To: Board of Supervisors
Department or Agency Name(s): Permit Sonoma
Staff Name and Phone Number: Scott Orr 707-565-1925, Isabella Wotring 707-565-2618
Vote Requirement: Majority
Supervisorial District(s): Countywide
Title:
Title
1:45 P.M. Inland Countywide Z (Accessory Dwelling Unit Exclusion) Combining District Removal
End
Recommended Action:
Recommended action
Hold a public hearing and adopt an Ordinance:
• Finding the action statutorily exempt from the California Environmental Quality Act (CEQA) pursuant to Public Resources Code Section 21080.17, and alternatively not subject to CEQA pursuant to State CEQA Guidelines Section 15061(b)(3) (the common sense exemption); and
• Amending Sonoma County Code Chapter 26 (Zoning Code) as shown in Exhibit A; and
• Updating the Official Zoning Database as shown in Exhibit B to remove the Z (Accessory Dwelling Unit Exclusion) Combining District countywide from parcels outside of the Coastal Zone, for compliance with State law and to support General Plan goals, policies, and programs.
end
Executive Summary:
The proposed elimination of the Z (Accessory Dwelling Unit Exclusion) Combining District from Sonoma County Code (SCC) Chapter 26 and subsequent removal of the zoning designation from 3,997 parcels, located outside of the Coastal Zone, is necessary for compliance with State law. On January 9, 2025, the County received a letter from the California Department of Housing and Community Development (HCD), which evaluated compliance of the County’s Zoning Code with State law pertaining to accessory dwelling units (ADUs) and junior accessory dwelling units (JADUs). HCD’s letter identified the Z Combining District (SCC Chapter 26, Article 76), among other code sections, as a source of noncompliance with State ADU Law. HCD directed the County to either:
A. Provide detailed analysis and findings of fact relating to the four conditions claimed by Zoning Code Article 76 to support prohibition of ADU development wherever the Z Combining District is applied; or
B. Amend the Code to remove the Z Combining District entirely, relying on case-by-case application of standards to determine whether an ADU may be supported.
On September 3, 2026, the Planning Commission voted unanimously to recommend adoption of an ordinance removing the Z Combining District (Article 76) and updates to the Official Zoning Database as shown in Exhibit B to the proposed Ordinance. This recommendation is consistent with Option B as outlined by HCD.
Discussion:
Background on State ADU Law
State housing law continues to evolve to remove regulatory barriers to housing development. Recent changes to State law now require local jurisdictions to allow a certain quantity of ADUs in any zone where other forms of residential development (i.e. single-family dwellings, multifamily dwellings, and mixed-use developments) are permitted uses, and describe an optional allowance that jurisdictions may choose to allow in addition to the mandated minimum allowance.
Background on Z Combining District
The Z (Accessory Dwelling Unit Exclusion) Combining District was established to prohibit specifically ADUs, but not other forms of residential development, in areas where water supply, wastewater disposal, fire hazard, and traffic hazards are of concern. The Z Combining District has historically been applied for a variety of reasons, not always for the purposes described in Article 76, and often without documented reasoning or evidence to support its application.
Project Description and HCD Direction
Removal of the Z Combining District is necessary to ensure compliance with State ADU Law. Violations of State ADU Law may result in notification by the State Department of Housing and Community Development (HCD) to the State Attorney General.
On January 9, 2025, the County received a letter from the California Department of Housing and Community Development (HCD), which evaluated compliance of the County’s Zoning Code with State law pertaining to ADUs and junior accessory dwelling units (JADUs). HCD’s letter identified the Z Combining District (SCC Chapter 26, Article 76), among other code sections, as a source of noncompliance with State ADU Law. This letter, included in Attachment 4, directed the County to either:
A. Provide detailed analysis and findings of fact relating to the four conditions claimed by Zoning Code Article 76 to support prohibition of ADU development wherever the Z Combining District is applied; or
B. Amend the Code to remove the Z Combining District entirely, relying on case-by-case application of standards to determine whether an ADU may be supported.
On February 7, 2025, Permit Sonoma responded to the ordinance review letter, committing to address HCD’s requests and asking for further guidance (see Attachment 5).
HCD has provided guidance that while jurisdictions may adopt detailed analysis and findings of fact to prohibit the optional local allowance of ADUs, they cannot make findings to preclude the State’s minimum allowance of ADUs in areas where other forms of residential development are allowed. Since the County’s ADU regulations only permit the State-mandated quantity of ADUs and do not provide the optional allowance of ADUs, the County may not apply the Z Combining District as currently applied.
In the absence of the Z Combining District, existing County regulations and standards for development outside of the Zoning Code will be sufficient to evaluate ADUs on a case-by-case basis for adequacy of water supply, wastewater disposal, and fire safety, in a manner that is compliant with State ADU Law. For complete discussion of these issues, please see the Planning Commission staff report included in Attachment 3.
The proposed Ordinance would do the following:
• Amend Sonoma County Code Chapter 26 (Zoning Code) to remove the Z (Accessory Dwelling Unit Exclusion) Combining District for compliance with State law, as shown in Exhibit A; and
• Update to the Official Zoning Database to remove the Z Combining District countywide from parcels outside of the Coastal Zone, as listed in Exhibit B and shown on the map in Attachment 7.
Prior Board Action
On December 9, 2025, the Board of Supervisors adopted Ordinance No. 6544 which addressed the majority of HCD’s comments regarding compliance of the County’s ADU ordinance with State ADU Law except the comment regarding the Z Combining District. The amendments proposed now seek to address this remaining comment by following HCD’s direction to eliminate the Z Combining District.
General Plan Consistency
Proposed amendments to County Code are consistent and compatible with the overall goals and intent of the General Plan. Proposed amendments continue implementation of the purpose of Housing Element Policy Subprogram 15b to maintain compliance with State ADU Law. They are also consistent with Housing Element and Environmental Justice Element policies that encourage the retention and further construction of ADUs and aim to provide a variety of housing opportunities throughout the county for all household income cohorts while avoiding the displacement of existing residents. Proposed amendments are consistent with the Water Resources Element and Safety Element as ADUs will continue to be evaluated for compliance with State and local building and fire code during permit review for standards pertaining to water supply, wastewater disposal, and fire prevention.
Planning Commission Review
On September 3, 2026, the Planning Commission held a public hearing to consider the proposed amendments to the Zoning Code and updates to the Official Zoning Database to remove the Z Combining District countywide from parcels outside of the Coastal Zone. The Commission unanimously voted to recommend adoption of the proposed Ordinance (Resolution No. 26-017, Attachment 2).
Environmental Review
The proposed actions are statutorily exempt from the California Environmental Quality Act (CEQA) under Public Resources Code Section 21080.17 which provides that adoption of an ordinance by a city or county to implement State ADU Law is exempt from CEQA. Proposed actions would implement State ADU Law by eliminating the Z Combining District as an inconsistency between County Code and State ADU Law as directed by HCD. In the alternative, the proposed actions are not subject to CEQA pursuant to CEQA Guidelines Section 15061(b)(3) (the ”common sense” exemption) because CEQA applies only to projects which have the potential for causing a significant effect on the environment. Since purposes of the Z Combining District are accounted for and evaluated on a case-by-case basis under existing County standards and procedures during permit review and/or are considered invalid reasons to preclude ADUs under State ADU Law, and since State-mandated ADUs must be allowed on inland parcels regardless of whether the Z Combining District remains, it can be seen with certainty that removal of the Z Combining District from inland parcels and the proposed amendments to the Zoning Code will have no potential to cause a significant effect on the environment.
Recommendation
Staff recommends that the Board adopt an ordinance (Attachment 1) finding the action statutorily exempt from the California Environmental Quality Act pursuant to Public Resources Code Section 21080.17 and pursuant to State CEQA Guidelines Section 15061(b)(3) (the common sense exemption), amending Sonoma County Code Chapter 26 (Zoning Code) as shown in Exhibit A, and updating the Official Zoning Database as shown in Exhibit B to remove the Z (Accessory Dwelling Unit Exclusion) Combining District countywide from parcels outside of the Coastal Zone, for compliance with State law and to support General Plan goals, policies, and programs.
Strategic Plan:
N/A
Racial Equity:
N/A
Was this item identified as an opportunity to apply the Racial Equity Toolkit?
No
Prior Board Actions:
August 22, 2023: Adoption of the 2023-2031 Housing Element <https://sonoma-county.legistar.com/LegislationDetail.aspx?ID=6318630&GUID=F5D1AA7F-A015-4A1B-BB05-697866F7AE02&Options=&Search=>
December 5, 2023: Adoption of Ordinance No. 6458 <https://sonoma-county.legistar.com/LegislationDetail.aspx?ID=6437914&GUID=857F14EC-AFF9-4419-B098-F8A3691521E0&Options=&Search=> to implement Housing Element Subprogram 15b
December 9, 2025: Adoption of Ordinance No. 6544 <https://sonoma-county.legistar.com/LegislationDetail.aspx?ID=7768004&GUID=D5440DBB-77CD-40AA-B9F8-4E76D4A89599&Options=&Search=> to address the majority of inconsistencies with State ADU Law identified by HCD’s ordinance review letter to the County
Fiscal Summary
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Narrative Explanation of Fiscal Impacts:
N/A
Narrative Explanation of Staffing Impacts (If Required):
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Attachments:
Attachment 1: Draft Ordinance with Exhibit A and Exhibit B
Attachment 2: Planning Commission Resolution No. 26-017, September 3, 2026
Attachment 3: Planning Commission Staff Report, September 3, 2026
Attachment 4: State Department of Housing and Community Development ADU Ordinance Review Letter dated January 9, 2025
Attachment 5: Sonoma County Response to ADU Ordinance Review Letter dated February 7, 2025
Attachment 6: Ordinance No. 6544 for ADUs and JADUs adopted December 9, 2025
Attachment 7: Map of Parcels Proposed for Rezoning
Attachment 8: PowerPoint Presentation
Attachment 9: Legal Notice of Public Hearing with Pre-Adoption Summary and Affidavit
Attachment 10: Public Comment
Related Items “On File” with the Clerk of the Board:
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