January 14, 2010
Flawed Building Likely a Big Element
By HENRY FOUNTAIN
Engineers and architects who have worked in or visited Haiti say that substandard design, inadequate materials and shoddy construction practices likely contributed to the collapse of many buildings in the earthquake that struck Tuesday.
Cameron Sinclair, executive director of Architecture for Humanity, a nonprofit design group based in San Francisco, said he was “horrified” when he visited Port-au-Prince and Gonaïves last October to assess the quality of construction there.
Mr. Sinclair said that design and construction were far worse than in other developing countries he had visited. “In Haiti, most if not all of the buildings have major engineering flaws,” he said.
Most houses and other structures are built of poured concrete or block, there being very little lumber available due to mass deforestation, said Alan Dooley, a Nashville architect who designed a medical clinic, built of reinforced concrete, in Petite Rivière de Nippes, a fishing village 50 miles west of Port-au-Prince.
Concrete is very expensive — much of the cement for it comes from the United States, Mr. Dooley said — so some contractors cut corners by adding more sand to the mix. The result is a structurally weaker material that deteriorates rapidly, he said. Steel reinforcing bar is also expensive, he said, so there is a tendency to use less of it with the concrete.
Building codes are limited or nonexistent, so columns and other elements made from concrete are often relatively thin, designed without proper margins of safety. “We would double the design strength, just to give it a factor of safety,” Mr. Dooley said, referring to practices in the United States. “There they’d design it to what it would hold.”
Concrete blocks are often substandard too, said Peter Haas, executive director of Appropriate Infrastructure Development Group, a nonprofit organization that is working on several projects in Haiti. Many of them are made in small batches at people’s homes, and the quality can vary. “When you’re buying blocks at the store you really have no idea of where they’re from,” Mr. Haas said. “And all it takes is for the block that was made at home to collapse.”
When builders in Haiti do take disasters into account in their designs, their most recent experience has been with hurricanes, the last major earthquake having occurred two centuries ago. “Newer construction has been developed to withstand hurricanes, not earthquakes,” said John McAslan, a London architect who has studied Haitian buildings, working with the Clinton Global Initiative. “If you engineer for one you’re not necessarily covering the other.”
Mr. Dooley said that his original design for the medical clinic called for a steel roof, but that was changed to a reinforced concrete one to better withstand hurricane-force winds. The building survived the earthquake with apparently little damage, he said.
But many other concrete roofs presumably collapsed, adding to the loss of life. Mr. Sinclair said he had seen houses where builders put concrete roofs on top of low-grade blocks. “Then it just pancakes,” he said.