Mixed-use development combines retail, office, and residential use and is an element of contemporary planning. It provides a good range of housing choices that increase affordability and equity and mitigate environmental problems by reducing motor vehicle use. It also forms part of a strategy for sustainable development and good urban form with the objectives of attaining economic vitality, social equity, and environmental quality.
Mixed-use is a significant form of land development that upends conventional zoning. This Update discusses the obstacles that conventional zoning creates for mixed-use development and how it can be changed to eliminate zoning problems. A wide array of zoning alternatives is available, which adapt existing zoning strategies, but there is limited understanding of how they function and their advantages and disadvantages.
Zoning, as originally conceived, did not allow mixed-use development. Its purpose was to separate land uses that might harm each other into different zoning districts. Zoning ordinances implement this purpose under a model Standard State Zoning Enabling Act, published by the US Department of Commerce in 1926, which most states adopted.
The Standard Act delegates zoning authority to local governments. It authorizes them to divide municipalities into zoning districts to “carry out the purposes of this act” and regulate land use within such districts. The Act does not provide statutory direction for creating zoning districts nor for the types of land uses that can be included. Standard practice is to create separate districts for residential, commercial, and industrial uses, an approach that does not allow mixed-use development, which an early US Supreme Court case upheld. Village of Euclid v. Ambler Realty Co., 272 U.S. 365 (1926). This zoning practice is based on an implicit land-use pyramid with residential use at the top of the pyramid as the most desirable land use, followed by commercial and industrial uses as less desirable.
Noncumulative zoning is another common zoning practice not required by the Standard Act that limits each zoning district to one use and does not allow different uses to mix in the same zoning district. Cumulative zoning is an alternative that allows mixed-use by permitting more than one use in a zoning district. Residential uses, for example, are allowed in a district zoned for commercial uses. Cumulative zoning can allow mixed-use development, but it is a clumsy fix because it does not control the type of mixed-use development that can be built.
The Standard Act also includes a statutory uniformity clause that could prevent the mixing of uses within zoning districts. This clause provides that “[a]ll such regulations shall be uniform for each class or kind of buildings throughout each district,” but it has not proved troublesome. Most courts have adopted a reasonableness exception, which validates mixed-use zoning notwithstanding the uniformity clause when the mix of uses is reasonable.
Mixed-use development raises several zoning issues. One issue is that local governments must consider how the market will respond to a mixed-use zoning ordinance. The ordinance can permit mixed-use development, but it will be built only if the market responds to what the ordinance permits. Gaps and vacancies in a development would occur, for example, if the space zoned for retail use is not completed because market demand is not there. Zoning for mixed-use development should be preceded by a detailed market study so that it can be written to meet market demand.
A zoning ordinance can authorize mixed-use development through “by-right” zoning that permits mixed-use as a matter of right or through zoning that requires the approval of mixed-use development in a discretionary review process. By-right zoning provides opportunities for mixed-use development without going through discretionary review, which provides certainty for developers and avoids the problems that can occur in a discretionary review process, such as higher costs and delays. The difficulty is that by-right zoning can be inflexible and concede too much control over development mix and character to developers.
Design is the catalyst that brings planned mixed-use development to life. Managing design requires design controls that can shape development character. They can be adopted independently or included in the zoning ordinance. Design standards are one alternative. They are mandatory, objective, and quantitative, similar to site development and density requirements in zoning ordinances. Design standards can include fixed rules for design characteristics, such as building form and mass, but may limit design opportunities if they are too inflexible.
Design guidelines are another alternative that can be objective or subjective. Objective design guidelines control mandatory design features, such as building mass and form. They define design clearly but may be inflexible. Subjective design guidelines, such as a walkability requirement, are indeterminate, qualitative, and not measurable. They are administered through the normal development review process or by a board such as an architectural review board that reviews project designs to determine whether they comply with design guidelines. Problems may occur if ambiguous guidelines allow arbitrary decision-making, and the review and approval process may increase costs and cause delays if not properly managed.
The retail space design is an example of what design guidelines should include, as the proper design and configuration of retail space can determine whether a mixed-use development will succeed. Retail space must be compatible with a mix of complementary uses, vibrant and pedestrian-friendly, and experience-driven with active ground floor space. Design guidelines can address these issues with design criteria for site design, walkability, architectural expression, scale, physical form, and building mass.
For example, Castle Pines, Colorado, has design guidelines for mixed-use districts. City of Castle Pines, Colo., Mixed-Use Design Guidelines (2018). They include core design principles such as community character, balance, placemaking, pedestrian activity, and sustainability. They also include additional design details for each of the core design principles. Walkability is an example. It is an essential requirement for mixed-use development, and a design guideline for connectivity requires “providing pedestrian easements along building frontages where appropriate to provide a walkable network between building entries, public spaces, and adjacent buildings or developments.”
Several developers create this type of mixed-use development through separate, unrelated actions. It requires zoning by right that details uses, densities, and other land-use requirements for mixed-use development. Scale is important, and the zoning ordinance can include by-right mixed-use districts organized by size, such as a small neighborhood, a medium community, a regional development, and a major redevelopment mixed-use district. See Bloomington, Indiana, Unified Development Ordinance Ch. 20.04 (2021).
Design controls can be combined with zoning for unplanned mixed-use development. For example, Montgomery County, Pennsylvania, has a model New Town Mixed Use District. Zoning requirements include land use, land-use mix, and dimensional standards. The design concept states it “is designed for places where compact, walkable, livable, and attractive development is appropriate.” The district defines key design elements, which include a wide variety and diverse mix of uses, pedestrian-friendly building design, unobtrusive parking, and appropriately scaled height. Design standards include general layout, building design, parking, and pedestrian design.
Design standards adopted from form-based codes are another possibility. They are a zoning innovation that expands the typical zoning ordinance with by-right design standards that include the relationship between building facades and the public realm, the form and mass of buildings in relation to one another, and the scale and types of streets and blocks. Mixed-use zoning can include design standards from form-based codes that can provide more control over the design of mixed-use developments.
A zoning strategy known as a floating zone can provide more flexibility for unplanned mixed-use zoning. A floating zone is a zoning district included in the text of the zoning ordinance but not mapped until a developer applies for the district and the local government maps it. Letting the zoning district float until it is mapped allows the local government to decide where it wants mixed-use development to be located and to include customized requirements that determine what kind of mixed-use development will be built.
This type of development requires detailed design controls and zoning that define critical project elements. The Dublin, Ohio, Bridge Street District is an example. It is a form-based code that implements the Bridge Street District Area Plan with detailed design guidelines for a densely developed, walkable, mixed-use planned development in a 1000-acre historic center. City of Dublin, Ohio, Code of Ordinances § 153.057–.066.
A planned unit development (PUD), or planned community, is a land-use development for which a local government approves a development plan that controls the development of the PUD. The ordinance specifies what kind of PUDs the local government will approve. It should also define what must be included in the development plan, such as the objectives and character of the development, residential and nonresidential development standards, guidelines for walkability, public space, and architectural design, and a circulation plan.
Planned unit development is a good choice for mixed-use development because the development plan for a PUD can customize land use and design. The approval process, however, can cause uncertainty and delay if improperly managed, and approval criteria can cause arbitrary decision-making if they are too ambiguous. See New Perspectives on Planned Unit Development, 52 Real Prop. Tr. & Est. J. 230 (2017).
Zoning for mixed-use development requires a zoning choice that must be made from a variety of zoning alternatives. There is no standard metric that can identify a successful zoning model. Decisions must be made on how much to control the market, how much to control mixed-use development, and whether zoning should be by-right or require discretionary review.
