Regulatory Barriers Are Reduced For Ag ADUs and Other Housing Statewide

Written By: Gary Quackenbush
Published: November 4, 2019

The lack of adequate and affordable housing has reached a critical tipping point in California, prompting a series of landmark decisions made locally in Sonoma County as well as in Sacramento in September and October designed to eliminate regulatory constraints to housing development. These actions also make it easier to obtain approvals for Accessory Dwelling Units (ADU) –even on some agricultural parcels in Z Combining Districts previously excluded.


Lifting Z District Restrictions

On Tuesday, September 17, the Sonoma County Board of Supervisors approved an ordinance that removed zoning restrictions that prohibited owners of over 1,924 agricultural properties from applying for permits to construct Accessory Dwelling Units (ADU). This ordinance went into effect on October 17.

While ADUs are a permitted use in agricultural zones LIA, LEA and DA, back in 1993 the Sonoma County Board of Supervisors created the Z Combining District to limit ADUs where site constraints (lack of water, septic, etc.) may prevent their development and use.

This restriction was also applied to agricultural parcels to limit non-farm uses and to preserve agriculture activity in these areas. Today, site conditions among certain agricultural properties have improved, leading to a reassessment of those parcels within the Z District.

Of some 11,000 farm parcels in Sonoma County, 4,000 of the 6,000 ag parcels included in the Z District were re-evaluated. Of the 4,000 parcels, about half were screened out as inappropriate for building ADU’s based on the following criteria:

  • The property is located within a high or very high fire hazard severity zone;
  • The property is within a critical biotic habitat area for the California Tiger Salamander;
  • An ADU on the parcel does would present the potential for groundwater contamination;
  • An ADU on the parcel could unduly contribute to declining groundwater levels;
  • The property is located in a Traffic Sensitive Combining Zone;
  • The property is subject to a Land Conservation (Williamson Act) or other open-space contract, or other recorded agricultural easements, and the property is not located in the Coastal Zone.

Following the creation of the Z District, owners of 40 agricultural parcels applied to build ADUs. These applications were examined on a case-by-case basis using updated data and new findings that surfaced during the review process.  The rest of the 1,900 Ag parcel owners are still eligible to apply.

However, this does not mean ADUs are always feasible within rezoned properties. ADU applicants must show that they can meet eligibility requirements and demonstrate consistency with standards established in the Zoning Code.

That said, it is estimated that an ADU might not be feasible on 30-40 percent or more of approximately 1,900 rezoned parcels due to groundwater availability, septic capacity, access, parcel size and other factors.

Ag property owners are encouraged to discuss site-specific factors with Permit Sonoma staff members to determine if their parcel is eligible for an ADU. For additional information, go to


First Ag Parcel ADU

Sebastopol residents Tor Allen and his wife were the first family to get an ADU approval (known then as a “granny unit”) a decade ago on a 10-acre apple farm parcel that was divided giving them a 2.4-acre lot. Their application was among the earliest to be reviewed on a case-by-case basis following the creation of the Z District.

“Our goal was to construct a 600-square foot single-story detached building behind our main house for a senior family member. Back in 2009, fees totaled between $3,000 and $5,000 and it only took about three months to navigate the permitting process. Following the recession, there wasn’t a lot of construction activity. However, it was not a foregone conclusion that we would be approved. We had to petition the Board of Supervisors and the planning department.”

They built their primary residence and the ADU by 2011.

Tor is a former PG&E employee who worked in a clean energy planning group before establishing his own consulting business, the Rahus Institute, providing solutions for a sustainable world.  This non-profit focuses on educating the next generation on the benefits of housing energized by the sun through its Solar Schoolhouse presentations in schools and to other organizations.

Well before the devastating 2017-18 wildfires, the Allen’s ADU was built with energy efficiency and fire protection in mind. It has Hardie board siding, and a metal roof covered with solar panels. Walls were framed off-site and delivered, saving weeks of construction time.

Supervisors Weigh In

According to Sonoma County Board of Supervisors Chair David Rabbitt, “Allowing Accessory Dwelling Units provides viable housing options and supports sustainable agriculture.”

However, today, relatively high costs estimated at $15,000 to $20,000 are associated with ADU permit fees — which can rise to between $18,000 and $35,000 if a site is on public water/sewer systems. Add this to the length of the approval process – that can take over a year – plus the cost of building an ADU, and key challenges still remain.

According to Supervisor James Gore, other regulatory and political barriers are still with us, but “growth should not be managed with fees and time delays.”

Supervisor Shirlee Zane said, “There is no question about the need for housing. During the next fiscal year, I want to take a closer look at standards in place for qualifying new ag housing units.”

She mentioned that farmers say ADUs can provide supplemental income, housing for farm families as well as for aging parents.

Supervisor Susan Gorin observed, “We need to find creative ways to add more housing without doing additional CEQA reviews.”

She added that according to state sources, ADUs in general fit within the existing fabric of housing growth without a significant or deleterious impact on neighborhoods. Supervisor Gorin also noted that ADUs bring flexibility through occupancy by owners, by renting them out for the long term or by renting the primary dwelling.

Supervisor Lynda Hopkins commented that ag housing thresholds are outdated that a set number of farm dwellings are allowed according to the number of cows, hens, sheep, etc., on the property.  She asked, “Are ADUs actually increasing density or just swapping one form of housing for another?”

In addition to ag parcels, throughout Sonoma County, Permit Sonoma reports that some 1,200 to 1,300 ADUs also have been approved to date on non-farm parcels in unincorporated areas.

18 New Housing Laws Signed

On October 9, Governor Gavin Newsom signed 18 laws designed to further increase housing production statewide by reducing the power of cities to block new housing development and by making it easier to build ADUs.  Five of the 18 laws focus on ADUs.  The following is a brief synopsis of each new ADU law:

AB 68:  Includes changes making the development of more ADUs easier while reducing barriers to ADU approval and construction.

AB 587:  Allows sale of ADUs separately from primary residences, as a narrow exemption for affordable housing organizations to sell deed-restricted land to eligible homeowners with low incomes.

AB 671:  Requires that local government housing plans encourage ADU rentals that are affordable and requires State legislators to develop a list of state grants and financial incentives for affordable ADUs.

AB 881:  Removes obstacles to ADU construction by restricting local jurisdictions’ permitting criteria and stating that ADUs must receive streamlined construction if built-in existing garages and eliminates local municipalities’ ability to require owner-occupancy for five years.

SB13: Creates a tiered fee structure that charges ADUs more fairly based on their size and location, while also lowering the application approval timeframe, establishing a way to get unpermitted ADUs up to code, and strengthening an enforcement mechanism allowing the State to ensure that municipalities are complying with the ADU statute.

While campaigning for governor, Gavin Newsom went on record saying he wanted to see 3.5 million new homes built by 2025. His 2019 budget, signed in June, includes a historic $2.75 billion investment for housing — $1 billion to address homelessness and $1.75 billion to build more homes in the state.

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