The Bowls Project uses an ancient building technique— masonry tiles built into soaring arches—with no steel beams or rods needed to support them.
How does it work?
It doesn’t seem possible that the unsupported tiles could stay up all by themselves in their long, gentle curves. But this vaulting—unlike the Roman variety make of thick stones—can support heavy loads by itself.
Guastavino devised two innovations to accomplish these self-supporting vaults: tiles that are thinner and lighter than heavy brick. And, in the second innovation, fast-hardening Portland cement instead of traditional mortar.
Typically, three tiles are cemented on top of one in rapid succession, creating what looks like one tile, but is really a laminate of the three tiles. “You would have to cut them open to see the three tiles,” Ramage said.
Each tile is created and--sometimes in a herringbone pattern--are fastened to the next with the quick-drying cement. The tiles support themselves as the cantilevered arches grow out into space. So strong is the structure that workers can stand on what they’ve build on the next day as they work to extend vaulting.
The system makes the vaults much light than others. “If you know what you are doing,” said Michael Ramage, architect of The Bowls Project, “you can mix just enough for one tile and it sets in 20 seconds. Then the next layer is added.
How did Michael Ramage make The Bowls Project seismically safe?
Traditionally, unreinforced masonry can’t be used it earthquake zones, for fear it will collapse at the first tremor.
For The Bowls Project, Michael Ramage has made two innovations to the classic design—innovations that he hopes will lead to adopting of the inexpensive masonry vaulting one day in underdeveloped countries in earthquake regions.
First, he added strengthening layers of a unusual composite material-- a geotextile— between the tiles to add additional support. As each three-tile layer is built, the order is tile, textile and mortar for the first layer; then tile, textile mortar for the second layer, and then a final tile on top.
Second, he found a lighter material for the tiles—a concrete so light that it floats in water. These tiles are cut with an ordinary bandsaw from big blocks of the aerated concrete, normally used in buildings. Each 8” x 4” tile is 1.25 inches thick.
The structure will be tested by vigorous assault by earthquake-sized forces in machines operated by San Francisco building officials to make sure it is earthquake resistant before the first person enters.
Michael Ramage has a degree in architecture from The Massachusetts Institute of Technology, and now teaches at Cambridge University in England. He designed the masonry vaulting for a museum in South Africa, the Mapungubwe Interpretation Center, winning the World Architecture of the Year award in 2009. It is made from tiles created with local soil, and cement. His He also designed the domes for the Pines Calyx, the first Guastavino-style vault to rise in the United Kingdom.
by Anne Eisenberg
Last updated June 15, 2010