They are so thin that it's hard to believe that they stand up.
Have you been in the Oyster Bar in Grand Central Station? Or the Boston Public Library? Then you have been in a Guastavian vault, a dome built by Rafael Guastavino and his family. He brought the Catalan or Timbrel vault from Spain and built many in the USA. They are ingenious, very thin structures that are built without reinforcement, just the bonding of ceramic tiles together into thin, shallow arches. Kris at Low-Tech Magazine described them in the definitive post on the subject:
The timbrel vault does not rely on gravity but on the adhesion of several layers of overlapping tiles which are woven together with fast-setting mortar. If just one layer of thin tiles was used, the structure would collapse, but adding two or three layers makes the resulting laminated shell almost as strong as reinforced concrete.
Timbrel vaults are also known as Catalan vaults, because it is thought that they were invented in Catalonia. Not far down the Mediterranian coast from Catalonia is Villarreal, where Fernando Vegas and Camilla Mileto have designed a Pantheon (defined as "a building in which the illustrious dead of a nation are buried or honored"), but which in North America we would call a mausoleum. This one is for the Soriano – Manzanet Family, who may or may not be illustrious, but certainly have style.
According to the V2.com press release,
Special 3D programs were required to design the pantheon and the final solution was only agreed on after 23 consecutive variations aiming for optimum aesthetic and structural results. All the curves in the pantheon were produced using catenary profiles. These curves are incredibly difficult to express mathematically and graphically to successfully optimise the construction’s overall structural operation.
Close to 20,000 handmade ceramic tiles were used in construction following tests to establish the type of clay, fuel and flame, texture, durability and aging tests. The size and thickness, both dependent on the curves of the pantheon, and the necessary weight were calculated for the three ceramic layers to compensate for the effect of wind suction.
Timbrel vaults don't need a lot of expensive formwork, usually just a bit of light moveable stuff for the first layer. But these vaults were designed without any formwork at all.
The vault is comprised of four interlinked hyperbolic paraboloids and is very light yet incredibly resistant because of its curves. Formwork was not required and only some metal guides were used to ensure curvature was guaranteed at all times.
It is a very light structure, coming in at 12.5 tonnes; they say that a conventional masonry pantheon weighs between 15 and 20 times as much. It was built with only tiles plaster and white cement, and no reinforcement. "Nevertheless, the pantheon vault is designed to withstand possible earthquakes given the rigid curves and the addition of fiberglass rods at the springings to absorb shear force."
It is sort of ironic, using such an efficient and light structure for such a silly function as a family mausoleum/ pantheon; it would be more exciting if it was something useful, like a tapas bar. Perhaps architects will be inspired to use this incredible technology for a more lively function.