July 6, 2012

Column | Korky Koroluk

Sky is the limit for prefab construction?

China’s Broad Group, the company that gained international notice a couple of years ago by using prefabrication to put up a 15-storey hotel in just six days, is making news again.

At first, many people thought their first project was a just a stunt, and questioned how well the building would function. So the group did another project last year, putting up a 30-storey hotel in 15 days.

Now comes the big one: The company says it will build the world’s tallest building in nine months.

Called Sky City, the new structure will be 838 metres tall, eclipsing Dubai’s Burj Khalifa by 10 metres. Burj Khalifa, by the way, took six years to build, although there were a couple of pauses while more funding was obtained.

Preliminary plans for Sky City show 220 floors and a million square metres of floor space. There will be 104 elevators.

More than 80 per cent of the space in Sky City will be devoted to housing 174,000 people. The rest of the space will include a hotel, a school, a hospital, plus offices, shops and restaurants.

The secret, if there is one, is prefabrication of just about everything. Floors, ceilings, ventilation shafts — indeed all mechanical components —will be factory built and delivered to the construction site. All that is needed then is lots and lots of crane work, followed by crews bolting everything together.

Getting details on Chinese projects is always difficult, but apparently the developers of Sky City will borrow heavily from the engineering design done for the Burj Khalifa, and most of the mechanical and electrical components for Sky City will be built in the Broad Group’s own factory.

Once all those components are built, the company figures it can install them at the rate of five storeys a day.

The speed of the work is causing people to wonder how safe the jobsite will be, and how safe the finished building will be. It’s being built in the central Chinese city of Changsha, which is in a seismic zone, so how well will it withstand earthquakes?

Such questions were put to a company representative by a reporter for the Asian edition of the Wall Street Times, and the reply seemed somewhat dismissive.

The people who ask “do not understand our (construction) model,” Zhu Lingfang is quoted as saying. She said the company developed its techniques in response to the devastating earthquake that hit Sichuan province in 2008. As a result, Sky City will be able to withstand an earthquake of 9.0 on the Richter scale — a claim also made for its two earlier prefab projects. Not only that, but with 104 elevators, Zhu said the building could be evacuated in 15 minutes.

The Broad Group says the building will be energy-efficient, with a lot of insulation and quadruple-glazed windows as key features.

By prefabricating many building elements, there will be less waste, so there will be marked savings in the amount of steel and concrete used. The construction waste produced will be less than one percent of that produced by conventional projects.

We can all recall stories of building collapses in China that were blamed on the use of substandard materials or shoddy construction practices, so some folks are skeptical of this whole project. Will it be as good a building in real life as it is in the telling? We don’t know.

The central government has yet to give final approval, but that is expected next month.

There was an earlier proposal for a skyscraper 666 metres tall, but apparently it was rejected because the local government wanted the building to be the world’s tallest.

That’s why it’s easy to wonder whether this project might be, as much as anything, some kind of political statement.

Korky Koroluk is an Ottawa-based freelance writer. Send comments to editor@dailycommercialnews.com

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