The Basics of Zoning
What is Zoning?
Zoning is the process by which local governments regulate the use and development of land. For a given parcel of land, zoning laws dictate what types and sizes of buildings can be built, how those buildings interact with surrounding buildings or parcels of land, and, perhaps most importantly, the purpose for which the parcel or buildings occupying that parcel can be used.
Why Does Zoning Exist?
The first formal zoning codes in the US were created in the early 1900s. They were primarily focused on controlling or managing urban growth, which accelerated rapidly following the second industrial revolution in the late 1800s. For example, residents worried about industrial factories that might be built in residential and shopping districts while new framing systems meant buildings could be tall enough to completely block sunlight for neighboring buildings. In response to these and other issues, in 1916, New York created what is widely known as the first comprehensive zoning code. This early zoning code primarily regulated building height and setbacks, with a focus on protecting New Yorkers’ access to sunlight and ventilation at street level, but also designated specific districts for particular types of uses. Municipalities across the country quickly followed suit.
As more communities across the country moved to enforce their own zoning codes, challenges emerged, especially with respect to housing. Ultimately, the Supreme Court would rule in two landmark cases that would forever shape the future of zoning and housing in the US. First, in the 1917 Buchanan v. Warley case, the Court prohibited race-based zoning on the basis that such ordinances would limit the rights of property owners to sell to whomever they desired. Nearly a decade later, the Euclid v. Ambler decision upheld municipalities’ rights to regulate or restrict the construction of multifamily housing. Both cases underscore the complex relationship between law, urban planning, and housing economics. While the Buchanan v. Warley case challenged overt racial discrimination, the ruling left room for systemic inequities that continue to manifest in the form of zoning that Euclid v. Ambler explicitly validated - the development of dense, affordable multifamily housing.
How Zoning Works
How to Find Your Property’s Zoning
Since zoning codes are unique to the municipalities that create and maintain them, the language used to distinguish one land use from another may vary. The next section outlines some of the most common zoning classifications, which dictate how a parcel of land may be used. However, to find the classifications and zoning information for a specific piece of real estate, the best place to start is your local municipality’s website, which will typically provide zoning maps and other resources to allow users to view the regulations that pertain to a piece of property. In smaller jurisdictions where online resources aren’t available, contact your local planning or zoning department directly.
What are the Zoning Classifications?
Residential - In residential zones, land is used for housing. Residential zones usually allow either multifamily or single-family dwellings. However, the latter is significantly more common than the former. In Connecticut, for example, 2023 Ivory Prize Winner National Zoning Atlas recently found that over 91 percent of the state’s land is zoned to allow single-family housing by right, compared to just two percent for multifamily.
Commercial - Commercial zoning areas are designated for business activities. Since there is a wide variety of activities that fit this description, municipalities often distinguish between uses like retail, office, hotel, and entertainment.
Industrial - Industrial zoning is used primarily for manufacturing, warehousing, and freight transportation. Industrial land uses can have a significant impact on the environment, and many municipalities separate these uses into the categories of Light Industrial and Heavy Industrial based on the severity of this impact.
Agricultural - Agricultural zones protect and regulate the use of land for farming activities. Some codes may include regulations on the types of crops grown, the number and type of animals allowed per acre, and the use of buildings on the property.
Mixed-Use - Land zoned as mixed-use allows for the integration of residential, commercial, and sometimes light industrial uses within the same district. This approach aims to increase community vibrancy and efficiency. A common form of development in mixed-use zones is multifamily apartment buildings with retail stores or other commercial spaces at the ground floor.
Special Purpose - For land uses that don’t fit cleanly into one of the other categories, municipalities may use special purpose zoning. These zones may be designed to preserve historic buildings, promote cultural uses such as museums or theaters, or prevent development on land used for recreation.
Zoning Regulations
At the highest level, zoning codes determine what land uses are allowable for a given parcel. However, one of the biggest ways zoning impacts the built world is by dictating how these uses manifest in the built world. Here’s an overview of some of the most common forms of zoning regulation and their implications:
Density Regulations - These rules control the number of units or the amount of floor space that can be developed on a certain amount of land. They often include limitations on the number of buildings per acre or the ratio of floor area to the size of the lot (commonly referred to as Floor Area Ratio or FAR). Density regulations can have major implications on the amount of housing supply in a given area. Many urban areas in the US have far more jobs than they do units of housing. This drives up housing costs for those who can afford to live near their work and increases transportation costs for those who cannot. In spite of this inefficiency, many property owners combat density based on the belief that increased density will change the character of their neighborhoods.
Height Restrictions - Height limits are often imposed to control the skyline, sunlight access, and neighborhood character. The creation of the earliest zoning codes, in New York, were triggered in large part by the construction of the Equitable Building in 1915, which was reported to cast a 7-acre shadow over downtown Manhattan. While height limits do not explicitly limit density, they have a similar effect on limiting housing supply.
Setback Requirements - Setbacks determine how far buildings must be from the property line. They affect privacy and light access for neighboring properties but also have implications for public space and the character of the streetscape for pedestrians.
Aesthetic Controls - These regulations govern the appearance of buildings. For developers, zoning ordinances often guide what materials, colors, and architectural styles are allowable for new buildings. While these aesthetic considerations can help ensure that the cultural and historical heritage of a neighborhood is preserved, they can also add to development costs and timelines.
Parking Requirements - Many municipalities include minimum requirements for the provision of off-street parking in their zoning codes. In residential uses, requirements for parking are often tethered to the number of units of housing on a given parcel. The need to provide large surface parking lots means that developers must purchase much more land than they plan to actually build on, and surface lots can also negatively impact the aesthetics of a neighborhood and reduce the availability of green space. While developers can opt to build parking structures or provide underground parking, these options can dramatically increase the cost of a project. For these reasons, a movement against parking requirements has emerged in the past decade, with a growing number of municipalities rolling back or eliminating these regulations from their zoning codes.
Environmental Regulations - Zoning codes are often used for the important job of protecting natural systems and resources such as watersheds, tree canopy, and floodplains. Municipalities may incorporate such considerations throughout all land uses but can also limit or altogether prohibit development in certain areas in the name of preserving natural land. As with all of the regulation forms listed here, environmentally minded zoning laws can manifest in increased housing costs by way of limiting land availability for the development of housing supply.
Zoning Solutions
New developments in how zoning code is written, implemented, and enforced are reshaping how cities meet contemporary urban challenges. Here are some of the solutions that cities have begun adopting more widely of late:
Form-Based Codes - Form-based codes focus on the physical form of the built environment rather than the separation of uses, which is typical in traditional zoning. This approach emphasizes the design of public spaces, the appearance of buildings, and the relationship between them. It promotes walkable, aesthetically pleasing neighborhoods with a mix of uses, such as housing, retail, and offices.
Transit-Oriented Development (TOD) - TOD is a type of community development that includes a mixture of housing, office, retail, and/or other amenities integrated into a walkable neighborhood and located within a half-mile of public transportation facilities, such as light rail stations or bus stops. This approach aims to reduce dependency on automobiles and promote public transit use.
Inclusionary Zoning - Inclusionary zoning requires or incentivizes developers to provide a proportion of units in new residential developments at affordable prices for lower-income households. This can be mandatory or voluntary, often in exchange for development rights or bonuses.
Adaptive Reuse Ordinances - These ordinances facilitate the conversion of existing buildings—often historic or underutilized structures—into different uses, such as turning old warehouses into apartments or offices. This not only preserves the architectural heritage but also revitalizes neighborhoods.
Digital Tools - Advancements in GIS and other digital mapping technologies have enabled more dynamic and transparent zoning practices. Digital zoning maps and apps allow both planners and the public to visualize potential development impacts, understand zoning restrictions, and participate more actively in planning processes. For developers, tech-enabled tools allow for quick identification of parcels optimal for development, determinations of what can be built on a given lot, and feasibility studies, all of which support more efficient delivery of new housing supply.
Innovations in Zoning
Ivory Innovations appreciates the critical role that zoning plays in housing affordability. Utilizing the solutions outlined above along with other novel mechanisms, the following organizations from Ivory Innovations’ portfolio are making zoning codes more density-friendly, easier to navigate for developers and policymakers, and more inclusive of affordable housing:
Buncombe County - North Carolina’s Buncombe County is working to assist private and non profit developers in providing housing low to moderate income families. Their efforts creating more affordable housing through unique zoning and density bonuses for developments that include affordable or workforce housing units.
City of Cambridge: Affordable Housing Overlay Program - Cambridge, MA's 100% Affordable Housing Overlay significantly promotes more dense affordable housing development by non-profit developers, who often get priced by
market-rate developers and are mired by cumbersome zoning and project approvals.
City of Minneapolis: HB 2001 - The City of Minneapolis is “upzoning” nearly the entire city, which will allow more units to be built in areas that previously only contained single-family homes, while promoting transit-oriented development and inclusionary zoning. The so-called Minneapolis 2040 Plan is unprecedent and transformative, providing a model for other cities to broadly address affordability challenges associated with single-family zoning.
DeepBlocks - Deepblocks is utilizing technology to reshape development and entitlement decisions through a real-time analysis of financial and market data, in combination with local building regulations.
National Zoning Atlas - The National Zoning Atlas is a collaborative of researchers digitizing, demystifying, & democratizing about 30,000 U.S. zoning codes through a first-of-its-kind user-friendly online resource. The Atlas will illuminate zoning laws and unlock research that will reveal how zoning impacts housing availability and affordability, transportation systems, the environment, economic opportunity, educational opportunity, and our food supply.
Oregon: HB 2001 - The State of Oregon expanded affordable housing options through the passage of HB 2001 in 2019. The law requires all Oregon cities with populations over 10,000 to allow duplexes on all residential lots on which a single-family home is allowed. Cities over 25,000 and Portland Metro jurisdictions must also allow triplexes, fourplexes, townhomes, and cottage clusters in areas where single family homes are allowed.
Symbium - Symbium is a computational law platform that mechanizes the rules and regulations of planning codes to help homeowners, design professionals, and planners quickly determine if an ADU is allowed on a property, what the development standards are, and processes needed to build these units.
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