Senate Bill 9 (SB 9) Guidance

SB9 and SB10


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.

Project Update

  • On Monday September 19, 2022 the City Council voted 4-1 to approve the staff’s recommended draft ordinance
  • A second reading of the ordinance will occur on:
    Date: Monday, October 3, 2022
    Time: 7:00 p.m.
    Meeting Information:

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 The project site cannot have been withdrawn from the rent controlled rental market within the past fifteen 15 years (subject to the Ellis Act).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 2 units of at least 800 square-feet (sq. ft.) each in floor area.
  2. Setbacks.
    1. Minimum 4-foot rear and side yard setbacks; or
    2. No setbacks are required for existing legal structures or structures constructed in the same location and dimensions of an existing legal structure.
  3. Parking.
    1. One off-street parking space per unit is required; or  
    2. No off-street parking is required for projects located:
      1. Within a ½  mile walking distance of a high-quality transit corridor or a major transit stop or;
      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. Unit Type.
    1. Units may be attached or detached, provided that the structure(s) meet building code safety requirements and are sufficient to allow separate conveyance.
  5. Uses.
    1. Establishment of short-term rentals are prohibited.

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

  1. Parcel Size.
    • Minimum 1,200 sq. ft. parcel size (i.e., parcel being split must be at least 2,400 sq. ft. in size); and
    • 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.
    • Each parcel is limited to residential use.
  4. Nonconformities.
    • Correction of existing legal nonconformities will not be imposed as a condition of approval for any urban lot split.
  5. Sequential Lot Splits.
    • Sequential splitting of a parcel established through a prior SB 9 urban lot split is prohibited.
  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.

Application Forms

Duplex Development

Urban Lot Split

Fee Schedule 

Planning fees can be found on page 4.1 of the City’s comprehensive fee schedule.

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 (Complete)
  • Step 2 (Mid-Late 2022): Planning Commission Public Hearing to review draft ordinance for recommendation to City Council (Complete)
  • Step 3 (Late 2022): City Council Public Hearing to review proposed ordinance. (In progress)


Draft Ordinance Overview 

Draft 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

Upcoming Meetings

City Council Public Hearing (Hybrid)
Date: Monday, October 3, 2022 
Time: 7:00 p.m.
Location: City Hall Chambers, 330 W. 20th Avenue, San Mateo, CA

Past Meetings

City Council Hearing

City Council Public Hearing (Hybrid)
Date: Monday September 19, 2022
Time: 7:00 p.m.
Location: City Hall Chambers, 330 W. 20th Avenue, San Mateo, CA
Meeting Materials: Meeting Materials and Meeting Video

Planning Commission Hearing

Planning Commission Public Hearing (Hybrid)
Date: Tuesday August 23, 2022
Time: 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

Community Workshop #2 (Virtual)
Date: Monday, August 8, 2022
Time: 6:00 to 7:30 p.m.
Location: Remote
Meeting Materials: Presentation and Meeting Video 

City Council Study Sessions

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

City Council Study Session #2 (Hybrid)
Date: Monday, June 6, 2022
Time: 5:30 p.m. - 7:00 p.m.
Meeting Materials:  Meeting Materials and Meeting Video

 City Contact Information

Laura Richstone
Associate Planner
(650) 522-7205