Sonoma County, CA Zoning Overlays & Bonuses: Density Bonus Law (2026)

Section 26-89-050(D) of the Sonoma County Code creates the County supplemental density bonus program, one of the density bonus routes in Article 89 of the Zoning Regulations. A residential project of five (5) or more base units is eligible for a bonus of up to fifty percent (50%) above the maximum density allowed by the General Plan and the zone district. The bonus is earned by providing affordable units out of the base unit count, and the code lists eight alternative thresholds: 10 percent of base units for extremely low-income households; 20 percent for very low-income households; 30 percent for low-income senior households; 30 percent for low-income households with 10 percent of those units built as fully accessible units for low-income disabled households; 30 percent for low-income households with 10 percent of those units built as rental units with three (3) or more bedrooms for low-income large families of five (5) or more persons; 40 percent for low-income households; a State-program-qualifying project for very-low or low-income households that also has 33 percent of total units powered by on-site renewable energy meeting at least 70 percent of projected electrical demand; or 30 percent low-income with 100 percent of total units meeting universal design basics, including stepless entry, a single-floor living area with 32-inch doorways, and environmental controls at accessible heights.

The program works inside a larger framework. Under Subsection 26-89-050(A), a project must meet or exceed the affordability thresholds, only one density bonus program can apply to each project, and the bonus cannot attach to General Plan and Zoning Database amendments. It is approved only in conjunction with a development permit: a tentative map, parcel map, Conditional Use Permit, or Design Review. Under Subsection 26-89-050(B), the applicant files with the Department either before or concurrent with the discretionary application. The filing must include a Housing Proposal giving the number, type, size, tenure, bedroom count and affordability level of every unit, name the program and the incentive requested, and supply anything else the Director needs for a complete evaluation. The project approval itself must identify the bonus, the incentives granted, and any waiver or modification of standards.

Section 26-89-060 adds incentives on top of the density. Every project with on-site affordable units gets fast-tracking of permits, concurrent processing, and preference in priority development areas, plus at least one additional incentive such as dropping covered parking, a 20 percent reduction in open space, or a 20 percent reduction in minimum parcel size or width. Subsection 26-89-050 was last amended by Ord. No. 6545 on December 9, 2025.