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Published on Friday, 07 Mar 2014
The Liaoning Province Meteorological Station in Shenyang topples during a controlled demolition. While explosives are rarely used to demolish buildings in China – and even rarer in Hong Kong – local demolishers are equipped with the skills to use them.
Photo: Reuters
Choy Kin-kuen

Demolition is highly skilled work learned mostly on the job

It is generally understood that destruction is easier than creation. But in the construction profession, taking down a building can often take more effort than putting it up in the first place.

Professor Choy Kin-kuen, immediate past president of the Hong Kong Institution of Engineers (HKIE), points out that demolition is a highly professional job which only industry veterans can handle. "Currently there is no structural training for engineers in demolition. Some universities offer a master's degree that teaches demolition techniques, but most of the skills have to be learned on the job. Experience is a crucial factor in determining if an engineer is able to get the job done," he says.

Construction of a building is basically a bottom-up process, starting from the ground and working upwards. Demolition, on the other hand, is not the straightforward, top-to-bottom removal action many would expect.

"There are many factors that engineers need to take into account during demolition. The first is how it will affect the buildings around it. The situation is especially tough in Hong Kong, where buildings are so close to one another. The engineer has to know the structure of the building really well in order to demolish it. You have to know how to build it if you are to demolish it," Choy says.

Choy adds that some buildings may employ a "hanger" design, where support does not necessarily come from the bottom, and engineers must take extra care when planning demolition. If the engineer demolishes the building level by level from the top, it may collapse. If it is a hanger design, it is necessary to carry out support work at the bottom before demolishing the levels above.

There is also a risk of floors collapsing if support work is not done properly. A lot of heavy machinery is employed in demolition and sometimes floors are not strong enough to hold these machines.

"Another risk is debris accumulating on floors causing them to collapse. Demolition is inevitably a more risky and complicated job than constructing a building. It is important for engineers to pay attention to employing adequate and sufficient safety measures in a project, and this is even truer in a demolition project," Choy says.

Redevelopment projects have been a major driving force for the local construction industry. Many old buildings are taken down to provide more land for redevelopment, making engineers with experience in demolition a hot commodity.

However, due to its unpleasant working nature, the sector has a hard time attracting talent. Thomas Wong, managing director of YSK2 Engineering, a local contractor specialising in demolition, thinks the government and local organisations should be leading the way in ridding demolition of its negative label.

One solution, he says, is better education. A few years ago, Wong published a book, the "Explanatory Handbook to Code of Practice for Demolition of Buildings", in collaboration with the Buildings Department, to give engineers in-depth knowledge of demolition. "People are scared of the unknown," he says. "If they learn more about the risks, and ways to avoid them, they will no longer consider it a dangerous job."

Wong thinks that the government can do more to manage the demolition discipline. "The law requires an authorised person [AP] and a registered structural engineer [RSE] on a demolition project. There are no standards to determine how knowledgeable the APs and RSEs are about demolition. Requiring them to have a certain level of experience will enhance the professionalism of the discipline," he says.

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