Berkeley Municipal Code Ch. 23.306 Accessory Dwelling Units

This Chapter establishes accessory dwelling unit (ADU) and junior accessory dwelling unit (Junior ADU) standards that:

A. Implement California Government Code Sections 66314 through 66339.

B. Increase overall supply and range of housing options in Berkeley.

C. Expedite small-scale infill development.

D. Support Housing Element goals of facilitating construction of accessory dwelling units and increasing the number of housing units that are more affordable to Berkeley residents.

E. Encourage development of accessory dwelling units in zoning districts with compatible land uses and infrastructure. (Ord. 7983-NS § 1, 2025; Ord. 7955-NS § 19, 2025; Ord. 7888-NS § 8, 2023; Ord. 7799-NS § 1, 2022; Ord. 7797-NS § 1, 2022; Ord. 7787-NS § 2 (Exh. A), 2021)

A. The provisions of this chapter apply to zoning districts where residential uses are permitted, on lots that have at least one existing or proposed Dwelling Unit or Group Living Accommodation that is not a Fraternity House, Sorority House or Dormitory.

B. Number Permitted. See Table 23.306-1--ADU and Junior ADU Maximum Number of Units per Lot.

C. Density Exemption and Growth Limits. ADUs are considered an accessory use consistent with the parcel’s General Plan and zoning designation, shall not count toward the allowable density, and shall not be subject to any local ordinance, policy, or program that limits residential growth.

Table 23.306-1. ADU AND JUNIOR ADU MAXIMUM NUMBER OF UNITS PER LOT

1New Construction ADUs may be either attached or detached from the main building(s) and/or other ADUs, in any configuration.

(Ord. 7983-NS §§ 2, 4, 2025; Ord. 7888-NS § 8, 2023; Ord. 7799-NS § 1, 2022; Ord. 7797-NS § 1, 2022; Ord. 7787-NS § 2 (Exh. A), 2021)

A. Basic Standards. See Table 23.306-2: ADU Development Standards.

Table 23.306-2. ADU DEVELOPMENT STANDARDS

1. Existing Building or Accessory Conversion. An ADU created entirely through conversion with no modifications to the existing building or accessory structure envelope that exceeds the development standards for maximum gross floor area in Table 23.306-2, ADU Development Standards, is allowed a physical addition of no more than 150 square feet. The addition must comply with maximum height and setback requirements.

2. Duplex or Multi-Unit Dwelling Conversion. Interior ADU(s) must be created entirely through non-habitable residential portions of an existing main building that are not within the living space of a dwelling unit (e.g. basement, attic, garages, storage room).

3. Accessory Building or Accessory Structure Conversion. An ADU converted from an accessory building or accessory structure is allowed to maintain non-conformity to the same location and dimensions of the existing accessory building or accessory structure, provided that the ADU meets fire and safety standards set forth in the California Building Standards Code adopted in BMC Title 19. Any physical additions to the existing accessory building or accessory structure shall comply with the development standards in Table 23.306-2 ADU Development Standards.

4. Attached ADU. An ADU shall be considered attached if sharing a common wall with a primary dwelling.

5. Detached ADU Setback Exceptions. If there is a lesser setback allowed in 23.304.060--Accessory Buildings and Enclosed Accessory Structures for a comparable accessory building or accessory structure in the underlying zoning district, that setback shall apply.

6. Attached ADU, New Construction Height. Attached ADUs with height up to 25 ft. allowed with a Zoning Certificate.

B. Junior ADUs.

1. Basic Standards. A Junior ADU shall be contained entirely within an existing or proposed single family dwelling (including basements, attics, storage rooms, boiler rooms, and passageways) or its attached garage, and have no more than 500 square feet in floor area.

2. Shared Sanitation Facility. If a Junior ADU shares a sanitary facility with a single-family dwelling, an internal connection between the Junior ADU and the main living area of the single family dwelling is required.

3. Junior ADU Floor Area. The Junior ADU gross floor area calculation excludes any shared sanitation facility with the single family dwelling.

C. Projections.

1. Outside of the Hillside Overlay. Chimneys, water heater enclosures, flues, heating and cooling equipment, eaves, cornices, canopies, awnings, bay windows, and balconies may project two feet into the required setbacks, so long as there remains at least a two-foot setback from property lines. Bay windows and balconies may not project into a required rear ADU setback.

2. Within the Hillside Overlay. No projections shall be allowed within a required setback.

D. Rooftop Decks. Roofs on ADUs may be designed, converted, or used as usable open space with a maximum additional height allowance of nine feet (beyond the height maximum allowed by development standards) only to enable rooftop access and protective railings. (Ord. 8007-NS § 14, 2026; Ord. 7983-NS §§5--8, 2025; Ord. 7955-NS §§ 20--23, 2025; Ord. 7888-NS § 8, 2023; Ord. 7799-NS § 1, 2022; Ord. 7797-NS § 1, 2022; Ord. 7787-NS § 2 (Exh. A), 2021. Formerly 23.306.040)

A. Zoning Certificate. An application for an ADU or Junior ADU shall be allowed with a Zoning Certificate. The review must be completed, and the application approved or denied, within 60 days of receipt of a completed application. A completed application must include evidence of compliance with this Chapter, including development standards.

1. If an application to create an ADU or Junior ADU is submitted as part of a project that requires discretionary review, a Zoning Certificate for a building permit shall not be issued for the ADU or Junior ADU until the discretionary approval(s) has/have been granted and any applicable appeal periods have expired. See 23.404.060(A) Post-Decision Provisions (Effective Dates).

2. Issuance of a Zoning Certificate shall not be denied for the construction or conversion of an ADU or Junior ADU that complies with the requirements of Government Code Section 66323.

3. Issuance of a Zoning Certificate for the construction or conversion of an ADU or Junior ADU shall not be denied based on the failure of an applicant to correct a nonconforming zoning condition.

4. If the Zoning Officer denies an application, the applicant shall be provided, within the same 60-day period, a written notice identifying all deficiencies in the application and a description of how the application may be corrected.

B. Neighbor Noticing.

1. Scope and Timing of Notice. Notice of an ADU application shall be mailed to tenants of the subject property, and owners and tenants of the adjacent, confronting, and abutting properties, within ten working days of submission of the building permit application to the City.

2. Content of Notice. Notice shall provide the address of the project, allowable hours of construction, a link to the City’s ADU webpage, and information for tenants of the subject property on how to contact a Rent Board Housing Counselor by e-mail or phone and any other resource information deemed relevant.

3. Mailing Fees. The applicant shall be responsible for the cost of materials, postage, and staff time necessary to process and mail notices.

C. Deed Restriction. The property owner shall file a deed restriction with the Alameda County Recorder which states:

1. The Junior ADU shall not be sold separately from the main building;

2. The ADU shall not be sold separately from the main building unless the conditions of BMC 23.306.040(D) ADUs Developed by a Qualified Nonprofit Developer are met;

3. The ADU and/or Junior ADU shall not be rented for a term that is shorter than 30 days; and

4. If the property includes a Junior ADU, the Junior ADU or the Single Family Dwelling in which the Junior ADU is located shall be owner-occupied. Owner-occupancy shall not be required if the JADU and the Single Family Dwelling do not share sanitation facilities, or if the owner is another governmental agency, land trust, or housing organization.

D. ADUs Developed by a Qualified Nonprofit Developer. An ADU built or developed by a "qualified nonprofit corporation" may be sold or conveyed separately from the main building to a "qualified buyer," as such terms are defined in subdivision (b) of Section 66340 of the California Government Code. The ADU must be held pursuant to a recorded tenancy in common agreement recorded on or after December 31, 2021 that includes the following elements:

1. Delineation of all areas of the property that are for the exclusive use of a cotenant;

2. Delineation of each cotenant’s responsibility for the costs of taxes, insurance, utilities, general maintenance and repair, and improvements associated with the property;

3. Procedures for dispute resolution among cotenants before resorting to legal action;

4. Allocates to each qualified buyer an undivided, unequal interest in the property based on the size of the dwelling each qualified buyer occupies;

5. A repurchase option that requires the qualified buyer to first offer the qualified nonprofit corporation to buy the ADU or primary dwelling if the buyer desires to sell or convey the property;

6. A requirement that the qualified buyer occupy the ADU or primary dwelling as the buyer’s principal residence; and

7. Affordability restrictions on the sale and conveyance of the ADU or primary dwelling that ensure the ADU and primary dwelling will be preserved for low-income housing for 45 years for owner-occupied housing units and will be sold or resold to a qualified buyer.

8. If requested by a utility providing service to the primary residence, the ADU shall have a separate water, sewer, or electrical connection to that utility. (Ord. 8007-NS § 15, 2026; Ord. 7999-NS § 2, 2026; Ord. 7983-NS §§9--11, 2025; Ord. 7955-NS §§ 24--26, 2025; Ord. 7888-NS § 8, 2023; Ord. 7799-NS § 1, 2022; Ord. 7797-NS § 1, 2022. Formerly 23.306.030)