My nephew's cross-barrel vaulted ceiling
Czechia, July-September, 2010
My younger nephew is a civil engineer/architect, and his dream was to build
a brick vaulted ceiling similar to those of old churches.
He was designing his future house himself, and so he used in his design a
cross-barrel vault for the ceiling of his basement study/recreation room.
He started building his new house this spring, and the work on his vaulted
ceiling had began just days before I arrived there on July 20.
To build a larger size vaulted ceiling, at first one has to construct a usually wooden scaffolding of perfect cylindrical shape which would support the layer of bricks before it can be closed at the crown. The scaffolding will stay there till the end of the building process, till the roof of the house is finished, when everything hardens well, and settles down. My nephew believes that when that time comes next year, he designed the scaffolding support system so that he would actually be able to lower the scaffolding onto the floor of the basement, and salvage the wood used for scaffolding, without being crushed, without having to burn the scaffolding as was often done in case of medieval vaulted-ceiling churches. We'll see next year how it goes.
To build a single vault (nave) is not that difficult, but he complicated the task by designing three shorter cross barrels that will go perpendicularly from the main barrel to three semicircular windows, that would provide the lighting of the only partly subterranean basement. The difficult part is how to join properly these four cylinders, both when building the supporting scaffolding, and when constructing the brick arches themselves.
He hired two professional carpenters to build the scaffolding. When I arrived, they already had a part of the main cylinder (see the first two photos below). It took them another two weeks plus to finish the job (each week, they usually worked for about 3 full long days on and around the weekend, and 3-4 more afternoons/evenings after their more regular job).
Then came a bricklayer, who initially spent some time consulting old books how this job should be done properly. Every brick along the lines where each of the two perpendicular cylinders are joined, had to be cut by his helper in usually two different planes to fit tightly with all the adjacent bricks. They used electric stone cutters to do this (traditional, usually not so precise method to "cut" a brick was to tap it with the tip of a hammer along the line where you want it to break). Once they figured out the values of the cutting planes angles, the job started to progress faster. Because they were not available on continual basis, it still took over a month to build the brick arches.
Traditionally, that was usually the end of the process, because not much load was expected to be put on such a ceiling. Nothing in churches, and maybe some hay in old country houses. But he wants to have another storey on top of it. So he was putting a layer of reinforced concrete on top of bricks. First we placed a mesh of iron re-bars on top of the bricks, held a few centimetres above the bricks by small plastic spacers - to be roughly in the middle of the concrete layer. Then he ordered a truck of specially formulated thick and fast-drying concrete. It was interesting to work with it, as it did not flow at all and could be molded almost as Plasticine so one could easily make of it a layer that followed the curved surface of the bricks. But it needed to be worked up as fast as possible, and so I was also helping with it on my very last day there.
After I left, they still had many warm weeks (albeit interspersed with some cold and rainy weather), and so my nephew still managed to fill the spaces between the arcs with a lightweight filling mixture (styrofoam bits, porous ashes, ...), pour a flat concrete slab on top of it all to have a flat floor for the next storey, and at the very end of November he even managed to finish the building of the full height of exterior walls (no photos yet) before they were finally snowed in with the most of Europe.
As may be visible in the photos, old recycled bricks were used for the vaulted ceiling. Good bricks can actually be recycled many times and used in many consecutive houses for several centuries. The only problem with that is that before re-use one has to clean them of all the old mortar, which usually is a tedious and dusty work, which I tend to dislike. Most often axes are used to scrape old bricks. We also tried to use for this metal brush-like scrapers for horse grooming, which worked quite well, but nowadays new ones are hard to get by.
