Delivery of the future-tallest building in the Republic of Korea is a family affair—or the closest thing to it. Lotte Group, the owner-developer of the planned 555-meter Lotte World Tower in Seoul, is bringing back the master-builder model for its first supertower by keeping project management, construction management and general contracting under its own roof.

"This is the first time in the world this is happening" for supertower delivery, says Y K Kim, executive director of the CM division of South Korea's fourth-largest family-run conglomerate, or chaebol. Kim should know. He is a veteran of supertower construction, mostly working for Samsung Corp., also a chaebol.

Kim is a big fan of Lotte's delivery approach for its $3.5-billion Lotte World 2 development, which includes the 325,000-sq-m multi-use skyscraper and a low-rise development. On the project, differences are resolved by consensus. "There are no more arguments, no more conflicts," says Kim. "We are one family."

Decision-making is faster and easier. The fast-tracked construction is less wearing because tension over inevitable design refinements is eliminated. Tendering happens a lot less frequently, says Kim.

The delivery approach leaves the Lotte team more time to devote to the complications of building the supertower—a form evocative of a Korean calligraphy brush. About one-third the way up the tower, the form begins to taper gradually.

The tapered section and its consequent slopes are presently the project's biggest headaches, says Kim. Every floor plate is slightly different, which means adjusting formwork at every floor. Structural elements slope in either one or two directions, complicating their construction. Curtain wall units come in slightly different sizes. Repetition is not the name of the game.

Fifth Tallest Under Way

Lotte World Tower, once called Lotte Jamsil Super Tower, is the fifth-tallest building under way in the world, says the Council on Tall Buildings and Urban Habitat. Chaebols, other than Lotte, have built the world's tallest towers. Yet the tallest building in Korea is the 308-m North East Asia Trade Tower at the Songdo International Business District (see p. 32).

The Lotte tower is just coming out of the ground. If finished by October 2015 as currently scheduled, the 123-story tower would rank as the seventh tallest of the world's eight supertowers over 500 m. The tallest is the 828-m Burj Khalifa in the Arab emirate of Dubai.

Since 1989, Lotte's founder and general chairman, Shin Kyuk-Ho, weighed 10 designs by three other architects before selecting the current design by New York City-based Kohn Pedersen Fox Associates PC. KPF's associate architect is a local firm, BAUM.

The tower's curved, elongated pyramidal form is derived from the building's six stacked occupancies, each with its own optimal floor-plate size, says Richard Nemeth, a KPF principal. The design calls for a building that is symmetrical around the diagonal axis of its base, a 70-m-square in plan. Opposite corners are either rounded or notched. Notches increase in size from 1 m at the base to 10 m at the top.

Slopes start and floor plates begin to morph above the office stack, at floor 42 in the "officetel" stack. An officetel is a home office peculiar to Korea because zoning otherwise prohibits commingled residential and commercial space. The taper continues through the hotel, premium office stack and observation levels.