National

Prime contractor behind leaning building ordered pilings of insufficient length

Kyodo

The designer and prime contractor of a leaning condominium building in Yokohama ordered a subcontractor to use 14-meter piles to build the structure, knowing that a demolished building at the same site had used 18-meter piles, a document obtained by Kyodo News showed Wednesday.

The findings strengthen the possibility of Sumitomo Mitsui Construction Co. having known the building would require longer pilings but ordered shorter ones for the subcontractor, Asahi Kasei Construction Materials Corp.

The October revelation of the leaning building has embroiled Asahi Kasei Construction Materials in a scandal and led to its admission that data had been fabricated for 360 out of the 3,052 projects it worked on over the past decade, including in piling works for the condo. The incident fueled public concern over the safety of buildings in general.

A 2005 blueprint obtained by Kyodo News showed that the demolished building, a Yokohama office of electronics maker NEC Corp., used 18-meter pilings in areas close to where 14-meter pilings were used to support the listing condo building.

Sumitomo Mitsui Construction has explained that the condo leaned because eight 14-meter pilings did not reach or were not driven deep enough into the 16-meter-deep solid-ground support layer beneath the building.

Denying that it was responsible for designing the piling work, Sumitomo Mitsui Construction has pointed to a construction mistake by Asahi Kasei Construction Materials as the reason for the tilt.

An official at Asahi Kasei Construction Materials told Kyodo News the company had not been informed about the demolished building.

There is a possibility the company “mistook” piling remains from the demolished building as solid ground, said the official.

A Sumitomo Mitsui Construction official, meanwhile, admitted the company knew 18-meter pilings had been used in the demolished building but said the piling work design for the condo was made based on “the results of a considerable number of ground surveys.”

The official refrained from commenting on whether the previous pilings had been pulled off or whether the company had implemented ground improvement work after demolishing the NEC building.

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