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Supervisors Overturn Commission's Protections Against Dangerous 2nd Units In High Fire Zones

On January 26th, the Marin County Board of Supervisors overturned the protections that the Planning Commission had added to the County’s proposed Development Code Amendments regarding Accessory Dwelling Units (ADUs). The safeguards would have helped to thwart further deterioration of inadequate emergency access and evacuation routes in high fire risk areas caused by unsafe state-mandated ADUs.

More specifically, the Planning Commission’s recommendations would have prohibited ministerial, “by right” approval of all categories of Accessory Dwelling Units (ADUs) at properties located on roadways less than 20-feet-wide, which are also located in the Wildlands Urban Interface (WUI) or in a Very High Fire Hazard Severity Zone (VHFHSZ). A homeowner could have still applied for an Accessory Dwelling Unit permit at these locations and sought a variance or waiver of the prohibition, which could have been granted if the local Fire Protection District determined that adequate emergency access and evacuation routes would be provided.

Rather than increasing ADU restrictions as many residents recommended, the Supervisors removed almost all the protections instead. There are a few remaining restrictions for ADUs in Very High Fire Hazard Severity Zones (VHFHSZ) but these will have little effect.

Besides legal concerns, it seems that a predominant reason that the Supervisors pulled the protections, is because they wish to preserve the ability to identify single-family parcels in the Wildlands Urban Interface (WUI), High Fire Hazard Zones, Very High Fire Hazard Severity Zones, and Environmentally Sensitive Areas as sites in the upcoming Housing Element and use Accessory Dwelling Units (in addition to units in multifamily and mixed-use developments) to fulfill the County’s inflated Regional Housing Need Allocation (RHNA).


The County’s Development Code Amendments incorporate the State’s new Accessory Dwelling Unit (ADU) legislation that was enacted in 2019.

There are various advantages to adding an Accessory Dwelling Unit or second unit to a home. For homeowners, the extra unit can provide additional income, support family members such as adult children or aging parents and house on-site caregivers. In addition, the units may provide additional affordable housing, although this is not guaranteed. When local jurisdictions craft careful Accessory Dwelling Unit ordinances, these second units can fit seamlessly into an established community.

However, by requiring "ministerial" review and stripping away local control of land use, local development standards, community engagement, and environmental review related to second units, the State's new ADU laws went too far.

Ministerial” approval streamlines the permit process and eliminates discretionary review, environmental review, and public hearings, thereby stifling public engagement, democracy, high-quality development, and environmental protections.

Most worrisome, is the fact that, if a jurisdiction doesn't take adequate precautions, then the new ADU laws endanger communities in the Wildlands Urban Interface, High Fire Hazard Zones, Very High Fire Hazard Zones, Environmentally Sensitive Areas, and Constrained Areas with unsafe access and evacuation routes. This is because the laws dramatically increase potential housing density and population (potentially more than doubling the population) in these hazardous communities, while reducing or eliminating off-street parking requirements for ADUs, Junior ADUs, and the primary single-family homes. This will lead to streets being overcrowded with parked vehicles.

Dire consequences could result during an emergency when residents are unable to evacuate and fire trucks/paramedics are unable to reach their destinations.

The Marin Community Wildfire Protection Plan reports;

Approximately 60,000 acres—18% of the county’s land area—falls within the Wildland Urban Interface (WUI) where residences (i.e., homes and structures) are intermixed with open space and wildland vegetation. Because of the mix and density of structure and natural fuels combined with limited access and egress routes, fire management becomes more complex in WUI environments. In Marin County specifically, many of the access roads within the WUI are narrow and winding and are often on hillsides with overgrown vegetation, making it even more difficult and costly to reduce fire hazards, fight wildfires, and protect homes and lives in these areas.”

The Wildfire Protection Plan continues;

"Homes and structures located anywhere in and around the WUI are at a higher risk for exposure to wildland fire. Fire can spread rapidly throughout WUI areas through adjacent structures and/or vegetation, or by ember dispersion.”

The Wildfire Protection Plan further states;

"Narrow paved widths and limited on-street parking create access issues. According to the California Fire Code specifications, roadways that are considered hazardous in terms of fire access and protection are those with:

**For more background information about this issue, please click HERE to read my previous article entitled; “Update – Protect Neighborhoods In High Fire Zones From County’s Proposed Second Unit Regulations”.


The discussion of Marin County’s draft Development Code Amendments, including the Accessory Dwelling Unit regulations, occurred directly after Staff’s presentation regarding the County’s Regional Housing Need Allocation (RHNA) (AKA Housing Quota). Marin County’s RHNA has risen from 185 units (for the 2015 to 2023 planning cycle) to 3,510 units (for the 2023 to 2031 cycle), which is 22 times greater.

What is RHNA?

The Regional Housing Need Allocation (RHNA) is the state-mandated process to identify the total number of housing units (by affordability level) that each jurisdiction must accommodate in its Housing Element (AKA housing plan).


Staff reviewed the proposed Development Code Amendments. During their presentation, they described the draft Accessory Dwelling Unit (ADU) regulations that restricted ADUs in fire prone areas, unless the local Fire Protection District deemed conditions to be safe. They also showed maps of the County’s Wildlands Urban Interface (WUI) and Very High Fire Hazard Severity Zones.

Please click HERE to view an interactive map of the Marin County Wildlands Urban Interface (WUI):


County Fire Chief Jason Weber gave a report on the upcoming Marin Wildfire Prevention Authority study. Chief Weber explained that the study will be completed in about a year, or a year and a half, and will provide scientific and objective mapping and data sets that rate roads, vegetation, and other factors based on fire safety, which will allow for informed decision making.


Supervisors Inquire About The State Accessory Dwelling Unit (ADU) Law:

Supervisor Rice and Supervisor Connolly were the first to make comments. They asked Staff and legal counsel if the Accessory Dwelling Unit (ADU) regulations, recommended by the Planning Commission, were consistent with State law. (All the State ADU regulations have been incorporated into California Government Code § 65852.2.)

County’s Planning Manager responded;

“I will defer to Counsel but I will say that Category 1 ADUs (in the County’s Development Code) really is distinct from the other Categories because it’s what’s called the ‘Subdivision (e)’ category in the State law and it does seem as though the State really places that in a category of its own. And it’s much more of a ‘by right’ expectation… There is risk associated with placing restrictions that are not specifically in State law, as the Planning Commission has recommended regarding the roadways in fire prone areas.”

County’s Legal Counsel agreed;

“ ‘Subdivision (e)’ is a special category under State law of ADU. It is a ‘by right’ category with its own set of restrictions which prohibit local authority... You have that authority reserved in Categories 2, 3, and 4 for example to regulate and prohibit ADUs. You don’t have that in Category 1.”

Staff and County Counsel did not inform the Supervisors about the research that Sustainable TamAlmonte had provided Staff and the Planning Commission during the Commission’s hearings. Sustainable TamAlmonte had presented them with a list of 5 other jurisdictions that prohibited all categories of Accessory Dwelling Units (ADUs) in hazardous areas, copies of those jurisdictions' ADU ordinances, and the legal basis for why two of those other jurisdictions' legal counsel determined that they could indeed protect public safety from dangerous ADUs.

Sustainable TamAlmonte’s prior letter to the Planning Commission explained that other jurisdictions’ legal counsels found ambiguities in the language and intent of the State ADU legislation. Therefore, they followed Gov. Code § 65852.2 (a), rather than Gov. Code § 65852.2 (e).

Gov. Code Section 65852.2 (a) states that a local jurisdiction’s ADU ordinance shall designate where ADUs may and may not be permitted, based on the adequacy of water and sewer services and the impact of ADUs on traffic flow and public safety.

Supervisors Consider Protecting Public Safety Versus Satisfying The County’s Regional Housing Needs Allocation (RHNA):

Besides considering legal parameters, the Supervisors weighed which was more important, protecting public safety or identifying enough sites in the County’s upcoming Housing Element to satisfy the County’s Regional Housing Needs Allocation.

Supervisor Damon Connolly stated;

“I think what we may end up grappling with a little bit is on one hand I fully get where the planning Commission is coming from and also a number of residents have weighed in… Where on one hand obviously we are very hesitant and very aware of issues with new development in fire hazard zones and of course also exacerbated if you have situations of narrow roads, which is quite often the case. On the other hand, fundamentally, we are talking about supporting a strategy we have embraced, in kind of a Marin way, toward affordable housing goals of prioritizing ADUs…. It was brought home to me looking at the maps that effectively if we cordon off essentially WUI, high fire, what are you left with in terms of where ADUs may be allowed?”

Supervisor Dennis Rodoni said;

“On the ADUs, you know the 20-foot-wide roadway makes a lot of sense but I’m just worried that it’s very very restrictive and we don’t have the data to support it in terms of what we need.”

Supervisor Katie Rice added;

“Given that we just talked about the RHNA.., I have the same concerns around the restrictions in the WUI area fire risk ... I appreciate the concerns and I think they are valid around access and egress in developed areas and I’m real glad that that Fire Study is being done. I think it is going to be really important, the Fire Study, but I’m wondering if frankly we were to include the language that the Planning Commission is recommending on the ADUs does that have any implications for when we go to trying to develop a RHNA and identify sites? I’m going through the maps that you provided and there are a lot of areas that would be precluded, right, by fire risk…”

Planning Director Tom Lai responded;

“I want to address Supervisor Rice’s question because as you know, in our Housing Element, in our strategy to meet the RHNA, we’ve always been able to use some of the ADUs, not a lot, and given that the numbers that we are facing are so large for the next 8 year cycle, I would be concerned if we make it too restrictive and curtail the ability for sufficient ADUs to be built because that will help… I just want the Board to be aware that there could be a chilling effect on our ability and the strategies and the tools we have to come up with sites to meet the next 8-year cycle target. And I am concerned about the cumulative effects of factoring in all the fire severity zones and the WUIs and our ability to have sufficient sites available to produce some ADUs that could help the County meet our RHNA numbers.”

Supervisor Stephanie Moulton-Peters expressed;

“My own opinion is that this issue of health and safety and wildfire evacuations is very serious as is the need to provide housing and that we are missing right now some real hard data about the road system that we have in Marin County that would allow us to make the kinds of determinations we are seeking to make here. And I think the Wildfire JPA (Joint Powers Authority) road and evacuation study will provide the data and the street inventory and the evaluation of the roadways that will allow us to make the findings more definitively. So, I’m going to weigh in that I’m in favor of treating ADUs differently depending on the roadway that they are serviced by but I would also be in favor of waiting to put that provision into our code until we’ve got the basis to do this fully nailed down through this study. That would be my comment. I want to appreciate the public comment and the seriousness of these concerns. I live in a Very High Fire Hazard Severity Zone with a narrow winding road. So, I live it personally and I think we have to really pin down the data we need.”

Supervisor Judy Arnold concurred;

“I agree with what Supervisor Moulton-Peters said.”

The Motion & Vote:

Finally, Supervisor Rice made a motion to strike almost all the regulations that restricted Accessory Dwelling Units (ADUs) in high fire risk areas. Supervisor Arnold seconded it.

The County’s Planning Manager summed up the motion;

“The changes are deleting restrictions for ADUs under Category 1, whether or not those are single family or multifamily for fire prone areas. And then, in all three other Categories, keeping the language except deleting the language ‘Wildlands Urban Interface’. So that it only applies to Very High Fire Hazard Severity Zones.”

Supervisor Connolly added;

“And then also noting the desire to come back with that additional study”.

The Board unanimously voted “Aye”.


Category 1 ADUs (the worst category) are now allowed everywhere in Unincorporated Marin, including in Environmentally Sensitive Areas (Wetlands Conservation Areas & Stream Conservation Areas), the Wildlands Urban Interface (WUI), High Fire Zones, and Very High Fire Hazard Severity Zones.

Category 1 requires ministerial approval and allows a homeowner, in single-family neighborhoods, to build, “by right”, a new detached backyard Accessory Dwelling Unit (ADU) up to 800-square-feet, 16-feet-high, with only four-foot side and rear setbacks. This is in addition to the homeowner being able to convert a room within the single-family residence into a third living space (Junior Accessory Dwelling Unit - JADU). The new ADU could also be a converted garage, office or spare room. The size of the new ADU can be over and above the existing allowable square footage (AKA Floor Area Ratio - FAR) for the primary home.

Moreover, parking requirements are precluded in almost all scenarios. If a garage is converted to a dwelling unit, then there is no requirement for additional off-street parking to be provided. The result would be absolutely no off-street parking for the ADU, JADU and the main single-family home. All residents would have to park on the street.

Furthermore, Category 1 allows owners of multifamily housing complexes to build, “by right”, multiple Accessory Dwelling Units (up to 25% of the total existing legal units) in the existing legal building area of a multi-family dwelling that are not conditioned to be habitable, such as boiler rooms, storage rooms, passageways, attics, basements, and garages. Again, any off-street parking which is lost due to being converted to ADUs is not required to be replaced.


Supervisor Connolly's comment about coming back when the study is done wasn't clear. Will the Supervisors just look at the Marin Wildfire Prevention Authority’s roadway safety study when it is done? OR Will Planning Staff come back with specific recommendations on how to modify the development code in regard to restricting ADUs on inadequate and unsafe roadways in Fire Hazard Areas? This wasn’t clarified.

The Planning Commission’s recommended protections prohibited ministerial (automatic), “by right” approval of all categories of ADUs at properties located on roadways less than 20-feet-wide, which are also located in the Wildlands Urban Interface (WUI) or in a Very High Fire Hazard Severity Zone (VHFHSZ). However, a homeowner could still have applied for an Accessory Dwelling Unit permit at these locations and sought a variance or waiver of the prohibition, which could be granted if the local Fire Protection District determined that adequate emergency access and evacuation routes would be provided. Therefore, ADUs were still allowed everywhere in the County, including hazardous areas, if they met safety standards. It is unclear whether or not the Supervisors realized this.


Due to the fact that the Board of Supervisors made revisions to the Development Code Amendments pertaining to Accessory Dwelling Unit regulations, this issue should come back to the Supervisors and be placed on their Consent Calendar.

Therefore, comments can still be sent to the Supervisors asking them to pull approval of the Development Code Amendments from their Consent Calendar, and instead reconsider the Accessory Dwelling Unit regulations.

Please send comments to:

Board of Supervisors:

Planning Manager Jeremy Tejirian:

**Many thanks to everyone who sent letters/emails to the Supervisors regarding this issue and attended the Board of Supervisors' January 26th public hearing! Please continue your advocacy.

Together we can make a difference!


Accessory Dwelling Units, Marin County Supervisors, AB-68, Sustainable TamAlmonte