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Two-Unit Development and Lot Splits (SB 9)

Community Development Agency
Under SB 9, there are many scenarios that can be utilized to build more housing on a single-family residentially zoned lot.

Marin County, like other parts of the region and State, is experiencing an ongoing housing crisis. Many households are not able to locate available and affordable homes.

Senate Bill 9 (SB 9), the Housing Opportunity and More Efficiency (HOME) Act, is a California State Law that took effect January 1, 2022. The Statewide law changes density limits in single-unit (single family) zones with the goal of increasing housing supply. SB 9 makes it easier to apply for a lot split or two-unit development in a single-unit zone that meets certain criteria. This can help communities add more housing options and allow property owners to create new investment opportunities.

 

SB 9 can be used to:

  • Add new homes to an existing parcel;
  • Divide an existing house into multiple units; and
  • Divide a parcel and add homes.

The law streamlines housing development by waiving discretionary review and public hearings. An eligible project may qualify for a ministerial permitting process without hearing or environmental review under the California Environmental Quality Act (CEQA).

Is my property eligible?

A parcel may be eligible for ministerial review under SB 9, subject to the criteria listed below, if it is within:

  • a single-unit residential zone; and
  • a U.S. Census defined urbanized area. The Census defines an urbanized area as one with a minimum of 2,000 housing units or 5,000 people.

Use the mapping tool below to preliminarily identify if your parcel is potentially eligible for SB 9 in unincorporated Marin.

⇨ Click on the picture below to access the full-size map (opens in a new window).

Interactive mapping tool to help property owners preliminarily identify if their property is eligible for SB 9. 

This map is a preliminary screening tool to help property owners understand a parcel’s potential eligibility as a SB 9 project. It does not reflect site-specific conditions that may affect a lot’s eligibility under Marin County Development Code Sections 22.32.184 (Housing Development) and 22.80.064 (Urban Lot Splits Under Senate Bill 9), or other applicable law. This map does not do any of the following:

  • determine eligibility for an SB 9 project;
  • serve as a substitute for documentation demonstrating that a site is eligible; or
  • identify all requirements that may apply to a SB 9 project.

Learn more about specific criteria and requirements by reading Marin County Development Code Sections 22.32.184 and 22.80.064, We always recommend that you get help from the County’s Planning Department before you apply. 

How do I Apply?

To apply or to learn more about if your property is eligible, contact the County’s Planning Department. Planning Customer Service, 3501 Civic Center Drive, Suite 308. San Rafael, CA 94903. Open Monday through Thursday from 8:00 am until 4:00 pm and Fridays from 8:00 am until noon. Phone No. (415) 473-6269.

 

What Can be Built Under SB 9?

Under SB 9, the conditions of the existing site along with the project proposal can result in different potential scenarios of new units. These are detailed in this SB 9 overview provided by the Association of Bay Area Governments (ABAG) and below.

Unit potentials under SB 9 if the lot -

Is vacant:

  • Existing units: 0
  • Adding units with no lot split: up to 2 units and 1 ADU and/or JADU
  • Adding units with a lot split: up to 4 total units

Contains a single-unit home:

  • Existing units: 1
  • Adding units with no lot split: up to 2 units and 1 ADU and/or JADU
  • Adding units with a lot split: up to 4 total units

Contains a single-unit home and an ADU:

  • Existing units: 1 and 1 ADU/JADU
  • Adding units with no lot split: can add 2 additional units (1 must be a JADU)
  • Adding units with a lot split: up to 4 total units

Contains a single-unit home, an ADU and a JADU:

  • Existing units: 1, 1 ADU and 1 JADU
  • Adding units with no lot split: can add 1 additional unit
  • Adding units with a lot split: up to 4 total units

For project-specific questions, contact the Planning Department. Planning Customer Service, 3501 Civic Center Drive, Suite 308. San Rafael, CA 94903. Open Monday through Thursday from 8:00 am until 4:00 pm and Fridays from 8:00 am until noon. Phone No. (415) 473-6269.

Core Site Criteria

The project may not be eligible if it is located on a site containing any of the following.

  • Historic site or district and sites listed on the State Historic Resources Inventory or carry a local historic designation.
  • Prime farmland or farmland of statewide importance, as defined by the U.S. Department of Agriculture land inventory and monitoring criteria.
  • Wetlands, as defined in the U.S. Fire and Wildlife Service Manual, Part 660 FW 2 (June 21, 1993).
  • Habitat for protected specifies identified as candidate, sensitive or species of special status by state or federal agencies, fully protected specifies, or specifies protected by the Federal Endangered Species Act of 1973, the California Endangered Species Act or the Native Plant Protection Act.
  • Lands under conservation easement.
  • For an urban lot split, both lots do not adjoin a public right-of-way. A developed lot with a residence may be able to join a private street.*
  • Very high fire severity zone, as determined by the Department of Forestry and Fire Protection pursuant to Public Resources Code Section 51178, or within high or very high fire hazard severity zone as indicated on maps adopted by the Department of Forestry and Fire Protection pursuant to Section 4202 of the Public Resources Code.
  • Hazardous waste site listed pursuant to Section 65962.5 or designated by the Department of Toxic Substances Control pursuant to Section 25356 of the Heath and Safety Code.
  • Delineated earthquake fault zone, as determined by the State Geologist in any official maps published by the State Geologist.
  • Special flood hazard area subject to inundation by the 1 percent annual change flood (100-year flood) as determined by the Federal Emergency Management Agency (FEMA) in any official maps published by the FEMA.
  • Regulatory floodway, as determined by FEMA in any official maps published by FEMA.

For a comprehensive understanding of criteria and limitations, contact the Planning Department. Planning Customer Service, 3501 Civic Center Drive, Suite 308. San Rafael, CA 94903. Open Monday through Thursday from 8:00 am until 4:00 pm and Fridays from 8:00 am until noon. Phone No. (415) 473-6269.

*In April 2024, the Board of Supervisors will consider an amendment to Marin County Development Code Sections 22.80.064 (Urban Lot Splits Under Senate Bill 9) to remove this requirement.

Other Requirements

  • Finding of specific, adverse impact: The County may deny an urban lot split if the Building Official makes a written finding that the proposed housing development would have specific, adverse impact to public health and safety of the physical environment and where there is no feasible method to mitigate or avoid. This is defined in paragraph (2) of subdivision (d) of Government Code Section 65589.5.
  • Short-term rental restrictions: Any rental unit on a lot created under this law must be rented for a term longer than 30 days. A deed-restriction will be recorded against the property.
  • Public services and facilities: The lots are required to have easements for the provision of public services and facilities.
  • Parking: Up to one space per unit. However, parking requirements are not imposed if the lot is located:
    • within ½ mile of a high-quality transit corridor or major transit stop
    • within one block of a car share vehicle
  • Residential use: Any lot created is limited to residential use.
  • Owner-occupancy for at least 3 years: Applicants for an urban lot split must sign an affidavit stating that the applicant intends to occupy one of the housing units as their principal residence for a minimum of three years from the date of approval. Community land trusts are exempt from this requirement.

For a comprehensive understanding of criteria and limitations, contact the Planning Department. Planning Customer Service, 3501 Civic Center Drive, Suite 308. San Rafael, CA 94903. Open Monday through Thursday from 8:00 am until 4:00 pm and Fridays from 8:00 am until noon. Phone No. (415) 473-6269.