CHANGSHA, China — The 202-story “Sky City” project is not the tallest building on the drawing boards around the world. That distinction belongs to the Kingdom Tower, a project in Jeddah, Saudi Arabia, that is to be 532 feet taller — the first building to reach a full kilometer.
But while work on the Kingdom Tower’s foundations is further along than work on Sky City, the Saudi skyscraper is not slated for completion until 2019 — five years after Sky City is to be finished.
Sky City’s much faster building schedule underlines how different it is from most skyscraper projects. The Broad Group, an air-conditioning manufacturer that has moved into construction, wants the building to be not only the tallest jumbo skyscraper when it opens but also the most rapidly built.
The company will build it as if it were a house in the American suburbs — with prefabricated modules.
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Dennis Poon, the chief structural engineer for some of Asia’s tallest buildings and the vice chairman of the Thornton Tomasetti engineering firm in New York, said erecting a 202-story building from prefabs was an extension of a global trend in the industry in the last few years.
Many companies are using factories to make larger and larger pieces of buildings; Poon said an ambitious Chinese-owned hotel project that he was helping to build in the Bahamas used prefab bathrooms.
Relying entirely on modules means the 4,450 apartments will have little flexibility later to be turned into hotel rooms or offices if these should prove more profitable, he said. Assembling an entire building out of modules also considerably limits the flexibility of architects to create distinctive shapes that can symbolize a city.
“Feasible? Yes, of course, but you get what you get,” Poon said.
David Scott, a recent chairman of the Council on Tall Buildings and Urban Habitat, a nonprofit group in Chicago, agreed the project was feasible in engineering terms. China has much stricter standards than the United States for earthquake resistance, he said, and the lightweight, modular construction of Sky City will help it withstand quakes.
But while the exterior walls of the building will be very heavily insulated against the weather to save energy, the thin, lightweight floors may not block enough sound traveling up and down through the building.
“You will have a challenge of hearing the people above and below you,” said Scott, chief structural engineer at the Laing O’Rourke engineering firm in London. “I don’t think it would meet market expectations here.”
International experts question whether Sky City can be built as fast as the Broad Group promises. Keith Brooks, the director of global property at EC Harris, a global consulting firm that is one of the project managers for the Kingdom Tower in Saudi Arabia, predicted that hoisting large modules high into the sky for a 202-story building would prove more time-consuming and difficult than Broad expects.
Large components tend to catch the wind like sails while they are being lifted by cranes. “I’m sure you can design the modules. The question is getting them up there,” Brooks said.