Puget Sound Regional Council

Inclusionary zoning stipulates that new residential development in certain zones include some proportion or number of affordable housing units, or meet some type of alternative compliance. To offset costs, jurisdictions often increase the development rights (i.e., density) of a proposed project. Adopting this combination of mandatory affordable housing and increased density into the local code a priori an actual development application distinguishes inclusionary zoning from other types of incentive zoning.*


Mandatory inclusion of affordable housing in residential developments is a response to persistently high housing costs and the difficulty of building lower-cost market-rate housing in many areas due to high land prices, as well as to conclusions (based on real-world evidence) that voluntary incentive programs are ineffective at producing significant numbers of affordable housing units (The Housing Partnership, 2007).

Mandatory inclusionary housing requirements have rarely been used in Washington State due to concerns about takings challenges and the appearance of establishing a “tax.” However, recent amendments to the Growth Management Act (RCW 36.70A.040) and other state laws allow jurisdictions to enact or expand affordable housing incentive programs as long as they are tied to an upzone or other regulation changes that increases the area’s development capacity.

Affordable housing must be mentioned explicitly as a public benefit to be rewarded with increased density, reduced parking, reduced fees or taxes or other incentives offered.

See density bonuses for more information about state law, and voluntary inclusionary programs.

* Note: Some refer to the increased density, gained in exchange for affordable housing, as “density bonuses” regardless of whether the exchange was mandatory or voluntary. Without claiming that any of these terms have a single, correct and unambiguous definition, this Housing Tool Kit uses “density bonuses” to describe voluntary programs and “inclusionary zoning” for the mandatory, a priori program described here.

Helpful Links

General Resources

Municipal Research and Services Center of Washington: Affordable Housing Ordinances/Flexible Provisions
Center for Housing Policy, Toolbox: Capitalize on Market Activity
The Housing Partnership: The Ins and the Outs: A Policy Guide to Inclusionary and Bonus Housing Programs in Washington [pdf]

National Examples

California Coalition for Rural Housing: California Inclusionary Housing Database
National Housing Conference: California’s Inclusionary Zoning Experience
Boulder, CO: Inclusionary zoning regulations [pdf]
Massachusetts: Smart Growth/Smart Energy Toolkit, Inclusionary zoning

Central Puget Sound Region

Kenmore: Inclusionary zoning in downtown zones, see section 18.77
Kirkland: Kirkland Zoning Code: Affordable housing incentives – multifamily, see Chapter 112
Redmond: Inclusionary zoning in some neighborhoods, see section 20D.30.10-020

Tool Profile

Focus Areas

Project Types

Affordability Level

Housing Goal


*Tool considered very effective for producing units at less than 80% AMI.


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