Effective January 1, 2025, SB 450 further limits local agencies’ zoning authority
SB 9 Background
Since January 1, 2022, SB 9 has required local agencies to allow any lot in a single-family residential zone to be: (1) split, roughly into halves, with resulting lots as small as 1,200 sf (termed an “urban lot split”); and (2) developed with a second primary dwelling unit. SB 9 required local agencies to approve urban lot splits and second primary dwelling unit projects ministerially (i.e., without discretionary review, conditions, or a hearing). Property owners can use both SB 9 opportunities — meaning that an urban lot split may be followed by the development of two primary dwelling units on each of the new lots, resulting in four total dwellings on what was formerly one single-family residential lot.
SB 9 allowed local agencies to impose objective zoning, subdivision, and design standards on SB 9 projects, subject to some limitations. Many local agencies exercised this authority by adopting ordinances with robust, specific, objective standards for SB 9 projects (e.g., SB 9-specific setback, unit size, floor: area ratio and height limitations).
SB 450: Reduced Local Control; New Restrictions
In September 2024, Governor Newsom signed SB 450, which will take effect on January 1, 2025. This bill will fundamentally alter the status quo by reducing the scope of local authority to regulate SB 9 projects. Most notably, under SB 450 local agencies:
- May no longer impose standards on second primary dwelling unit projects “that do not apply uniformly to development within the underlying zone” … that is, unless the SB 9-specific standards “are more permissive.”
- May only impose standards on urban lot splits that are “related to the design or to improvements of a parcel” (e.g., lot size, access, and grading).
- Must approve or deny a “completed application” for an urban lot split or second primary dwelling unit project within 60 days. (Failure to act results in the application being deemed approved.)
- Must provide detailed comments with any denial of an urban lot split or second primary dwelling unit application.
- May no longer deny an application for an urban lot split or second primary dwelling due to specific adverse, impacts to the “physical environment” (now only adverse impacts on “public health and safety” are a valid basis for denying an SB 9 application).
Next Steps
As of January 1, 2025, local agencies won’t be able to enforce any of their SB 9-specific requirements, unless those requirements are specifically permitted by statute.
However, it is important for local agencies to understand that their underlying single-family residential zoning standards apply to SB 9 second primary dwelling unit projects, and that only parcel-related standards apply to urban lot splits. This could be complicated for some local agencies.
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