones being placed on top of removable wooden supports. It could take years for the mortar to dry fully enough for the supports to be removed, but after enough waiting, the whole thing would be capped off with a four-inch layer of concrete. It was then smoothed over with plaster so that it would be pleasing to God’s eye, as no human on the ground could ever see such detail, and drone promotional videos weren’t a thing yet. For steeper sections of the roof, a nice and safe lead paneling was applied liberally (they also used lead in the stained glass window frames).
Once the finishing touches such as bells, statues, and interior decorations were added, the cathedral was finally complete. The entire project could take up to 100 years, in many cases outlasting the people who began it. The structures inspire to this day, and will continue to do so for centuries into the future.
Sourced mostly from Cathedral by David Macaulay. If you have a fun fact or topic that you would like to be brought to light, email me at qhoop@reed.edu!