NOMAL subtracts and adds geometries to maximize space at ‘concrete sandwich’ in seoul

nomal completes concrete sandwich in seoul

NOMAL’s Concrete Sandwich addresses the evolving challenges of Seoul’s real estate market, as new architectural developments often play a balancing act between maximizing floor area ratios, minimizing costs, and navigating complex regulations. The design, marked with additions and subtractions in geometries along the concrete volume, is within a creative renovation of an existing structure, merging volume maximization with cost-effective construction.

The project responds to the long-standing trend in Korean architecture to push the limits of floor area ratios within tight urban confines. Originally constrained by road diagonal and north-facing sunlight restrictions, changes to regulations allowed the pyramid-shaped building to expand vertically to three floors, with a terrace and sloping roof on higher levels. By retaining much of the existing core and structure on the west and south sides and strategically rebuilding on the east and north, the Korean practice created additional usable space with a cost-efficient steel framework. Terraces, enabled by utilizing 1 meter eaves exempt from floor area ratio calculations, further optimized space in this ‘addition game.’

a concrete glaze conceals steel details

On the other hand, the form was a ‘subtraction game.’ Where possible, NOMAL tried to simplify by using the minimum elements and ready-made products. Semiconductor-combustible urethane panels (sandwich panels) were used as the prefabricated construction method’s exterior walls to meet the insulation standards while minimizing costs and streamlining the process.

The exterior walls use urethane sandwich panels for insulation, while exposed rainwater pipes and corrugated steel sheets simplify maintenance. Terraces have been positioned to rest on pedestals for better drainage and faster construction. To satisfy the client’s request for an exposed concrete aesthetic, the architects also applied a concrete glaze over the panels, achieving the desired look without costly materials.

While the design generally mimics a concrete structure — with the application of concrete like a porcelain glaze on top of the sandwich panels — subtle details reveal its true composition. Exposed steel beams peek through gaps in piloti columns and the interior ceiling, offering playful nods to the building’s reality. These ‘easter eggs,’ while subtle, inject humor into an otherwise restrained facade, a feature the architects feel that only their contemporaries might appreciate.

The windows were also minimized to the extent necessary for lighting, ventilation, and firefighter entry, prioritizing the criteria of reducing interference with neighbors on the adjacent land. For the design team, renovating the existing structure posed inherent challenges, such as managing aging variables that increase costs disproportionately in smaller buildings. Despite these constraints, NOMAL transformed the space into a comfortable and efficient environment at a relatively low cost, exemplifying the adaptability needed in a time of notable economic and societal shifts.

project info:

name: Concrete Sandwich
architect: NOMAL

location: Seoul, Korea

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