Chapter 19.45

ACCESSORY DWELLING UNITS

Sections:

• 19.45.010 Purpose. 19.45.020 Effect of conforming. 19.45.030 General ADU and JADU requirements. 19.45.040 ADU permit development standards. 19.45.050 Reserved. 19.45.060 Approval process. 19.45.070 Nonconforming ADUs and discretionary approval.

The Sonoma Municipal Code is current through Ordinance 13-2025, passed December 3, 2025.

Page 232 of 410

Title 19 Integrated Development Regulations and Guidelines | Sonoma Municipal Code

• 19.45.080 Termination of permit and use for ADUs and JADUs.

• 19.45.090 Violations and enforcement.

The purpose of this chapter is to allow and regulate accessory dwelling units (ADUs) and junior accessory dwelling units (JADUs) in compliance with California Government Code Sections 65852.2 and 65852.22 and to encourage the development of affordable housing. (Ord. 04-2023 § 1(B), 2023).

An ADU or JADU that conforms to the standards in this chapter will not be:

• A. Deemed to be inconsistent with the city’s General Plan and zoning designation for the lot on which the ADU or JADU is located.

• B. Deemed to exceed the allowable density for the lot on which the ADU or JADU is located.

• C. Considered in the application of any local ordinance, policy, or program to limit residential growth.

• D. Required to correct a nonconforming zoning condition. This does not prevent the city from enforcing compliance with applicable building standards in accordance with Health and Safety Code Section 17980.12. (Ord. 04-2023 § 1(B), 2023).

A. Fire Sprinklers. Fire sprinklers are required in an ADU if sprinklers are required in the primary residence; provided, however, that construction of an ADU shall not trigger a requirement for fire sprinklers to be installed in the existing primary dwelling.

• B. Rental Term. No ADU or JADU may be rented for a term that is shorter than 30 days.

• C. No Separate Conveyance. An ADU or JADU may be rented, but no ADU or JADU may be sold or otherwise conveyed separately from the lot and the primary dwelling (in the case of a single-family lot) or from the lot and all of the dwellings (in the case of a duplex or multifamily lot).

D. Septic System. If the ADU or JADU will connect to an existing on-site water treatment system, the owner must include with the application a percolation test completed within the last five years or, if the percolation test has been recertified, within the last 10 years.

• E. Owner Occupancy.

The Sonoma Municipal Code is current through Ordinance 13-2025, passed December 3, 2025.

Page 233 of 410

Title 19 Integrated Development Regulations and Guidelines | Sonoma Municipal Code

1. All ADUs permitted before January 1, 2020, are subject to the owner-occupancy requirement that was in place when the ADU was permitted.

2. All JADUs are subject to an owner-occupancy requirement. A natural person with legal or equitable title to the property must reside on the property, in either the primary dwelling or JADU, as the person’s legal domicile and permanent residence. However, the owner-occupancy requirement of this subsection does not apply if the property is entirely owned by another governmental agency, land trust, or housing organization.

F. Deed Restriction. Prior to issuance of a building permit for an ADU or JADU, a deed restriction must be recorded against the title of the property in the county recorder’s office and a copy filed with the planning and community services director. The deed restriction must run with the land and bind all future owners. The form of the deed restriction will be provided by the city and must provide that:

1. The ADU or JADU may not be sold separately from the primary dwelling.

2. Owner-occupancy is required for parcels with a JADU, consistent with subsection (E)(2) of this section.

3. The deed restriction runs with the land and may be enforced against future property owners.

4. The deed restriction is enforceable by the planning and community services director or his or her designee for the benefit of the city. Failure of the property owner to comply with the deed restriction may result in legal action against the property owner, and the city is authorized to obtain any remedy available to it at law or equity, including, but not limited to, obtaining an injunction enjoining the use of the ADU or JADU in violation of the recorded restrictions or abatement of the illegal unit. (Ord. 04-2023 § 1(B), 2023).

The following requirements apply only to ADUs that require an ADU permit under SMC 19.45.060(B)

• A. Maximum Size.

  1. The maximum size of a detached or attached ADU requiring an ADU permit is 850 square feet for a studio or one-bedroom unit and 1,000 square feet for a unit with two bedrooms. No more than two bedrooms are allowed.

2. Application of other development standards may further limit the size of the ADU, but the application of development standards that impose limits on lot coverage, floor area ratio, open space, front setbacks, and minimum lot size shall not require an attached or detached ADU to be less than 800 square feet with a minimum four-foot side and rear yard setback.

B. Floor Area Ratio (FAR) and Site Coverage. An ADU shall conform to all site coverage and floor area ratio regulations applicable to the zoning district in which the property is located but no application of FAR or site coverage standards requirements may require the ADU to be less than 800 square feet.

The Sonoma Municipal Code is current through Ordinance 13-2025, passed December 3, 2025.

Page 234 of 410

Title 19 Integrated Development Regulations and Guidelines | Sonoma Municipal Code

C. Setbacks.

1. No setback is required for a legally constructed existing living area or accessory structure or a structure constructed in the same location and to the same dimensions as a legally constructed existing structure that is converted to an accessory dwelling unit or to a portion of an accessory dwelling unit.

2. A minimum setback of four feet from the side and rear lot lines is required for detached and attached ADUs.

3. Front and street-side setbacks shall comply with those established in the zoning district where the parcel is located. Detached accessory dwelling units shall comply with front and street-side setback restrictions for accessory structures while attached accessory dwelling units shall comply with front setback restrictions for primary structures. However, where the imposition of front or street-side setbacks under this subsection would prohibit the development of an ADU of at least 800 square feet on the parcel, front and street-side setbacks shall be a minimum of four feet.

• D. Height.

  1. Lots With an Existing or Proposed Single-Family Dwelling Unit.

a. A single-story detached ADU shall not exceed 16 feet in height above grade, measured to the peak of the structure.

b. An attached ADU shall not exceed the maximum allowable height of the primary dwelling as allowed by the underlying zoning development requirements.

c. A two-story detached ADU shall not exceed 25 feet measured from the finished grade to the highest point of the roof. Additionally, one-story walls shall not exceed a plate height of 12 feet above finished grade, two-story walls shall not exceed an overall plate height of 20 feet above finished grade, and the plate height on any new second story shall not exceed eight feet.

2. Lots With a Proposed or Existing Duplex or Multifamily Dwelling Unit.

• a. A detached accessory dwelling unit shall not exceed 18 feet on a lot with an existing or proposed multifamily, multistory dwelling.

b. A single-story detached ADU shall not exceed 16 feet in height above grade, measured to the peak of the structure.

c. An attached ADU may not exceed the height of the primary dwelling as allowed by the underlying zoning development requirements.

d. A two-story detached ADU shall not exceed 25 feet measured from the finished grade to the highest point of the roof. Additionally, one-story walls shall not exceed a plate height of 12 feet above finished grade, two-story walls shall not exceed an overall plate height of 20 feet above finished grade, and the plate height on any new second story shall not exceed eight feet.

The Sonoma Municipal Code is current through Ordinance 13-2025, passed December 3, 2025.

Page 235 of 410

Title 19 Integrated Development Regulations and Guidelines | Sonoma Municipal Code

E. An ADU shall include a kitchen and other permanent provisions for living and sleeping, including a closet or other reasonable storage.

• F. Lighting shall be shielded or directed so that it does not glare off site or illuminate any dwelling unit or adjacent property.

G. Windows shall be located to avoid line of sight to windows of adjacent properties. Obscured glass and other techniques may be used to avoid line of sight.

H. An ADU shall have a separate exterior access. The exterior access shall be a standard exterior door and shall be located in a manner that will preserve, to the greatest extent feasible, the privacy of the primary residence, other accessory structures, and any adjoining residences.

• I. A permanent foundation shall be required for all ADUs.

• J. Fees.

  1. Impact Fees.

     • a. No impact fee is required for an ADU that is less than 750 square feet in size.

b. Any impact fee that is required for an ADU that is 750 square feet or larger in size must be charged proportionately in relation to the square footage of the primary dwelling unit (e.g., the floor area of the primary dwelling, divided by the floor area of the ADU, times the typical fee amount charged for a new dwelling). “Impact fee” here does not include any connection fee or capacity charge for water or sewer service.

2. Utility Fees.

a. Converted ADUs and JADUs on a single-family lot, created under SMC 19.45.060(A)(1), are not required to have a new or separate utility connection directly between the ADU or JADU and the utility main. A connection fee or capacity charge shall not be required unless the ADU or JADU is constructed with a new primary dwelling.

b. All ADUs and JADUs not covered by subsection (J)(2)(a) of this section require a new, separate utility connection directly between the ADU or JADU and the utility. The connection is subject to a connection fee or capacity charge that is proportionate to the burden created by the ADU or JADU, based on either the floor area or the number of drainage-fixture units (DFU) values, as defined by the California Plumbing Code, upon the water or sewer system. The fee or charge may not exceed the reasonable cost of providing this service. (Ord. 04-2023 § 1(B), 2023).

The Sonoma Municipal Code is current through Ordinance 13-2025, passed December 3, 2025.

Page 236 of 410

Title 19 Integrated Development Regulations and Guidelines | Sonoma Municipal Code

A. Building Permit Only. If an ADU or JADU complies with each of the general requirements in SMC 19.45.030 (General ADU and JADU requirements), it is allowed with only a building permit in the following scenarios:

1. ADU Established from Existing Converted Space – Single-Family. Only one ADU or JADU on a lot with a proposed or existing single-family dwelling on it, where the ADU or JADU:

   • a. Is either: within the space of a proposed single-family dwelling; within the existing space of an existing single-family dwelling; or within the existing space of an accessory structure, plus up to 150 additional square feet if the expansion is limited to accommodating ingress and egress.

   • b. Has exterior access that is independent of that for the single-family dwelling.

   • c. Has side and rear setbacks sufficient for fire and safety, as dictated by applicable building and fire codes.

2. New Detached ADU – Single-Family. One detached, new-construction ADU on a lot with a proposed or existing primary residence (in addition to any JADU that might otherwise be established on the lot under subsection (A)(1) of this section), if the detached ADU satisfies the following limitations:

   • a. The side and rear yard setbacks are at least four feet.

   • b. The total floor area is 800 square feet or smaller.

   • c. The peak height above grade is 16 feet or less.

3. ADU Established From Existing Converted Space – Multifamily. ADUs may be created within portions of existing multifamily dwelling structures that are not used as livable space, including but not limited to storage rooms, boiler rooms, passageways, attics, basements, or garages, if each converted ADU complies with state building standards for dwellings. At least one converted ADU is allowed within an existing multifamily dwelling, and up to 25 percent of the existing multifamily dwelling units may each have a converted ADU under this subsection.

4. New Detached ADU – Multifamily and Duplexes. No more than two detached ADUs on a lot that has an existing or proposed duplex or multifamily dwelling if each detached ADU satisfies the following limitations:

• a. The side and rear yard setbacks are at least four feet. If the existing multifamily dwelling has a rear or side setback of less than four feet, no modification of the existing multifamily dwelling shall be

The Sonoma Municipal Code is current through Ordinance 13-2025, passed December 3, 2025.

Page 237 of 410

Title 19 Integrated Development Regulations and Guidelines | Sonoma Municipal Code

required as a condition of approving the application to construct an accessory dwelling unit that satisfies the requirements of this subsection.

  - b. The total floor area is 800 square feet or smaller. 

  - c. Complies with the height limit in SMC 19.45.040(D)(2)(a) or (b). 

• B. ADU Permit Required.

  1. Except as allowed under subsection (A) of this section, no ADU may be created without a building permit and an ADU permit in compliance with the standards set forth in SMC 19.45.030 (General ADU and JADU requirements) and 19.45.040 (ADU permit development standards).

2. The city may charge a fee to reimburse it for costs incurred in processing ADU permits, including the costs of adopting or amending the city’s ADU ordinance. The ADU permit processing fee is determined by the planning and community services director and approved by the city council by resolution.

• C. Process and Timing.

  1. An ADU permit is considered and approved ministerially, without discretionary review or a hearing.

  2. The city must approve or deny an ADU permit application or building permit application to create an ADU or JADU within 60 days from the date that the city receives a completed application, unless either:

     • a. The applicant requests a delay, in which case the 60-day time period is tolled for the period of the requested delay; or

     • b. In the case of a JADU and the application to create a junior accessory dwelling unit is submitted with a permit application to create a new single-family dwelling on the lot, the city may delay acting on the permit application for the JADU until the city acts on the permit application to create the new singlefamily dwelling, but the application to create the JADU will still be considered ministerially without discretionary review or a hearing. (Ord. 04-2023 § 1(B), 2023).

Any proposed ADU or JADU that does not conform to the objective standards set forth in SMC 19.45.010 through 19.45.060 may be allowed by the city with a use permit, in accordance with the other provisions of this title. (Ord. 04-2023 § 1(B), 2023).

The Sonoma Municipal Code is current through Ordinance 13-2025, passed December 3, 2025.

Page 238 of 410

Title 19 Integrated Development Regulations and Guidelines | Sonoma Municipal Code

A. No building permit shall be issued to remove permanent features of an ADU, including the provisions for eating, cooking and sanitation, and separate exterior entrance, until written approval to terminate the use of living space as an ADU or JADU is granted by the planning and community services director or his or her designee.

B. At its discretion, the planning and community services director may grant an owner’s written request to terminate an ADU or JADU and deed restriction. The planning and community services director shall consider the length of time such permit has been in force, the conditions of approval, the exceptions granted for the ADU or JADU, and the impact on the city’s affordable housing supply.

C. As a condition of termination, the planning and community services director shall require the owner to make modifications to the property to comply with: (1) current building code requirements and (2) current development standards in effect at the time the request is made to terminate use, including but not limited to setbacks, height, parking and floor area. The owner shall apply for a building permit to make such modifications as required by the city’s building and fire codes. (Ord. 04-2023 § 1(B), 2023).

A. It is unlawful for any person to violate any provision or to fail to comply with any of the requirements of this chapter. An ADU or JADU will be found in violation of this chapter when the dwelling unit has been created without the required city approvals, or does not comply with standards and deed restrictions established in this chapter. Violations are subject to the enforcement penalties and procedures of Chapter 1.28 SMC.

B. In addition to the enforcement penalties and procedures included in Chapter 1.28 SMC, the city may pursue any remedies provided by law against the owner of an ADU or JADU found to be in violation of this chapter, or an ADU or JADU not maintained in conformance with this chapter, including:

1. Revocation of the ADU or JADU permit;

2. Where an ADU or JADU has been improperly terminated and is being used as habitable space for the primary dwelling, removal of the floor area serving as habitable space may be required; and

3. In any civil enforcement action, the city is entitled to recover attorneys’ fees and costs from an owner who is determined to have an illegal ADU or JADU, or is in violation of this chapter. (Ord. 04-2023 § 1(B), 2023).