To: Board of Supervisors
Department or Agency Name(s): Permit Sonoma
Staff Name and Phone Number: Scott Orr and Isabella Wotring, (707) 565-1900
Vote Requirement: Majority
Supervisorial District(s): Countywide
Title:
Title
1:45 P.M. Accessory Dwelling Unit (ADU) Ordinance Update
End
Recommended Action:
Recommended action
Hold a public hearing and adopt an Ordinance finding the action statutorily exempt from the California Environmental Quality Act pursuant to Public Resources Code Section 21080.17 and amending Sonoma County Code Chapter 26 (Zoning Code) pertaining to accessory dwelling units (ADUs) and junior accessory dwelling units (JADUs) for compliance with State law and to support General Plan goals, policies, and programs.
end
Executive Summary:
The primary objective of the proposed Ordinance is to align the County’s inland Zoning Code, Sonoma County Code Chapter 26, with State law surrounding accessory dwelling units (ADUs) and junior accessory dwelling units (JADUs) and to implement the County’s Housing Element goals and policies for encouraging the construction and retention of these units.
ADUs are dwelling units permitted as accessory to a primary single-family or multifamily dwelling, complete with their own independent living facilities. A JADU is a special type of ADU no greater than 500 square feet that is converted from existing space within a single-family dwelling and may share sanitary facilities with the primary dwelling. In recent years, the State legislature has frequently enacted changes to State ADU Law (Chapter 13 of Division 1 of Title 7 of the Government Code pertaining to ADUs and JADUs) with the intent of decreasing arbitrary, excessive, or burdensome requirements that unreasonably restrict the ability of homeowners to create this valuable form of housing. State ADU Law sets parameters for the provisions that local agencies may and may not apply, with significant changes to State legislation taking effect at the start of 2025.
The proposed Ordinance would make updates to the County Zoning Code necessary to maintain compliance with State ADU Law and respond to an Ordinance Review Letter from the State Department of Housing and Community Development (HCD) that the County received in January 2025 without rolling back existing allowances. In addition to the allowances mandated by State law, Permit Sonoma recommends updates to provide the same quantity of ADUs required by State law, but with flexibility in configuration such that ADUs may be attached, detached, or converted from existing space. Other minor elective updates proposed are recommended in support of General Plan goals and policies that encourage ADU production, seek to provide housing for all household income cohorts in diverse neighborhoods, and encourage programs which reduce impervious surfaces associated with development.
On October 2, 2025, the Planning Commission voted unanimously to recommend adoption of the proposed Ordinance.
Permit Sonoma recommends the Board of Supervisors adopt the proposed Ordinance, finding the project exempt from CEQA and amending Chapter 26 of the County Code (Zoning Code) pertaining to ADUs and JADUs to align with State law and support General Plan goals, policies, and programs.
Discussion:
Project Description
The proposed Ordinance will update Zoning Code provisions for accessory dwelling units (ADUs) and junior accessory dwelling units (JADUs) and reorganize the existing structure and location of relevant code sections for better clarity.
Housing Element Subprogram 15b directed staff to update the Zoning Code to maintain compliance with State law for accessory dwelling units. This was accomplished in 2023 with the adoption of Ordinance No. 6458. However, State ADU Law has evolved since 2023, and additional updates are now required to maintain compliance. General Plan Policies HE-5g and HE-6e further direct the County to continue to encourage the construction and retention of small rental units such as accessory dwelling units, and to provide housing opportunities throughout the county for all household income cohorts while avoiding displacement of existing residents.
The proposed Ordinance includes updates to standards and permitting provisions for compliance with State ADU Law while allowing flexibility in the types of ADUs a lot may contain and retaining certain existing local standards. This is achieved by allowing the minimum quantity of ADUs that must be permitted under Government Code Section 66323, while applying more permissive standards than those outlined in the State law, as permitted under Government Code Section 66325. This approach allows the inclusion of ADU configurations that the County already permits while fulfilling the minimum allowable quantity mandated under Section 66323. The proposed amendments would allow for ADUs and JADUs in the quantities summarized in Table 1.
Table 1. Allowable ADU & JADU Combinations Under Proposed Ordinance
|
With Primary Dwelling: |
Single-Family Dwelling (SFD) |
Multifamily Dwelling (MFD) |
|
|
Existing or Proposed |
Existing |
Proposed |
|
Conventionally permitted ADUs & JADUs - any combination of the following shall be permitted by proposed standards compliant with Government Code Sections 66323 and 66333. Existing unpermitted units permitted under Section 66332 may count against these allowances. |
|
JADU |
One (1) JADU |
- |
- |
|
Detached, new construction ADU |
Two (2) ADUs of any type |
Eight (8) ADUs of either type but not exceeding the number of existing primary units on the lot |
Two (2) ADUs |
|
ADU attached to an existing primary dwelling or accessory structure |
|
|
|
|
ADU converted from an existing accessory structure |
|
|
|
|
ADU converted from existing space within a primary dwelling structure |
|
At least one (1) ADU or up to 25% of existing primary units on the lot -must be converted from non-livable space |
- |
|
ADU attached to a proposed single-family dwelling |
|
- |
- |
|
Unpermitted ADUs and JADUs eligible for permitting under Government Code Section 66332 may count against allowances for conventionally permitted ADUs and JADUs but shall not affect or be limited by those already constructed. |
|
ADUs and JADUs constructed prior to 2020, and not in substandard condition |
As many as eligible |
As many as eligible |
As many as eligible |
The proposed Ordinance includes the following key elements:
1. Additions to, updates to, and reorganization of definitions.
2. Relocation of code sections and reorganization of code section structure.
3. Removal of redundant requirements and rewording of references to building and fire code requirements.
4. Adjustments to standards to accommodate a variety of ADU types in compliance with Government Code Section 66323, including:
a. Elimination of minimum parking requirements.
b. Reduction of front setback and lot coverage standard applicability.
c. Increase to the maximum height for detached and attached ADUs.
d. Elimination of special design standards for ADUs used to meet affordable housing requirements under Article 89.
5. Clarification of permitting processes and addition of permitting provisions for unpermitted ADUs and JADUs constructed prior to January 1, 2020.
6. Clarification of allowances for ADUs and JADUs where nonconforming zoning conditions exist.
7. Inclusion of uncovered spaces in replacement parking provisions for ADUs.
8. Removal of obsolete Net Zero groundwater use requirements for ADUs.
9. Removal of the preclusion of ADUs by agricultural employee housing units.
10. Clarifications regarding the applicability of the Riparian Corridor (RC) and other combining districts.
State ADU Law
For purposes of this report, “State ADU Law” includes State provisions for ADUs and JADUs included in Title 7, Chapter 13 of the California Government Code (Sections 66310-66342). Substantial updates to State ADU Law went into effect January 1, 2025, with the passing of Senate Bill 1211 (2024) and Assembly Bill 2533 (2024). These bills prohibit local agencies from imposing any development standards on specific ADUs and JADUs that are not authorized under Government Code Section 66323; raise the quantity of detached ADUs allowed on multifamily lots from two to up to eight; and require jurisdictions to offer a specific pathway for the legalization of certain unpermitted ADUs and JADUs while enhancing amnesty protections.
Government Code Section 66323 establishes a minimum quantity of ADUs and JADUs a jurisdiction must allow per lot, subject to certain minimum allowances and maximum restrictions. These units are typically referred to as “State-mandated units” or “statewide exempt units”. This includes a certain quantity of accessory units of various configurations depending on the type and quantity of primary units on the lot. Government Code Section 66314 provides for an optional allowance for ADUs not described in Government Code Section 66323. Government Code Section 66325 provides that jurisdictions may apply standards that are less restrictive than those established by State law.
Under Government Code Section 66332, local jurisdictions must allow legalization of unpermitted ADUs and JADUs which were created prior to January 1, 2020, and are not in substandard condition pursuant to California Health and Safety Code Section 17920.3. No other standards may be applied to these units as a condition of legalization.
State Department of Housing and Community Development (HCD) Communication
Ensuring compliance with State ADU Law is critical to maintaining the County’s Prohousing designation and the certified status of the adopted Housing Element. On January 9, 2025, Permit Sonoma received a letter from the State Department of Housing and Community Development (HCD) regarding the County’s ADU ordinance (Zoning Code Section 26-88-060). The letter identified various contents of the ordinance which appeared outdated or out of compliance with recently updated State ADU Law and directed the County to amend its ADU ordinance or to make findings under Government Code Section 66326(b)(2)(B) explaining why the County’s ordinance is compliant with State ADU Law. This letter is included in Attachment 3. 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). Since then, Permit Sonoma staff has continued engagement with HCD representatives to obtain guidance and clarification pertaining to the restrictions and allowances that may be applied under State ADU Law. The proposed amendments address HCD’s comments and other identified inconsistencies with State ADU Law.
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 15bto maintain compliance with State ADU Law and support the purpose of Subprogram 25dto reduce penalties for existing unpermitted dwellings and to encourage programs to bring them up to code. Additionally, proposed amendments clarify and simplify standards and permitting processes for ADUs while providing flexibility in the configurations of ADUs allowed. These updates are consistent with Housing Element policies that encourage the retention and further construction of ADUs and aim to provide housing opportunities throughout the county for all household income cohorts while avoiding the displacement of existing residents. Proposed amendments are also consistent with Water Resources Element policies that encourage programs to reduce impervious surfaces and increase groundwater recharge as they include simplified height standards that better allow for multistory ADUs subject to the same floor area limitations, allowing for less impervious surface per unit of living space. Further, proposed amendments are consistent with Open Space and Resource Conservation Element policies that encourage the protection of streamside conservation areas as amendments preserve applicability of Riparian Corridor standards.
Planning Commission Review
On October 2, 2025, the Planning Commission held a public hearing to consider proposed amendments to Zoning Code provisions for ADUs and JADUs. The Commission unanimously voted to recommend adoption of the proposed Ordinance (Resolution No. 25-11, Attachment 2). The Planning Commission additionally recommended the following topics to be considered by the Board of Supervisors either with adoption of the Ordinance or with direction to staff on future efforts: application of building envelopes to ADUs; opportunities to confirm water service provider capacity during ADU permit processing; code amendments to limit the use of a primary residential unit as a vacation rental when located on a lot with ADU(s); and opportunities to assess or verify the existence of permitted and unpermitted dwellings on site at the time of new building permit processing including for ADUs.
Staff do not recommend any modifications to the proposed Ordinance subsequent to Planning Commission discussion. The Planning Commission’s comments are either already addressed through current practice or best addressed through direction to staff for future efforts. Building envelopes are and will continue to be applied to ADUs to the extent authorized under State ADU Law. Water service and/or availability is and will continue to be evaluated during the building permit review process for new ADUs. Regulations on primary dwelling occupancy are outside of the scope and objectives of the proposed Ordinance, which focuses on accessory units. Evaluation of the existence of unpermitted structures already occurs through the building permit process and Code enforcement efforts.
Post-Planning Commission Revisions
After the Planning Commission made its recommendation to the Board on adoption of the proposed Ordinance, Assembly Bill 1154 was signed and is set to go into effect at the start of 2026. This bill amends State law pertaining to JADUs to prohibit local jurisdictions from setting owner occupancy requirements on JADUs that have sanitation facilities separate from their associated primary single-family dwelling. Proposed code amendments have been updated to reflect this change.
Environmental Review
Adoption of the proposed Ordinance is statutorily exempt pursuant to Public Resources Code Section 21080.17 which provides that the adoption of an ordinance by a city or county to implement State provisions for ADUs and JADUs is exempt from CEQA.
Recommendation
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 amending Sonoma County Code Chapter 26 (Zoning Code) pertaining to accessory dwelling units (ADUs) and junior accessory dwelling units (JADUs) 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
December 5, 2023: Adoption of Ordinance No. 6458 to implement Housing Element Subprogram 15b
Fiscal Summary
N/A
Narrative Explanation of Fiscal Impacts:
N/A
Narrative Explanation of Staffing Impacts (If Required):
N/A
Attachments:
Attachment 1: Draft Ordinance with Exhibit A
Attachment 2: Planning Commission Resolution No. 25-11
Attachment 3: Planning Commission Staff Report, October 2, 2025
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: PowerPoint Presentation
Attachment 7: Legal Notice of Public Hearing with Pre-Adoption Summary and Affidavit
Related Items “On File” with the Clerk of the Board:
N/A