What Is Mandatory Inclusionary Zoning?

As communities struggle with rising housing costs, local governments are considering a variety of policies intended to produce more affordable homes. One increasingly common approach is mandatory inclusionary zoning.

Mandatory inclusionary zoning (MIZ) is a policy requiring new residential developments to make a designated percentage of their homes affordable to households earning below a specified income level. The requirement generally applies to multifamily developments, although the exact rules vary by jurisdiction.

For example, a city might require that 10% of the apartments in a new development be affordable to households earning no more than 80% of the area median income. The city may also determine how long those homes must remain affordable, establish rent or sale-price limits, and set minimum project sizes to which the requirement applies.

How Does Mandatory Inclusionary Zoning Work?

Under an MIZ program, the below-market cost of the affordable homes is generally absorbed by the overall development. To help offset that cost, a jurisdiction may offer incentives such as:

• Additional building height or density

• Reduced parking requirements

• Lower permit or impact fees

• Tax exemptions

• Faster permit review

• Greater flexibility in development standards

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Some programs also allow developers to pay a fee instead of constructing affordable homes within the project. That revenue is then used to support affordable housing elsewhere in the community.

These incentives matter because an affordable-housing requirement does not eliminate the cost of constructing, financing, and operating the required homes. It changes how those costs are covered.

What Are the Potential Benefits?

Supporters of mandatory inclusionary zoning argue that it can create affordable homes in neighborhoods where publicly subsidized housing may otherwise be difficult to build. It can also promote mixed-income communities and ensure that some of the housing created during periods of growth remains accessible to lower- and moderate-income households.

Unlike programs that depend entirely on public funding, MIZ can produce affordable homes alongside private development. When appropriately designed and paired with meaningful incentives, it can be one component of a broader housing strategy.

What Are the Potential Drawbacks?

The principal concern is that an MIZ requirement can make new housing financially infeasible if its cost exceeds the value of the incentives being offered.

Housing developments must generate enough revenue to pay for land, construction, financing, permits, utilities, taxes, and ongoing operations. Requiring some homes to rent or sell below market value reduces the revenue available to cover those costs.

If a project can no longer secure financing or provide a reasonable return, it may be delayed, reduced in size, or not built at all. This can result in fewer market-rate and affordable homes being produced.

The burden may also fall unevenly. Landowners may receive less for developable property, builders may face narrower financial margins, and market-rate residents may pay more to help offset the below-market homes. Smaller projects and locally owned builders may have less ability to absorb these costs than larger developments.

Policy Design Matters

Mandatory inclusionary zoning is not simply a choice between supporting or opposing affordable housing. The real question is whether a particular program will produce more affordable homes without discouraging the broader housing construction needed to address the shortage.

Before adopting an MIZ requirement, a jurisdiction should conduct a detailed financial feasibility analysis. The analysis should examine local rents, construction costs, land values, interest rates, parking requirements, development standards, and the value of any incentives being offered.

Important policy questions include:

• What percentage of homes must be affordable?

• What income levels will the program serve?

• How long must the homes remain affordable?

• What types and sizes of projects will be covered?

• Are density or height bonuses realistically usable?

• Will parking, design, or development standards prevent builders from using those bonuses?

• Are fees or alternative compliance options available?

• Will the requirements adjust when market conditions change?

A density bonus has value only when a developer can realistically build and finance the additional homes. Allowing more theoretical density does little good if height limits, parking mandates, setbacks, infrastructure constraints, or weak market demand prevent that capacity from being used.

A Balanced Approach to Housing Affordability

Mandatory inclusionary zoning can produce affordable homes, but it cannot replace the need to increase the overall housing supply. Communities should also examine zoning capacity, permitting delays, development fees, infrastructure limitations, parking requirements, and other factors that raise the cost of construction.

An effective housing strategy should combine targeted affordability programs with policies that make it easier to build homes at a range of prices and types.

The goal should not simply be to adopt the strongest-looking requirement. It should be to create a program that works under real-world market conditions and results in more housing actually being built.