2024-RZ-1
Background:
Senate Bill 9 (SB 9) took effect on January 1, 2022 and the provisions of SB 9 currently apply statewide, including within the City of Brisbane. SB 9 allows homeowners in single-family zoning districts (R-1 and R-BA districts), to either add an additional unit on their lot (two-unit development) or subdivide their lot into 2 lots (urban lot split), subject to certain restrictions further outlined below. SB 9 developments do not require discretionary review by the planning commission or city council. Rather, the City is obligated to administratively approve SB 9 projects if they comply with the provisions of SB 9.
- Two-unit Developments: Property owners in the R-1 and R-BA districts may establish two-unit developments (duplexes) on their properties. Eligibility criteria includes considerations for tenant-occupied housing as well as whether the property adjoins a public street and has access to all utility infrastructure required by the Municipal Code.
- Urban Lot Splits: Property owners in the R-1 district and R-BA district may split one property they own, one time, into two developable lots without discretionary review (i.e., reviewed by City staff, not the Planning Commission). There are many eligibility criteria that apply and not all lots will be eligible for an urban lot split. Properties in the R-BA District specifically may be ineligible depending on environmental/habitat and infrastructure constraints.
Additional information relating to Two Unit Developments and Urban Lot Splits is available on the City's website.
The City Council is considering adoption of a zoning ordinance, 2024-RZ-1, to reflect requirements established in SB 9. Below are sample scenarios and frequently asked questions to explain Zoning Ordinance 2024-RZ-1 and its applicability within Brisbane.
How is SB 9 Relevant to Brisbane?
SB 9 applies to single family zoning districts, which are the R-1 and R-BA zoning districts.
It does not apply to multifamily or mixed use zoning districts. The R-1 and R-BA districts are shown in the image below. You may view our interactive Zoning Map to view the City's single family zoning districts and check the zoning designation of any parcel.
What development is currently allowed in the R-1 zone and how does that compare to what SB 9 allows?
The minimum lot size standard in the R-1 distirct is 5,000 sq ft. However, a number of lots are recognized as legal lots that are smaller in size, down to as small as approximately 2,500 sq ft in the R-1 district, based on older lot size standards. The R-1 zoning district allows for one single family dwelling unit, one attached junior accessory dwelling unit (JADU) and one accessory dwelling unit (ADU) on a lot, irrespective of size, assuming the applicable development standards are met. However, there are limitations on the number of ADUs and/or JADUs that are allowed in conjunction with a two unit development.
Taking this into consideration, the maximum number of units (including ADUs) permitted with an SB 9 two unit development is 4 units, where 3 units are permitted under existing zoning regulations.
Another option under SB 9 is an “urban lot split” which allows an existing lot to be split into a maximum of 2 lots. The minimum resulting lot size is 1,200 sq ft, meaning that R-1 zoned lots less than 2,400 square feet in size are not eligible for an urban lot split. A lot that is split pursuant to SB 9 cannot be further subdivided. In any case, the number of units permitted within the original lot boundaries cannot exceed 4. This is not 4 units per lot, but rather 4 units total within the boundaries of the original lot.
(Jump to R-BA examples or Brisbane Case Studies or additional sample concepts.)
The image above conceptually shows allowable configurations allowed under the R-1 Residential Zoning District (~5,000 SF lot), Brisbane's ADU Ordinance, and SB 9. Blue represents a single family home (SFD), yellow an ADU, red a JUDU, and purple is a primary unit (PU) allowed under a two-unit development, with or without an urban lot split.
From left to right:
- SFD - allowed by district regulations;
- SFD, attached JADU, and detached ADU - allowed without SB 9;
- SFD, JADU, ADU, and second detached PU without a lot split; and
- SFD, JADU, ADU, and second detached PU with a lot split. (The red and black dashed-line represents the new boundary line approved under an urban lot split.)
Below is a perspective of the same examples (Starting top left and going clockwise: 1) SFD; 2) SFD with ADU & JADU; 3) SFD with ADU & JADU and second detach PU with a lot split; 4) SFD with ADU & JADU and second detach PU without a lot split.
What development is currently allowed in the R-BA zone and how does that compare to what SB 9 allows?
The minimum lot size in the R-BA zoning district is 20,000 sq ft., although there are a number of recognized legal lots in the R-BA zone that are less than 20,000 square feet. Same as in the R-1 zone, the R-BA district allows for one single family dwelling unit, one attached JADU and one ADU on a lot, irrespective of size, assuming the applicable development standards are met. As described above in R-1 zone, the maximum number of units (including ADUs) permitted with an SB 9 two unit development is 4 units, where 3 units are permitted under existing zoning regulations. Another option under SB 9 is an “urban lot split” which allows an existing lot to be split into a maximum of 2 lots. A lot that is split pursuant to SB 9 cannot be further subdivided.
As noted previously, there are a number of criteria that need to be met for a property to be eligible for an SB 9 project. Several of these criteria are particularly relevant to the R-BA zoning district. One eligibility criteria for SB 9 development is that the lot may NOT have endangered species habitat. The R-BA district as a whole is within the San Bruno Mountain Habitat Conservation Plan area and a number of the properties, especially in the upper reaches of the district, may contain habitat for endangered butterfly species. Any properties containing endangered species habitat would be ineligible for an SB 9 project. Another criteria is that an SB-9 project site must have infrastructure access for safety and utilities. Many of the lots in the R-BA do not currently have road access or utilities and would therefore be ineligible for an SB 9 project until such time such improvements are in place.
The image below shows conceptual site plans of allowable configurations allowed under the R-BA Residential Zoning District (~20,000 SF lot), Brisbane's ADU Ordinance, and SB 9. Blue represents a single family home (SFD), yellow an ADU, red a JUDU, and purple is a primary unit (PU) allowed under a two-unit development, with or without an urban lot split.
From left to right:
- SFD with a detached garage attached JADU, and detached ADU - allowed by district regulations and without SB 9;
- SFD with a detached garage, JADU, ADU, and second detached PU without a lot split; and
- SFD with a detached garage, JADU, ADU, and second detached PU with a lot split. (The red and black dashed-line represents where the new boundary line would be under an approved under an urban lot split.)
(Jump to R-BA examples or Brisbane Case Studies or additional sample concepts.)
If SB 9 already applies to Brisbane why does the City need to adopt an ordinance? What happens if the City chooses not to adopt an ordinance?
The City is not legally required to adopt an ordinance. Since SB 9 took effect in 2022, property owners in Brisbane have had the right to apply for SB 9 developments and the City is obligated to process and approve them if they comply with the development standards set forth in SB 9. These provisions will remain in effect whether or not the City adopts an ordinance.
However, SB 9 allows local jurisdictions to establish and enforce objective development standards for SB 9 developments, provided those standards do not preclude development that would otherwise be allowed. The proposed draft ordinance includes several objective standards intended to reduce the neighborhood impacts of SB 9 developments related to 1) parking and 2) building heights within setbacks and on ridgeline lots, and public transparency as further described below. If the City chooses not to adopt the ordinance the City will not be able to impose these standards.
Proposed Development Standards
SB 9 provides that a jurisdiction may not require more than a 4 foot building setback from the side or rear lot lines for SB 9 projects. Comparing this to the current R-1 district standards, the minimum side setbacks range from 3 to 5 feet, depending on the lot width, and the rear setback requirement is 10 feet. In the R-BA district, the minimum rear setback is also 10 feet and the side setbacks range from 5 to 15 feet, depending on the lot width.
In order to reduce the impacts of state-mandated setbacks that are less than those established by the City, the draft ordinance proposes a reduced building height limit of 25 feet for that portion of a structure that is located between the zoning district’s standard setback requirement and the state established 4-foot setback. The current height limit in the R-1 district is 28 to 30 feet depending on the slope. Additionally, the 25 foot height limit would apply to ridgeline lots within the R-BA district. The current height limit for buildings in the R-BA district is 35 feet.
Per SB 9 provisions, the City may not require more than one parking space for each primary dwelling unit. The draft ordinance proposes the parking requirement may only be met by off-street uncovered parking or carport. While garage spaces may be provided at the owner’s option, they would not count towards the minimum requirement. This proposed standard stemmed from a concern over the common practice of use of garages for storage purposes other than parking. It has also been proposed that shared driveways should be permitted. This would be to allow for fewer driveway curb-cuts, to help minimize impacts to existing street parking.
While SB 9 requires projects to be processed administratively, the ordinance establishes a requirement for adjacent property owners be provided notice that an SB 9 project has been approved on a lot.
Below illustrates the proposed height limit for two unit developments, as it relates to the rear setback area in the R-1 District. Single family homes (blue) are subject to the district maximum of 36 feet (as proposed under 2024-RZ-2) and may be as close as 10 feet to the rear property line. Primary units (purple) permitted under SB 9, which the State allows a reduced 4-foot rear setback, would be limited to 25 feet high in the rear setback area that is 4-10 feet from the rear property line. These units may extend to the district maximum (36 feet) when outside the rear (and side) setback area(s). Also shown, for reference, are ADUs (yellow), which are similarly permitted to be within 4-feet of the rear setback by the State and can be limited to 18 feet tall in certain circumstances, and a typical, 8-foot tall fence in brown.
Sample Scenarios of Two Unit Developments and Urban Lot Splits:
SB 9 allows for two-unit developments and urban lot splits in the R-1 Residential District and R-BA Brisbane Acres Residential District. No more than two primary units may be built on a single lot, whether before or after a lot split, and no more than 4 units (including ADUs and JADUs) may be built across the original lot area. Consistent with SB 9, the draft ordinance provides tables showing the possible scenarios. A few of the many possibilities are illustrated below, based on a 5,000 sq ft lot in the R-1 district.
Base Case, without SB 9:
Single family dwelling (blue).
Existing Zoning , without SB 9:
Single family dwelling (blue), with attached JADU (red) and ADU (yellow).
Two unit development on a single lot:
Single family dwelling (blue), with attached JADU (red) and ADU (yellow), and second detached primary dwelling (purple).
Urban lot Split:
Single family dwelling (blue), with attached JADU (red) and ADU (yellow) on one lot. Single family dwelling unit (purple) on the second lot.
Two Unit Development – Duplex:
Without a lot split an option, pursuant to SB 9, is to develop the site with a duplex, plus two ADUs.
Urban Lot Split – 50:50 Split with Development Type D on both resultant lots:
With an urban lot split, pursuant to SB 9, an option is to develop each resultant lot with a duplex.
Urban Lot Split – 40:60 Split with Development Types B & D:
With an urban lot split, pursuant to SB 9, an option is to develop one resultant lot with a SFD and an ADU and the second resultant lot with a duplex.
Brisbane Case Studies:
Example #1
The owner of a 7,500 SF lot would like to add another dwelling unit. The site currently is developed with a single-family home, attached ADU, and detached garage. The owner proposed to convert the garage to a primary unit and go for a 60:40 lot split.
This could be allowed, utilizing a shared driveway for the existing home and new primary unit, by first obtaining a ministerial parcel map and then a building permit to convert the garage to a dwelling unit.
The owner could also have considered converting the existing attached ADU to a JADU and the detached garage to an ADU; this is also permissable under the City's Zoning Ordinance.
Example #2
The new owner of a home without off-street parking on a 5,800 SF parcel learns the parcel is comprised of two legal underlying lots of record. Since the existing single family home is located on one of the underlying lots and the other is vacant, they'd like to subdivide and build a home on the vacant parcel. However, a survey revealed the home is located only one-foot away from the existing boundary line. The owner proposed to split the lot along the existing boundary line and, some time in the future, build single family home on the resultant vacant lot.
This could be allowed with a lot line adjustment and building permit. The City would require a lot line adjustment to move the boundary at least 4 feet from the existing home and that the property owner add one off-street parking space on the resultant lot with the existing single family. A building permit is needed to construct the carport and must be finaled prior to recordation of the lot line adjustment. When ready, the owner would need a building permit to construct a home on the resultant vacant lot and both parcels would forever be subject to the provisions of SB 9.
Example #3
The owner of a 5,100 SF lot and single family home wants to build two additional units for their extended family. They could build an ADU and JADU but they are not interested in the some of the regulation associated with JADUs. The property is comprised of two irregular yet legal underlying lots of record. The owner proposes to merge the lots and build a second primary unit and ADU.
This could be allowed with a lot merger and building permit. A lot merger is required to establish one legal lot prior to issuance of a building permit for the dwelling units.
More Images:
Key: Single family dwelling (blue), JADU (red), ADU (yellow), and second detached primary dwelling (PU) (purple), duplex (tan). Street perspective of the above below.
Various perspectives of development possibilities grouped together below.
Key: Single family dwelling (blue), JADU (red), ADU (yellow), and second detached primary dwelling (PU) (purple), duplex (tan)
In 2021 the Governor signed SB 9, which became effective for jurisdictions state-wide in January 2022 and the City is currently processing applications pursuant to SB 9.
Through adoption of a local ordinance the City may include objective development standards, as long as those standards wouldn’t preclude development that would otherwise be compliant with the provisions of SB 9. Objective standards are including in the draft ordinance for 1) parking and 2) building heights within setbacks and on ridgeline lots, as further described below. A local ordinance would provide for clarity in the City’s implementation of SB 9 provisions. The draft ordinance would also commit the City to providing an informational notice to the owners of neighboring properties upon approval of a development project under SB 9.
“Two unit developments” generally refers to the development of two primary dwelling units on a an existing lot, or on a lot created through an urban lot split.
An "urban lot split" is a ministerial split of one single family residential lot into two lots pursuant to the provisions of SB 9. Each resultant lot may have a two unit development or a combination of primary dwelling units and JADUs or ADUs. In any case, the maximum development that may occur over the original lot area is 4 dwelling units. That’s one more than may otherwise be permitted.
An overlay district does not alter the underlying district standards. The overlay district (R-TUO Residential Two Unit zoning district) standards would only apply to those properties that apply for a permit pursuant to the provisions of SB 9 and are approved for development consistent with SB 9.
SB 9 only applies to single family zoning districts, which in Brisbane are the R-1 and R-BA zoning districts. These districts are shown in yellow on the zoning map excerpt (see also our Interactive Zoning Map):
The current lot size standard in the R-1 zone is 5,000 sq ft, although a number of smaller lots are recognized as legal lots, generally in the range of 2,500 sq ft to 5,000 sq ft based on older lot size standards. The R-1 zoning allows for one single family dwelling unit, one attached junior accessory dwelling unit (JADU) and one accessory dwelling unit (ADU) on a lot, irrespective of size, assuming the applicable development standards are met.
SB 9 allows for one additional dwelling unit on that same lot area, either following an “urban lot split” or as a “two unit development” on the existing lot, subject to a number of qualifying criteria and restrictions. An urban lot split is a ministerial division of one legal lot into two lots and a two unit development allows for two primary dwelling units, such as two single family dwellings or a duplex on a lot. Regardless of whether SB 9 is implemented by an urban lot split or by a two unit development on the existing lot, the total dwelling unit count for the original lot area may not exceed four units, including accessory dwelling units, versus three units under the current zoning for both districts. There are various potential buildout configurations and comparison examples for:
- what may be developed under the R-1 zoning without SB 9;
- a two unit development; and
- an urban lot split.
These are theoretical examples based on a maximum buildout. Additional examples based on a maximum buildout are available at this link.
The lot size standard in the R-BA zone is 20,000 sq ft. The R-BA zoning currently allows for one single family dwelling unit, one attached junior accessory dwelling unit (JADU) and one accessory dwelling unit (ADUs) on a lot. SB 9 allows for one additional dwelling unit on that same lot area, either following an “urban lot split” or as a “two unit development” on the existing lot, subject to a number of qualifying criteria and restrictions.
One such qualifying criteria is that the lot may not have endangered species habitat. The R-BA district as a whole is within the San Bruno Mountain Habitat Conservation Plan area and a number of the properties, especially in the upper reaches of the district are likely to contain habitat for endangered butterfly species and would therefore be excluded. Another is that the lot must have infrastructure access for safety and utilities. Many of the lots do not currently have such access or utilities. Since this cost is borne by the property owner for development, this will likely continue to prove to be cost prohibitive, especially for those properties that are distant from existing infrastructure and on steep terrain.
The endangered species and infrastructure restrictions are applicable to much of the R-BA district, but there are a number of other requirements and restrictions that may apply to either the R-1 and R-BA. Some of these are as follows:
- The lot does not contain wetlands;
- The lot may not be in a very high fire hazard severity zone;
- The lot may not contain habitat for protected species;
- The lot may not be on lands under a conservation easement;
- The lot has not previously been subdivided via urban lot split;
- For urban lot splits, prior to a lot split being recorded, the property owner(s) shall sign an affidavit stating that the owner, or a member or members of the owner’s immediate family, intends to occupy one of the dwelling units as the person’s principal residence for a minimum of three years; and
- Development may not result in demolition of a dwelling unit that has been occupied by a tenant in the last three years and other tenant displacement protections.
The net increase in dwelling units on a given lot is one (1) unit. Currently a lot of record in either the R-BA or the R-1 district maybe developed with a single family dwelling (SFD), an accessory dwelling unit (ADU) and a junior accessory dwelling unit (JADU) without invoking SB 9 provisions. SB 9 provides for one more unit as a primary dwelling unit. That may be as a detached unit (resulting in a two unit dwelling group) or as a duplex. If the lot is split, as an urban lot split under the SB 9, the mix of units between the two resultant lots may range from 1 to 3 units, but the total across both resultant lots may not exceed 4 units.
This is unknown. Since SB 9 took effect in 2022, owners on a total of 4 lots have applied for SB 9 development via two unit development or an urban lot split, although no development permits have yet been approved. For reference, case studies on three of these projects as provided on the City's website. Also, while there are approximately 880 lots in the R-1 district, lot size, topography, existing construction and other constraints could make SB 9 developments impractical or infeasible. Access and habitat constraints would also likely reduce the feasibility of SB-9 development throughout the R-BA zone.
For a two unit development without a lot split, a property owner would need to obtain a building permit, which would include documentation on eligibility.
For an urban lot split, prior to obtaining the building a lot split would be required, via separate planning application.
As part of the above referenced permits, a deed restriction would be recorded on the property, identifying the property as being developed through SB 9 and subjecting it to certain development and use restrictions, as provided in the ordinance.
Whether the development under SB 9 is a two unit development on the existing lot, or the owner chooses to apply for an urban lot split, prior to submitting for a building permit, the applications require ministerial approval by the City, as long as they meet all of the requirements of SB 9.
Additional information related to the process in Brisbane for Urban Lot Splits & Two-Unit Developments is available on the City's website.
No, but they must be close in size. Pursuant to state law, the allowable size ratio between two resultant lots must be in the range of 40:60 to 50:50. For a 5,000 SF lot, that would be resultant lots in the range of 2,000 SF and 3,000 SF, to 2,500 SF and 2,500 SF, respectively.
The underlying district floor area limits would apply. For the R-1 district that floor area ratio is 0.72, or 3,600 sq ft on a 5,000 sq ft lot, except that the City must allow for primary dwelling units of at least 800 sq ft. An owner may voluntarily develop a smaller unit subject to California Building Code requirements. For the R-BA district, the maximum FAR is also 0.72, except that the total floor area may not exceed 5,500 sq ft.
SB 9 provides that a jurisdiction may not require more than a 4 foot building setback from the side or rear lot lines. Comparing this to the current R-1 district standards, the minimum side setbacks range from 3 to 5 feet, depending on the lot width, and the rear setback requirement is 10 feet. In the R-BA district, the minimum rear setback is also 10 feet and the side setbacks range from 5 to 15 feet, depending on the lot width.
Following the Planning Commission’s workshops and public hearing on the draft ordinance, the Commission recommended an objective standard, that the area between the zoning district’s standard setback area and the state’s 4 foot allowance, the building height may not exceed 25 feet. The current standard in the R-1 district is 28 to 30 feet depending on the slope. Additionally, the 25 foot limit would apply to ridgeline lots within the R-BA district. The current height limit for buildings in the R-BA district is 35 feet. (Note, under the draft ordinance 2024-RZ-2 a height limit of 36 feet has been proposed for both the R-1 and R-BA districts.)
Also, per SB 9 provisions, the City may not require more than one parking space for each primary dwelling unit. Following the Planning Commission’s workshops and public hearing on the draft ordinance, the Commission has recommended an objective standard, that the parking requirement may only be met by off-street uncovered parking or by parking covered by a carport. While garage spaces may be provided, as an owner’s option, they would not count towards the minimum requirement. This proposed standard stemmed from a concern over the common practice of use of garages for storage other than parking.
It has also been proposed that shared driveways should be permitted. This would be to allow for fewer driveway curb-cuts, to help minimize impacts to existing street parking.
Note that, where the R-1 or R-BA zoning district standards are not specifically superseded by the standards provided through SB 9, the underlying zoning district standards would apply.
The development provisions for ADUs and JADUs are contained in BMC Chapter 17.43. These provisions would not be changed by the ordinance. That is with the exception that, the use of a property for an ADU or JADU might be superseded by development of a primary dwelling unit through SB 9, but where an ADU or JADU is allowed, the provisions of Chapter 17.43 would still apply.
A recent ruling by a Los Angeles Superior Court judge’s overturning SB 9 applied to five charter cities in Southern California. The City’s Legal Counsel indicated that the decision has no effect on other trial courts or other cities. Also, the cities in question are charter cities, not general law cities, such as Brisbane, and the decision hinged on SB 9 conflicting with the land use authority of those cities under their charters. As such, the decision is not relevant to SB 9 as it applies to the City of Brisbane.
Subject to certain restrictions, SB 9 allows for two-unit developments and urban lot splits in the R-1 Residential District and R-BA Brisbane Acres Residential District. No more than two primary units may be built on a single lot, whether before or after a lot split, and no more than 4 units (including ADUs and JADUs) may be built across the original lot area. Consistent with SB 9, the draft ordinance provides tables showing the possible scenarios. A few of the many possibilities have been illustrated on the City's website, based on a 5,000 sq ft lot in the R-1 district and a 20,000 sq ft lot in the R-BA district.
Click here for sample scenarios of Two Unit Developments and Urban Lot Splits and three Brisbane case studies.
Supporting Documents
Draft Ordinance 2024-RZ-1 (10 MB) 
