© Luxigon

Architect: REX
Location: Incheon, Korea
Client: Songdo Landmark City (SLC)
Program: Residential towers with a total of approximately 2,000 units, community facilities, retail, and underground parking
Area: 342,900 sqm
Project Status: Completed Concept Design
Landscape Architect: Bureau Bas Smets
Executive: HYUNDAI Architects & Engineers; SAMOO Architects & Engineers
Key Personel: Adolfo Albaisa, Haviland Argo, E. Sean Bailey, Keith Burns, Nicolas de Courten, Rob Daurio, Jeremiah Joseph, Hui Lee, Katharine Meagher, Clinton Miller, Roberto Otero, Michelle Petersen, Joshua Prince-Ramus, Jacob Reidel, Nikolas Rychen, Tal Schori, Hala Sheikh, Nuo Xu
Consultant: Magnusson Klemencic Associates

REX was asked to design a residential complex in Songdo Landmark City in which every apartment offers direct southern exposure, cross-ventilation, and views. However, Korean zoning guidelines and local building practices typically produce towers that fail to provide these three key, locally-prized amenities. Furthermore, prevailing site strategies carve up the open space such that the result is not the often-advertised “Towers in a Park,” but anemic “Towers in a Yard” instead.

Block A4 challenges conventional Korean development practices to provide the key amenities within each unit and a true publicly-accessible park at grade. Korean towers typically have four or more units per floor. As a result, many apartments have limited direct light, no southern exposure and poor cross-ventilation.

Courtesy of REX

By splitting a single tower with four units per floor into four separate towers with only one unit per floor, the resulting super-slim building type maximizes direct lighting and guarantees southern exposure for every unit, increases cross ventilation, increases views, and even increases ambient light.

In conventional four-unit towers, the structural core occupies the center of the floor plate. The small floor plate of a super-slim tower allows the structural core to become the tower perimeter. The resulting stiffened structural tube opens up the interior and eases space planning.

Surprisingly, the structural tube can be 50% perforated, as long as all openings are located to maintain continuous load paths and to minimize lateral displacement. The dynamic behavior of the perforated structural tube is well within acceptable standards.

© Magnusson Klemencic Associates

In Korea, gang-form construction is commonly used for the exterior walls and columns. Traditional concrete construction is used for interior bearing elements and floor plates.

As an alternative, by using Jump-up/Jack-down construction to build the perforated structural tube, it becomes possible to reduce the project build time by 63% compared to conventional gang-form construction methods.

The façade is designed to combine flexibility with a consistent image. Depending on the preferences of individual apartment owners, any given façade opening can be finished as a floor-to-ceiling window, an open-air balcony, or—with the use of a specially-designed manually operable window—an interior living space during cold months and a balcony during warm months.

The lobby of each tower occupies a double height space accessible from both grade and parking levels and provides daylight to below-grade community facilities.

Local zoning guidelines dictated that any windowed façade be separated from a facing neighboring building by a horizontal distance equal to the building’s height. In the case of a typical four-unit tower with windows on all sides, this rule would generate vast empty zones between towers unconducive to ground-level activity or community.

© Luxigon

However, as all of the super-slim tower’s services (including the single stair and elevator required by local code) are located to one side of the building, a single windowless façade per tower significantly increases site plan flexibility while maintaining privacy and views for the residents.

The prevailing Korean superblock site strategy carves up the open space at grade with a tangled network of hardscape paths. The resultant pockets of green space are residual in character and more akin to yards than park.

By organizing the landscape at grade into a series of continuous bands, SLC Block A4 presents an alternative site strategy that will provide an open, active, pedestrian-friendly park.

© Luxigon

All vehicle access and parking is placed below grade, and the towers are sited within the parking grid. At ground level, the towers create a diverse hierarchy of open spaces.

The primary pedestrian routes are consolidated into only four hardscape paths, avoiding a patchwork that would, on a site of this size, disperse and diffuse activity and divide up the green space.

Liberated from unnecessary interrupting paths, a genuine park of diverse landscape bands¬—capable of hosting a variety of public outdoor activities—is created across the site.

By threading the softscape and hardscape bands through a forest of super-slim 55-story towers with only one unit per floor, the resulting design for Songdo Landmark City Block A4 transforms Korean high-rise residential development.