In the past, urban planners spent a lot of time coloring maps. Why? To set the rules for land use: Where will the housing go? The offices? The school? Two-dimensional thinking assigned one color to each parcel to guide which uses could touch each other and which uses needed a buffer.
If you played by the color code, you could then move on to designing your building. A significant amount of time and effort -- including plans, models, and financial analyses -- was spent arguing over the location and dimensions of the building, known as the building envelope, but not the mix of uses. The focus on the building envelope answered such questions as: How high? What materials? What form? How many floors? How much parking? All of these questions mattered. In some cities, this progressed to a discussion of building form as a whole, with form-based codes relating one building to the next and to the street, plaza, or waterfront those buildings faced.
It is time to break out the whole pantry of land-use ingredients.
But all too often those facing structures on the plazas do little to bring the people and commerce needed for a vibrant common ground, offering more of an empty pantry than a buffet of urban treats. Perhaps it's time to bring three-dimensional thinking to land-use designation, abandon the old model of segregated uses and build incentives for what I call "land-use sandwiches." A land-use sandwich would enable vertical stacking of different uses that multiplies the flavors we get out of any one bite of a city and nourishes us with diversity.
Whether it's a banh mi, a corned beef and Swiss, or an empanada, each sandwich has a myriad of tastes and a promise of discovery. The same could be offered by a lively, multilevel vertical sandwich of building uses, each with its own set of purposes and the potential to add spice or balance or nourishment to its neighbors.
The promise of the land-use sandwich comes from the freedom to break out of the standard mix of uses and adapt to the potentials of each city, district, or neighborhood. The planner, designer, or developer can offer more opportunity for businesses, arts, or educational uses at ground levels. Small business incubators might reside in upper levels of a building, with energy generators or food production on the roof. Housing can be used as a "wrapper" to hide unattractive building types -- such as parking structures. Each new land-use venture can be different and evolve as it responds to its surroundings and markets.Accommodating Diversity
While our cities have slipped into a monoculture of like uses and national chain stores, our communities are being enriched by a diversity of new people and lifestyles. Ten different Central and South American nationalities bring their kids and their picnics or food trucks to the soccer tournament in Queens, New York. Eight distinct Asian countries and cuisines are now represented in what used to be LA's Chinatown.
These new people, whether immigrants from another continent or that other world called suburbia, use the city, drawing from all it has to offer, ignoring the rules of single-use places and buffered uses. Families, seniors, and young people seeking the convenience of urban life are also flooding multifaceted cities -- looking for ways to work, play, learn, invent, and explore these ever-evolving places. Will this energetic mix be zoned out of cities by one-color thinking, or will it be invited to manipulate the mix of uses?
And while urban diversity and urban populations are growing, productive land is shrinking. Resources -- water, energy, and raw materials -- will soon be stretched to breaking. As of 2010, the World Bank documented shortages of resources for 40% of the population.
We must act now to make cities ready for the future. There is much to learn from global populations that thrive on the multifaceted and literally multilayered intensity of a great city neighborhood. Can we make our cities a joy, an adventure, and a great land-use sandwich of diversity and serendipity?
Here's one intriguing idea: Let's feed cities from the roof![A video by LMN architects, about their green roof for the Vancouver Convention Center] The Roof as Fifth Façade: The Farm
What if we imagined every city district, every urban structure, and every building site as a potential farm? A place to build a rich soil, served by a light-touch infrastructure of renewal and regeneration?
Food devotees across the U.S. are making roofs productive.
In some cities, it's already happening: As the icing on the cake of a truly mixed-use building, food devotees across the United States are making roofs productive. A roof garden of herbs or beehives is often where it starts for restaurants, food stores, and even government buildings. But that's only the beginning. Helen Cameron, of Uncommon Ground in Chicago, harvested 659 pounds of organic produce last year for her restaurant off her 640-square-foot rooftop farm. Brooklyn Grange, a commercial, one-acre rooftop farm in Queens, New York, takes on the challenge of a much larger urban roof and invites participation by young and old members of the community. Another commercial venture, BrightFarms, designs and builds greenhouses on roofs, including for supermarkets that then sell that produce.The Ingredients
With a diverse range of uses that contribute to the urban fabric -- whether nourishing community life with engaging uses at the ground level or healthy living with produce on the roof -- we can begin to imagine the ingredients of the land-use sandwich.
Bread: For this open-faced land-use sandwich, we begin with the bread. At the base, buildings are rooted in the city's systems but demand only what they cannot generate themselves. Water will be critical, both fresh and more often grey water for reuse. New structures will anticipate varied loads and services, while many others can be retrofit.
Protein: As the meat of the sandwich, the first floor is ready for uses that bring daily activity, serve the neighborhood, and take productive advantage of the visibility and easy access at that level -- businesses providing jobs, goods, and social spaces in retail and food service, along with work spaces for artisans and small-scale production of products and services. The second and third floors are always laid out and oriented for flexibility -- more space for the business on the ground level, or a separate education, cultural, or service space.
Crunch: The remaining floors may continue this flexibility, or transition to more determined plans for housing, businesses, live/work spaces -- or something entirely new, like a place for packaging and selling roof crops.
Greens: We plant the roof, going beyond the impressive benefits of the now familiar green roof to an intensively productive space linked and leased and in demand for single users (such as a local-food restaurant), cooperative residents, local businesses managing multiple roof spaces, or the grocery store downstairs.
In the "local food" economy, we still must demonstrate the economic feasibility of investing in the roof structure, services, and maintenance. Our current zoning and form-based codes may need some tweaking to protect the rights to this mix of uses and its agricultural fifth façade. Retrofit buildings may need some structural reinforcement to support soil, water, and rooftop farmers, but new buildings can anticipate this need in each neighborhood.New City Delights: A Balanced Meal
We can all attest to the beauty of a well-composed sandwich. The flavors are distinct and yet more enjoyable when consumed together.
The same can well be true for a great street, a new urban district, or an entire city. Perhaps it is here that we can hold on to the concept of authenticity that distinguishes great cities one from another, builds civic identity, characterizes memorable neighborhoods, attracts visitors and brings them back for more. We can imagine plugging in a variety of uses to ready building systems, and allowing downtowns, waterfronts, and old industrial districts evolve as they celebrate the idiosyncrasies and innovations of new populations.
It is time to break out the whole pantry of land-use ingredients and begin stacking them in some unexpected ways -- ways that nourish the economic, social, and environmental diversity of cities.
Written by Karen Alschuler, Perkins+Will's global leader for urban design and a principal in the San Francisco office. Her projects focus on a new generation of urban waterfronts and transforming large urban districts.
[Top image by Matej Novak]