The “Growing Rowhouses” design approaches the frequently unused and neglected rear yards of a block of traditional rowhouses as a single lot. Kim’s modular system uses an 18-ft grid in keeping with average rowhouse lot width. The height of the new rowhouses can change according to allowable zoning.

This strategy requires minimal foundations to leave the existing rowhouses untouched. That’s where structural steel came into play. Steel cables on either side of the central structural core stabilize the building’s lateral movement.

“Steel is the most viable solution to achieve the minimal touchdown in the centerline of the  blocks,” Kim said. “A prefabricated, modular construction system taking full advantage of steel’s unique potential to facilitate economical, rapid erection--and steel’s unique recyclability and circular supply chain add an additional layer of sustainability while preserving the existing rowhouses.”

The new, vertical community consists of duplex units with semi-private outdoor yards. Outdoor communal spaces include a rooftop terrace and running track. Curved hollow structural sections create a cohesive look across external stairs, roof structures, and trellis extensions--a detail that also allows for mass production.

“We think it’s a robustly developed proposal with a timely architectural premise and a clear idea about how and why steel will be used to support the concept,” Marani said. “It has a well-considered implementation strategy, including coordination with zoning and planning constraints, market demands, and erection efficiencies. It also fits neatly into new approaches to zoning within the Department of City Planning, specifically the larger City of Yes policies that are being rolled out.”

The Growing Rowhouses concept was one of three visionary designs that made it to the final round of the 2025 Forge Prize, in which the designers presented their refined concepts to the jury in a YouTube livestream that is now available as a recording.