One building, many lives

Modern high-rise development is redefining how cities grow, function, and serve residents in the 21st century. As urban populations increase, cities are shifting from horizontal expansion toward dense, mixed-use vertical environments that integrate residential living, wellness services, and retail, hospitality, and office space within a single vertical framework.

For developers and architects, mixed-use structures spread land cost, intensify use on small sites, and command higher rents or sales prices, points out Scott Ziegler, AIA, of Houston-based Ziegler Cooper Architects. Ziegler has spent 25 years studying urbanism and high-density living.

While mixed-use stacks have myriad benefits, making their economics and designs feasible requires a lot of coordination. The following three projects show where bottlenecks occur, what architects have learned, and how the mixed-use strategy turns the modern urban building into a carefully negotiated stack of economics, circulation, image, and infrastructure. 

415 Colorado is a 48-story tower that sits on a 20,000-square-foot site in Austin’s urban core. The program combines six floors of office space with 24 floors of apartments. To shape this mixed-use building and make it work, Ziegler says his clients asked to stack the program elements vertically. 

There are 12 floors of shared parking, 328 residential units, 110,000 square feet of office space, and 3,500 square feet of retail. “The office component was placed in a separate condo association capital stack, where development partners personally guaranteed that portion of the loan,” he says. That capital structure was small enough for the sponsors to absorb risk themselves, which unlocked the rest of the project’s funding arrangement.

While the economics were challenging, the most difficult part of the design was reconciling how each use has its own program requirements inclusive of structural, mechanical, and vertical logic. For example, apartment residents want their elevator banks separate from offices tenants’ elevator banks. Additionally, residents desire individual thermostat controls for their apartments, with kitchen and bath exhaust routed separately for each unit. Offices run on zoned commercial HVAC systems with large air handlers on each floor, while retail spaces have their own mechanical systems.

The garage, too, was a puzzle. The final design resulted in a helix garage featuring six laps up, complemented by a reverse-direction helix down on a different ramp. Tolerances were tight, and everything had to be modeled floor-by-floor, inch-by-inch into a 3D BIM model for the contractor to build it.

To craft a cohesive design for the different stacked uses, Ziegler overlayed an aluminum-clad curtain wall system across the entire facade from top to bottom, capturing the garage floors so they disappear, and carved a loggia at the amenity floor that opens to an outdoor pool terrace with a bar and grill.

Ziegler likens his firm’s role as “the conductor of the orchestra, where we select the specialty consultant team best suited for the project and coordinate our design team with weekly owner-architect-contractor meetings”. He cautions that “project review and approval process with municipal authorities is painstakingly meticulous, and 415 Colorado’s site development approval took nearly 18 months.”

The Bellemont is a 13-story residential building with 4,000 square feet of street-level retail, roughly 11 floors of apartments (with one condominium per floor and some duplexes), and amenities tucked below grade. Completed in December 2023, the structure references French-style New York City mansions from the late 19th and early 20th centuries. It is a hand-laid limestone building commanding the corner of Madison Avenue and 86th Street. 

A critical urban design puzzle for RAMSA partner Paul L. Whalen, FAIA, was that NYC zoning requires retail space on the ground floor of avenue-facing residential buildings, but high-end residential entrances must feel separate from retail areas, Whalen says. On this site, there was no quiet side street to accommodate the residential entrance. 

To create a separate identity for the residential entrance, Whalen distanced it from the nearest retail storefront with 15 feet of articulated stone wall treated with strong rustication, a raised cornice, and French curves to frame the entrance within a classical pavilion that rises above the retail band. A large keystone, tall custom sconces, a bronze door, a canopy with bronze supports, and planters all signal “grand residence,” not shopfront. Once people enter the front door, Whalen says, “they are isolated from the experience of the adjacent retail. Though the shops are high quality, a close relationship to them in the New York market may feel too hotel-like.”

Having retail on the ground floor of a high-end New York City condominium can be a fraught proposition. “Condominium sales are driving the value of the project, so even with great retail, the desire for privacy at a residential entrance must be accommodated. Once privacy is achieved, good retail will help enhance value by creating convenience and a lively, charming streetscape,” notes Whalen. 

This aspect is prone to pitfalls, he adds. “It’s easy for the front door to not feel private enough, or to feel like it’s too commercial, or that you’re too close to traffic. You have to use the appropriate architectural tools to create clarity at street level and a happy marriage of retail and high-end residential.”

Still in its marketing phase, The Summerhill is a 32-story high-rise that includes 60 residential units and 20,000 square feet of office and retail space, located at street level. The building couldn’t have conventional underground parking because of the relatively small site and existing heritage buildings. Instead, the design team kept the parking entrance to the left of the entry and installed an automated parking system that is below grade and goes down four stories.

At The Summerhill, Modernist Peter Clewes, principal of architectsAlliance, had to navigate the retention of a heritage façade along with designing a contemporary tower that includes residential units, office space, and a garage on a small site beside a major rail corridor. 

The Summerhill sits on Yonge Street, which had been lowered in the early 20th century to avoid a level crossing with the railroad. The buildings on it “are very curious looking because it’s like they’ve been lifted in the air,” Clewes says. In addition, the buildings were not well cared for, but the city required them to be kept. “We have to somehow rehabilitate the buildings, re-proportion them so they don’t look like their pants are too short, and we need to work within the style in which they were built,” Clewes says. 

As for the mixed-use aspects, the hardest coexistence problem is giving each section a clear sense of identity without undermining the others. This is particularly true with the residential identity of the project, Clewes says. “Residents want to feel that their building is special and stands apart from any other use within the project.” 

There were challenges, too, in the structural system. Typically, offices and retail need long-span spaces with a simple grid of columns to give maximum flexibility for tenant changes. Residential units need smaller, individual rooms that rely on more structural elements like walls and columns. “Transferring loads from one structural system to another can be very difficult,” Clewes says. 

He cites a similar problem with mechanical systems. “Offices tend to be ‘cooling dominant’ where residential tends to be ‘heating dominant’,” Clewes says. For rooftop mechanical equipment, designers must also navigate questions of ownership, control, and access. Separate office elevators and a separate mid-level mechanical room addressed these hurdles.

Buy-in from all

Despite solving equations for cost, engineering and design, an architect’s vision can’t come to fruition without buy-in from the community. For instance, with The Summerhill, Clewes says, there was a long process of negotiation and engagement with the neighbors and the city’s planning department. “You have to be very patient, good listeners, and good mediators to really engage in that process.” 

As Ziegler puts it, “at its core, the broader question facing architects, planners, developers, and civic leaders is not simply how to build taller buildings, but how to create vertical mixed-use buildings that foster community, resilience, accessibility, and long-term quality of life.”

Stacey Freed is a freelance writer focusing on architecture and design. She lives in Western New York.