Small California cities update ADU ordinances in 2026 to align with state housing law

Small cities and counties across California are continuing to revise their accessory dwelling unit (ADU) ordinances in 2025 and 2026 to comply with evolving state housing mandates, reflecting how local governments are interpreting and implementing state law differently.

Communities including San Anselmo, Contra Costa County, Pleasant Hill and Petaluma have adopted or amended local ADU regulations within the past year to align with state requirements, according to municipal ordinances, planning department updates and guidance from the California Department of Housing and Community Development (HCD).

Under California law, local ADU ordinances must comply with state statutes and the HCD has authority to review local ordinances and notify jurisdictions of inconsistencies (HCD ADU Handbook, 2025).

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State ADU Law Continues to Expand

California began significantly reforming ADU regulations in 2016, but major expansions occurred between 2019 and 2023. Amendments effective Jan. 1, 2023 further limited local discretion on setbacks, height restrictions and owner-occupancy rules (HCD, 2025).

According to HCD, local governments must:

• Approve qualifying ADUs ministerially
• Act on applications within 60 days
• Allow at least one ADU and one junior ADU on qualifying single-family lots
• Limit setbacks to four feet in many cases

If a local ordinance conflicts with state law, the state statute prevails.

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San Anselmo Amends Code in 2025

The Town of San Anselmo adopted updates to its ADU ordinance in mid-2025 to remain consistent with state requirements, according to town council records and municipal code revisions.

Planning staff presented amendments addressing height limits, objective design standards and parking provisions to ensure alignment with 2023 state amendments. The revised ordinance incorporated the four-foot setback rule and clarified ministerial approval timelines. According to town meeting minutes, officials cited guidance from HCD to ensure compliance.

Local leaders acknowledged during public hearings that while neighborhood concerns about parking and wildfire access were raised, state law limits the extent to which those concerns can restrict ADU approvals (San Anselmo Town Council records, 2025).

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Contra Costa County Revises Standards in Early 2026

Contra Costa County adopted revisions to its countywide ADU ordinance in early 2026, according to planning commission materials and updated zoning code language. The changes clarified height allowances for detached ADUs, aligned setback rules with state law and updated review procedures to meet the 60-day approval requirement mandated by HCD.

County planning staff noted during public review sessions that prior language needed technical corrections to fully match post-2023 state amendments. According to HCD’s compliance review framework, jurisdictions that fail to update local codes are still required to apply state standards directly (HCD, 2025).

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Pleasant Hill and Petaluma Update Ordinances in 2026

In 2026, additional small jurisdictions adjusted their ADU policies.

The City of Pleasant Hill approved zoning amendments in early 2026 to align with state height and setback requirements, according to city council agenda documents. The update removed provisions that could have conflicted with state law and clarified objective design standards.

Similarly, the City of Petaluma revised portions of its ADU ordinance in 2026 to ensure consistency with state mandates regarding parking exemptions and lot coverage limits, according to planning department reports.

Municipal staff in both cities cited HCD guidance and state housing accountability provisions when recommending revisions.

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Differences in Local Interpretation

Although state law establishes minimum ADU allowances, local governments retain authority to adopt objective standards related to design, height and lot coverage — as long as those standards do not “unduly constrain” development (HCD Handbook, 2025).

According to the League of California Cities, smaller jurisdictions often face unique challenges implementing state housing reforms due to staffing capacity, infrastructure limitations and environmental constraints.

In practice, this has led to variations:

• Some cities apply stricter aesthetic design standards.
• Others adopt streamlined frameworks to encourage ADU production.
• Counties may impose different fire-safety overlays depending on local geography.

Housing policy analysts note that while compliance is mandatory, interpretation of objective standards can vary across jurisdictions.

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Increased State Oversight

HCD has expanded its oversight authority in recent years, particularly following broader housing accountability reforms enacted between 2019 and 2023.

According to HCD’s compliance review process, the department may notify jurisdictions if their ADU ordinances conflict with state law and require corrective action. If corrections are not made, the state standards apply by default.

This oversight has prompted many small cities to proactively revise their ordinances in 2025 and 2026 rather than risk noncompliance.

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Statewide Housing Strategy

State officials continue to view ADUs as a key strategy to address California’s housing shortage. According to HCD housing production reports, ADUs have represented a growing share of new residential permits statewide since reforms began.

While implementation varies by jurisdiction, the trend in 2026 reflects a broader pattern: small cities are updating local zoning codes to match state mandates while attempting to preserve local planning priorities.

As cities like San Anselmo, Pleasant Hill and Petaluma adjust their ordinances, the ongoing revisions illustrate how state housing law continues to reshape local land-use authority across California.

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Quick Tip: Because California’s ADU statutes override conflicting local rules, homeowners should review both their city’s most recently adopted ordinance and the California Department of Housing and Community Development’s 2025 ADU Handbook before beginning a project. In many cases, state standards — including reduced setbacks and streamlined approval timelines — may provide greater flexibility than older local codes suggest.

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Xavier Rodriguez is the CEO of ADU Geeks, San Diego’s leading ADU consulting and project management firm. In 2024, the company was ranked No. 1 on the San Diego Business Journal’s Fastest Growing Private Companies list in the Small Business category, achieving 594.3% revenue growth.