SB 9 

SB9 and SB10

The information provided below is an initial introduction to SB 9 as adopted by the state and may be subject to change pending direction from the City Council and the adoption of SB 9 compliant local regulations.


Senate Bill 9 (SB 9) 
SB 9 became effective on January 1, 2022 and allows for the ministerial (staff-level) approval of certain housing development projects containing up to two (2) residential units (i.e. duplexes) on single-family zoned parcels.  SB 9 also allows for the staff level approval of certain lot splits in single-family zoned areas and the creation of up to two (2) residential units on each newly created lots.

Interim Guidance

Starting January 1, 2022, homeowners interested in adding a residential unit or conducting a lot split under SB 9 can apply for a staff level permit with the City subject to the criteria below:

Qualifying Criteria 

  1. The property is zoned single-family residential (i.e. R1-A, R1-B, or R1-C).
  2. The project does not require the demolition or alteration any housing unit that has been occupied by a tenant within the last three 3 years.
  3. The project site cannot have been withdrawn from the rent controlled rental market within the past fifteen 15 years (subject to the Ellis Act).
  4. The project does not require the demolition of more than 25% of the existing exterior walls of a structure.
  5. Rental of any unit created under SB 9 must be for a term longer than 30 days (i.e. no short-term rentals).
  6. The property, if located in a very high fire hazard zone, earthquake fault zone, floodplain, floodway, and/or a site with hazardous materials, meets certain conditions specified in state law.

Development Standards
Existing and statutory objective development standards will be enforced, such that:

  1. Objective standards do not preclude the construction of up to two 2 units of at least 800 square-feet each in floor area.
  2. No setbacks are required for existing legal structures or structures constructed in the same location and dimensions of an existing legal structure.  Otherwise, a minimum 4-foot setback from the rear and side property lines may be imposed.
  3. One off-street parking space per unit is required except no off-street parking is required for projects located:
    1. Within a 1/2 mile walking distance of a high-quality transit corridor or a major transit stop. 
    2. Within one block of a car share.
      The Hillsdale, Hayward Park, and San Mateo Caltrain stations are considered major transit stops. El Camino Real is considered a high-quality transit corridor.
  4. Individual units may be attached or detached, provided that the structure(s) meet building code safety requirements and are sufficient to allow separate conveyance.

Lot Splits
Lot splits carried out under SB 9 must meet the same criteria as listed above, in addition to the following:

  1. PARCEL SIZE. Each new parcel must be at least 1,200 square-feet in size (i.e., parcel being split must be at least 2,400 square-feet in size)
    1. Each new parcel may be no smaller than 40% of the original parcel’s size. 
  2. ACCESS. Newly created parcels shall have access to, provide access to, or adjoin the public right-of-way.
  3. USES ALLOWED. Each parcel is limited to residential use.
  4. NONCONFORMITIES. The correction of existing legal nonconformities will not be imposed as a condition of approval for any lot split under SB 9.
  5. SEQUENTIAL LOT SPLITS. Sequential splitting of a parcel established through a prior SB 9 split is prohibited. Nor can there be a lot split if the owner of the parcel being subdivided (or someone working in concert with that owner) has subdivided an adjacent parcel pursuant to this lot split legislation.
  6. ADUs & JADUs. The creation of new accessory dwelling units (ADUs) or Junior ADUs (JADUs) may be restricted on parcels created under the provisions of SB 9.
  7. AFFIDAVIT. Owners must sign an affidavit that they intend to occupy one of the housing units as their principal residence for a minimum of three (3) years from the date of the lot split approval.
  8. MAP EXTENSIONS. A subdivision map may be extended for up to four (4) years with a 24-month extension period.

Application Forms

Duplex Development
Planning Application Form
Property Owner Authorization Form
Planning Application Deposits and Processing Costs Form
Screening Criteria Form – Second Unit (Duplex) Development
Tenant Disclosure Affidavit – Second Unit (Duplex) Development

Urban Lot Split
Planning Application Form
Property Owner Authorization Form
Planning Application Deposits and Processing Costs Form
Plan Set Requirements Checklist
Screening Criteria Form – Urban Lot Split
Owner Occupancy Affidavit – Urban Lot Split
Submittal Requirements Checklist – Urban Lot Split

Adoption of Local SB 9 Regulations 

The City of San Mateo will be initiating an ordinance update for compliance with SB 9 and will be seeking City Council direction and community input on policy issues where the state provides flexibility.  Adoption of a local ordinance by the City Council will include:

  • Step 1 (Early-Mid 2022): City Council Study Sessions
  • Step 2 (Late 2022): Planning Commission Public Hearing to review draft ordinance for recommendation to City Council
  • Step 3 (2022/2023): City Council Public Hearing to review proposed ordinance. 


Outreach will be conducted during the course of the project through email notifications and informational meetings.  To receive email updates, sign up for the Planning eNewsletter.  To be added to an interested parties list, please send an email to Laura Richstone, Associate Planner at


City Council Study Session #1 (Virtual)
Date: Tuesday, February 22, 2022
Time: 5:30 p.m. - 7:00 p.m.
Meeting Materials:  Meeting Materials  and Meeting Video

Community Workshop #1 (Virtual)
Date: Tuesday, May 17, 2022
Time: 6:00 to 7:30 p.m.
Meeting Materials: Presentation and Meeting Video

City Council Study Session #2 (Hybrid)
Date: June 6, 2022
Time: 5:30 p.m. - 7:00 p.m.
Location: City Hall Council Chambers: 330 West 20th Avenue or remote through

Community Workshop #2
Date: TBD
Time: TBD

 City Contact Information

Laura Richstone
Associate Planner
(650) 522-7205