Senate Bill 9 (SB 9) Guidance

SB9 and SB10


Senate Bill 9 (SB 9)

Effective 2022, SB 9 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.

The City has adopted a local Two-Unit Development Overlay District Ordinance (Section 27.21 of the San Mateo Municipal Code) to enact the provisions of SB 9.  


General guiding criteria is provided below. Additional and more specific standards can be found the Municipal Code and Ordinance Overview in the Documents section below:

Qualifying Criteria

  1. The property is zoned single-family residential (i.e. R1-A, R1-B, or R1-C). Property specific zoning information can be found here.
  2. The project does not require the demolition or alteration any housing unit that has been occupied by a tenant within the last 3 years.
  3. The project site cannot have been withdrawn from the rent controlled rental market within the past 15 years (subject to the Ellis Act).
  4. Not located in a historic district or included on the State Historic Resources Inventory.
  5. 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

  1. 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.
  2. Height.
    1. Attached Units – 24 ft. to plateline and 32 ft. to peak as measured from existing grade.
    2. Detached Units – 16 ft. to plateline and 24 ft. to peak as measured from existing grade.  
  3. Parking.
    1. One off-street parking space per unit; 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. Demolition Limit.
    1. Projects that propose 50% or more demolition of a structure’s existing exterior walls are subject to an alternative discretionary review process.
  5. Uses.
    1. Establishment of short-term rentals are prohibited.

 Urban Lot Splits – Additional Standards

  1. Parcel Size.
    1. Minimum 1,200 sq. ft. parcel size (i.e., parcel being split must be at least 2,400 sq. ft. in size); and
    2. Each new parcel may be no smaller than 40% of the original parcel’s size
  2. Access.
    1. Newly created parcels shall have access to, provide access to, or adjoin the public right-of-way.
  3. Uses.
    1. Each parcel is limited to residential use.
  4. Sequential Lot Splits.
    1. Sequential splitting of a parcel established through a prior SB 9 urban lot split is prohibited.
  5. Affidavit.   
    1. 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

General Forms

Two Unit (Duplex) Development

Urban Lot Split

Fee Schedule 

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


Past Meetings

City Council Hearing

City Council Public Hearing #2 (Hybrid)
Date: Monday October 3, 2022
Time: 7:00 p.m.
Location: City Hall Chambers, 330 W. 20th Avenue, San Mateo, CA

City Council Public Hearing #1 (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