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Conduct a noticed Public Hearing and consider adoption of an ordinance approving Zone Text Amendment No. ZT-26-02 amending Chapter 28 of the Solano County Code to update regulations governing accessory dwelling units and junior accessory dwelling units for consistency with State law; the project is exempt from the California Environmental Quality Act (CEQA) pursuant to Public Resources Code section 21080.17 and CEQA Guidelines section 15061(b)(3)
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Published Notice Required? Yes _X_ No ____
Public Hearing Required? Yes _X_ No ____
RECOMMENDATION:
The Department of Resource Management (Department) recommends that the Board of Supervisors:
1. Read the proposed ordinance by title only and waive further reading by majority vote;
2. Conduct a noticed public hearing and consider Zone Text Amendment No. ZT-26-02; and
3. Adopt the proposed ordinance approving Zone Text Amendment No. ZT-26-02 and amending Chapter 28 of the Solano County Code to update regulations governing accessory dwelling units and junior accessory dwelling units for consistency with State law (Attachment A).
SUMMARY:
The proposed ordinance replaces Section 28.72.10(B)(2) of the Solano County Code governing accessory dwelling units (ADUs) and junior accessory dwelling units (JADUs) in the unincorporated areas of Solano County. The amendments align County regulations with current State law, establish updated ministerial review procedures and development standards, clarify the types and locations of ADUs and JADUs, and implement Housing Element Program E.3.
FISCAL IMPACT:
The costs associated with preparing and processing this agenda item are nominal and included in the Department’s FY2026/27 Working Budget.
DISCUSSION:
On February 6, 2024, the Board of Supervisors adopted the 2023-2031 Housing Element. The proposed amendments implement Housing Element Program E.3 by updating the County’s zoning regulations for consistency with current State law governing ADUs and JADUs.
Overview
ADUs are independent residential units allowed on properties with an existing or proposed primary dwelling. They provide additional housing opportunities, potential rental income for property owners, and flexible housing options for multigenerational households. They may provide lower-cost housing opportunities, rental income for property owners, and flexible housing options for multigenerational households.
Solano County has identified ADUs as a key strategy for meeting State housing production and affordability requirements. Recent surveys by the Association of Bay Area Governments found that a substantial portion of Bay Area ADUs are occupied by very low-, low-, and moderate-income households. Under the current Regional Housing Needs Allocation approved by the State Department of Housing and Community Development, unincorporated Solano County must maintain adequate zoning capacity to accommodate 315 housing units across varying income levels. In 2025, ADUs represented approximately 35 percent of residential building permits issued by the County, while single-family dwellings represented approximately 45 percent.
Due to the importance of ADUs, State law continues to evolve by limiting local regulations and encouraging additional ADU development. Solano County's existing ADU regulations were last updated in 2020 and are no longer fully consistent with current State law. Since 2020, the California Legislature has enacted multiple bills amending Government Code Section 66310 et seq., imposing new requirements on local jurisdictions. As a result, the County has applied State standards where existing County regulations conflict with State law, creating uncertainty for applicants and staff.
Housing Element Program E.3 requires the County bring its zoning regulations into compliance with current State ADU law. The proposed amendments replace the existing ADU ordinance in Section 28.72.10(B)(2) in its entirety with regulations intended to be consistent with current State law.
Summary of Changes:
Allowed ADU Types and Locations
The ordinance clarifies the types of ADUs permitted on residential and mixed-use parcels, including: (a) detached ADUs; (b) attached ADUs, including conversion of existing partially enclosed spaces; (c) ADUs created within the space of an existing single-family dwelling or accessory structure; and (d) junior accessory dwelling units (JADUs) contained entirely within an existing or proposed single-family dwelling. Attachment D provides examples of common ADU configurations. ADUs are permitted on any legal parcel in a residential or mixed-use zoning district that contains an existing or proposed single-family or multifamily dwelling.
State ADUs
State law requires local agencies to ministerially approve certain ADUs meeting prescribed standards. Consistent with Government Code Section 66323, qualifying “State ADUs” must be approved ministerially through the building permit process. State ADUs are not subject to the additional local development standards (size, setback, parking, and buildable lot coverage) except as specifically required by State law. The amendment updates local regulations to specify the four categories of State ADUs:
• One ADU within the space of a single-family dwelling or existing accessory structure.
• One new detached ADU (up to 800 square feet (sf)) on a lot with a proposed or existing single-family dwelling.
• ADUs within non-livable portions of existing multifamily dwelling structures (up to 25 percent of existing units, or at least one existing unit, whichever is greater).
• Detached ADUs on lots with existing multifamily dwellings (up to eight, not exceeding the number of existing units) or proposed multifamily dwellings (up to two).
Junior Accessory Dwelling Units (JADUs)
The amendment updates JADU standards consistent with Government Code Sections 66323 and 66333. One JADU is permitted per lot with an existing or proposed single-family dwelling. JADUs must:
Be created entirely within the walls of an existing or proposed single-family dwelling;
• Be limited to 500 square feet of interior livable space;
• Include an efficiency kitchen and a separate exterior entrance;
• Include separate sanitation facilities or share sanitation facilities with the primary dwelling; if facilities are shared, provide an interior connection to the primary dwelling; and
• Be subject to a recorded deed restriction addressing rental terms, separate sale, size, and other applicable ordinance requirements.
Development Standards for Local ADUs
ADUs that do not qualify as State ADUs are approved ministerially but are subject to local development standards. In addition to the ADUs required by State law, the proposed ordinance authorizes one local ADU. Attached local ADUs may not exceed 50 percent of the primary dwelling’s livable space or 1,200 square feet. Detached local ADUs are limited to 850 square feet in R-TC zones, or 1,000 square feet for units with more than one bedroom, and 1,500 square feet in R-R zones. The minimum size for an ADU or JADU is 150 square feet. Due to the State law requirement that the County must ministerially approve State ADUs and at least one local ADU, under certain circumstances, a property with a single-family dwelling in a residential zoning district may accommodate up to three ADUs (two State ADUs, one local ADU) and one JADU.
Application Processing and General Standards
The ordinance establishes application processing timelines and general requirements for ADUs and JADUs, including:
• Applications must be deemed complete or incomplete within 15 business days of receipt and approved or denied within 60 days after receipt of a complete application.
• Correction of nonconforming zoning conditions, code violations, or unpermitted structures that do not present a threat to public health and safety and are unrelated to the ADU or JADU construction may not be required as a condition of approval.
• ADUs and JADUs may not be used as short-term rentals and may only be rented for terms permitted under Section 28.01. Owner-occupancy is not required for a property with an ADU. Owner-occupancy is required for a JADU that shares sanitation facilities with the primary dwelling unless the owner is a governmental agency, land trust, or housing organization.
• Impact fees may not be imposed on ADUs with less than 750 square feet of floor area or on JADUs with 500 square feet or less of interior floor area. Impact fees for larger ADUs must be proportionate to the square footage of the primary dwelling.
• ADUs and JADUs shall not be considered new residential uses for density, connection fees, or capacity charge purposes, and shall not be counted under any ordinance, policy, or program limiting residential growth.
• The ordinance identifies the maximum number and combination of local and State ADUs allowed on qualifying single-family and multifamily residential properties.
General Plan Consistency
The proposed ordinance is consistent with the objectives, policies, land uses, and programs of the Solano County General Plan. Specifically, the proposed amendments implement the General Plan’s Housing Element Program E.3, which directs the County to amend its Zoning Regulations as necessary to be consistent with current State ADU law. The ordinance does not modify General Plan land use designations or zoning districts. ADUs and JADUs permitted in accordance with State law are deemed consistent with a property’s applicable General Plan designation and zoning.
Environmental Review
The proposed zone text amendment is exempt from CEQA under Public Resources Code section 21080.17 because it implements State ADU and JADU law. It is also exempt under CEQA Guidelines Section 15061(b)(3), the Common Sense Exemption, because it can be seen with certainty that the amendment would not result in a significant effect on the environment.
Agency Review
Planning Commission
On May 7, 2026, the Planning Commission conducted a noticed public hearing and recommended approval of the ordinance with minor revisions to improve clarity and address one comment from the California Housing Defense Fund.
Solano County Airport Land Use Commission (ALUC)
On July 9, 2026, the ALUC adopted Resolution No. ALUC-26-011 determining that the project is consistent with the Travis Air Force Base, Rio Vista Airport, and Nut Tree Airport Land Use Compatibility Plans.
Public Noticing Requirement
Notice of the public hearing was published in the Fairfield Daily Republic at least 20 days before the hearing, and notice was mailed to all persons who requested notification (Attachment C).
ALTERNATIVES
The Board may choose not to adopt the proposed ordinance or may direct revisions. This alternative is not recommended because the ordinance implements Housing Element Program E.3, updates the County Code for consistency with current State law, and was recommended for approval by the Planning Commission.
OTHER AGENCY INVOLVEMENT:
None.
CAO RECOMMENDATION:
APPROVE DEPARTMENTAL RECOMMENDATION