Design firm JZA+D has announced the completion of its latest addition to a growing portfolio of innovative housing solutions that address missing middle housing. Located on John Street in Princeton’s Witherspoon-Jackson Historic District, the project transforms a single two-family residence on a 0.4-acre site into a two-structure, six-unit property comprising 8,300-square-feet total, all designed to harmonize with the area’s notable vernacular architecture. 

The reimagined site at 166-168 John Street is just one example of housing solutions that address the missing middle, a term that refers to the need for context-sensitive, multifamily solutions that promote sustainable, walkable, economically diverse neighborhoods, according to JZA+D founder and managing partner Joshua Zinder, AIA, LEED AP.  

“Missing middle solutions promote a more close-knit community, and support sustainable local economies,” says Zinder, a nationally recognized expert in multifamily housing. “When architects, developers, and municipalities work together to promote innovation, the results foster responsible increases in density and preserve the character of existing neighborhoods.”  

Missing middle approaches are also seen as adding appropriate density to existing residential areas while strengthening their appeal for current residents, according to groups such as the National League of Cities. As jurisdictions around the country strive to address the shortfall in available and attainable housing, experts in the field including Zinder are advocating for more effective missing middle solutions rather than large-scale midrise housing developments. 

A Historic Residence, Reimagined 

JZA+D’s solution for 166 John Street starts with an addition to the historic two-family home that expands the footprint of its two existing apartments, which have been completely redesigned inside. Below those units, a former unfinished basement has been converted into a new ground-floor apartment. Then, taking advantage of the site’s ample area, JZA+D’s team designed a new three-family residence, 168 John Street, set back from the roadway to maintain the historic streetscape. The site’s landscape design creates a new parking court wrapped by stone walls, minimizing impact on neighborhood streetside parking while harmonizing with the cultured stone veneer façades of the property’s two buildings, according to project architect Taylor Kinsey Toms, AIA, an Associate with JZA+D. At grade with the parking court, both ground floor apartments are fully accessible units and feature small patios. 

For the existing structure, the JZA+D team updated the exterior by replacing original exposed concrete block and stucco on the lower levels with stone veneer, and the wood siding above with more resilient fiber cement painted clapboard, to visually softens the architecture. A folded surface formed from metal panels creates outdoor rooms and slips out of the plane of the parking façade to create a green roof covered entry for the ground floor apartment.  This aesthetic is reflected on the new building, 168 John Street, its simple gabled form sitting atop the stone wall wrapping the parking court and harmonizing elegantly with the surrounding vernacular homes. The front balcony creates a covered entry for the lower apartment, and the same folded metal forms seen on 166 John cap the stairways to the upper apartments, helping to visually tie the buildings together. Inside, the mostly open-plan living spaces within the larger upper-floor units in each building are laid out with a great room feel to emphasize their spaciousness. For the reimagined existing home, rear outdoor rooms accessed through full-height glass doors provide additional seasonal living space.  Designed with sustainability in mind, all units feature ductless mini-split units for efficient zoned heating and cooling.  

Filling the Missing Middle 

The resulting housing complex at 166-168 John Street is the latest successful innovation by JZA+D adding much-needed housing options in historic Princeton neighborhoods. The firm recently won a SmartGrowth Award from NJ Future for their six-unit, mixed-income Nelson Glass House – the first development of its size to receive the honor – and the much-lauded, LEED for Homes Gold-certified 30 Maclean Street, a 10-unit residential building combining historic preservation and adaptive reuse across the street from 166-168 John Street. 

Former president of AIA New Jersey, Joshua Zinder has recently published a series of articles outlining how architects can help their local jurisdictions meet the required mandates under New Jersey state law for adding affordable housing units. In his firm’s pursuit of successful missing-middle solutions, JZA+D has explored a range of strategies, including: 

• Adaptive reusing buildings, including reinventing historic structures. 

• Adding residential floors above commercial uses in transitional-zone neighborhoods. 

• Creating upper-floor apartments in mixed-use buildings in town centers. 

• Building new multi-unit structures on existing single-family residential lots. 

• Designing pedestrian-permeable campuses for large-scale, multiple-structure, low-rise developments.  

“This latest work at 166-168 John Street is just one example of what is possible,” says Zinder. “The key to success for any innovation in design or planning is to communicate early and often with the surrounding community where new housing is proposed. It’s amazing what you can accomplish when you listen to people’s concerns in advance and make them part of the design solution.”