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2. 30-5.18 - Accessory Dwelling Units.
Purpose. This Section provides for the creation of accessory dwelling units and junior accessory dwelling units on lots zoned to allow residential use consistent with Government Code Sections 65852.2, 65852.22, and 65852.26. Such accessory dwelling units contribute needed housing to the community while maintaining neighborhood character, support affordable housing and multigenerational living, and enhance housing opportunity near transit. An accessory dwelling unit that conforms to the development and design standards in this section shall:
Be deemed an accessory use or an accessory building and not be considered to exceed the allowable density for the lot upon which it is located; Be deemed a residential use that is consistent with the existing General Plan and zoning designation for the lot upon which it is located;
Not be considered in the application of any ordinance, policy, or program to limit residential growth; and
Not be considered a new residential use for the purposes of calculating connection fees or capacity charges for utilities, including water and sewer service.
Applicability. The provisions of this section authorize an accessory dwelling unit to be located on a lot in any zoning district where residential use is permitted or conditionally-permitted that includes a proposed or existing primary dwelling. Accessory dwelling units shall not be considered primary units and shall be exempt from any residential density standard established by the subject zoning district.
Development Standards. An accessory dwelling unit may be attached to, or located within, the proposed or existing primary dwelling, including attached garages, storage areas or similar uses, or an accessory structure, or detached from the proposed or existing primary dwelling and located on the same lot as the proposed or existing primary dwelling.
Number and Type Allowed:
Single-family lots. On lots with an existing or proposed single-family dwelling, one (1) accessory dwelling unit and one (1) junior accessory dwelling unit are permitted.
Multi-family lots. On lots with existing multifamily dwellings (two (2) or more units), any number of accessory dwelling units are permitted within portions of an existing building, as long as each unit complies with state building standards for dwellings. In addition to the attached units allowed by subsection (1), two (2) accessory dwelling units detached from the primary dwelling(s) are permitted on a multi-family lot. The two (2) detached accessory dwelling units may be constructed to be attached to each other. 8/6/26, 9:27 AM Alameda, CA Code of Ordinances
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Exhibit 1
3. (a)
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(1)
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(1)
Maximum Size: The size of an accessory dwelling unit shall not exceed one thousand two hundred (1,200) square feet. Nothing in this section shall be interpreted to prohibit at least an eight hundred (800) square foot accessory dwelling unit that is sixteen (16′) feet in height with four (4′) foot side and rear yard setbacks to be constructed in compliance with all other development standards.
Attached Accessory Dwelling Units: An accessory dwelling unit that is attached to or created within a proposed or existing primary dwelling shall comply with all height, building coverage, yard areas, and setback requirements for the primary dwelling.
Independent Access: Exterior access shall be provided independently from the primary dwelling.
Unit Separation: Attached units and units that are within the primary dwelling may maintain an interior connection to the primary dwelling provided there is a fire-rated door separating the units that is lockable on both sides.
Aggregate Lot Coverage: The aggregate lot coverage of all building footprint(s) on the lot shall not exceed sixty (60) percent.
Detached Accessory Dwelling Units: An accessory dwelling unit may be constructed as a new detached structure or created through the conversion of an existing accessory structure and shall comply with the following requirements:
Maximum Height: Eighteen (18′) feet. An additional two (2) feet in height shall be permitted, raising the maximum height limit to twenty (20) feet, when the roof pitch on the accessory dwelling unit matches the roof pitch of the primary dwelling unit.
On lots located within the special flood hazard area, as defined by FEMA's Flood Insurance Rate Maps (FIRM), the height of a detached accessory dwelling unit may exceed eighteen (18′) feet by the minimum amount necessary, as determined by the Building Official and City Engineer, to allow:
A finished floor of the habitable space at one (1′) foot above the Base Flood Elevation shown on the FIRM; and
Up to eight (8′) feet in vertical clearance from the finished floor to ceiling within the habitable space; and
A roof pitch that matches the roof pitch of the primary dwelling unit.
Required Setbacks from Side and Rear Property Lines:
No setbacks shall be required for an existing accessory structure or a new structure constructed in the same location and to the same dimensions as an existing structure that is converted to an accessory dwelling unit. For purposes of this subsection, dimensions shall mean the exterior width, length, and height of the existing accessory structure up to eighteen (18′) feet.
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(2)
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A setback of four (4′) feet from the side and rear lot lines shall be required for an accessory dwelling unit that is not converted from an existing structure or new structure constructed in the same location and to the same dimensions as an existing structure.
Notwithstanding subsection (2) above, the side and rear yard setbacks may be reduced to zero (0′) feet if all of the following conditions are met:
The detached ADU is located seventy-five (75′) feet or more from the front property line and, if applicable, five (5′) feet from the street side of a corner lot; The portion of the neighboring lot(s) that adjoin the detached ADU is not within seventy-five (75′) feet of the neighboring lots' front property line(s); All construction within three (3′) feet of the property line, including eaves and similar architectural features, is one (1) hour fire resistive as required by the Alameda Building Code or as approved by the Building Official; Notwithstanding subsection (a), the detached ADU is not more than sixteen (16′) feet in height; and
The detached ADU will not cover more than sixty (60%) percent of the minimum required rear yard as prescribed by the subject zoning district, with a minimum allowed coverage area of six hundred (600) square feet. This requirement shall not apply to an accessory dwelling unit constructed in the same location and to the same dimensions as an existing accessory structure that is converted to an accessory dwelling unit.
Minimum Separation from Other Structures: There shall be a minimum of six (6′) feet separating all construction (including eaves and similar architectural features) of the detached ADU from the main building(s) or other accessory building(s) on the same lot.
The separation requirements of this paragraph may be reduced by the Building Official if one (1) hour fire resistive construction is utilized.
Lot Coverage: The aggregate lot coverage of all building footprint(s) on the lot shall not exceed sixty (60%) percent. This requirement shall not apply to an accessory dwelling unit constructed in the same location and to the same dimensions as an existing accessory structure that is converted to an accessory dwelling unit. This requirement shall also not be interpreted to prohibit at least an eight hundred (800) square foot accessory dwelling unit that is up to eighteen (18′) feet in height with four (4′) foot side and rear yard setbacks to be constructed in compliance with all other development standards.
Expanding an Existing Accessory Structure: An accessory dwelling unit created within an existing accessory structure may include an expansion of not more than one hundred fifty (150) square feet beyond the same physical dimensions as the existing accessory 8/6/26, 9:27 AM Alameda, CA Code of Ordinances
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structure. An expansion beyond the physical limitations of the existing accessory structure shall be limited to accommodating ingress and egress.
Design Standards:
Attached Unit: The design of an attached accessory dwelling unit shall match the same materials, colors and style as the exterior of the primary dwelling, including roof form, materials and pitch, eaves, trim, and windows. Creation of the accessory dwelling unit shall not involve any changes to existing street-facing facades or raise the height of existing floor(s) and roof elevations. Entrances to the accessory dwelling unit shall not be located on a street-facing façade. The construction of the accessory dwelling unit shall not obscure, damage, destroy or remove any original architectural details or materials of an existing main building, except as necessary to construct and integrate the accessory dwelling unit.
Detached Unit: The design of a detached accessory dwelling unit located within fifty (50′) feet of an adjacent street frontage shall incorporate the exterior features of the primary dwelling, including siding, roof form, eaves, and window type, trim and orientation. This subsection shall not be interpreted to prohibit a prefabricated structure or manufactured home, as defined in Section 18007 of the California Health and Safety Code.
Converted Accessory Buildings and Garages: Existing accessory buildings such as detached garages that are converted to accessory dwelling units shall replace garage doors with the same exterior wall material, building color, and window trim as the existing building or the primary dwelling structure if the accessory dwelling unit is being created in a garage attached to the primary dwelling.
Junior Accessory Dwelling Units: One (1) junior accessory dwelling unit shall be permitted ministerially if complying with the standards of subsection c.1., c.3(a), and c.3(b) above, and the following:
The junior accessory dwelling unit shall be fully located within an existing or proposed primary single-family dwelling, except an addition of up to one hundred fifty (150) square feet may be permitted as part of an application for a junior accessory dwelling unit.
The unit shall be no larger than five hundred (500) square feet in floor area.
The unit may maintain an interior connection to the primary dwelling and shall provide an exterior entrance separate from the main dwelling entrance.
The unit may contain separate sanitation facilities or may share with the primary dwelling.
The unit shall include an efficiency kitchen that shall include the following components:
A cooking facility with appliances; and
A food preparation counter and storage cabinets.
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(f)
(g)
(h)
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Notwithstanding subsection d. below, no additional parking shall be required for a junior accessory dwelling unit.
For purposes of providing service for water, sewer, or power, including a connection fee, a junior accessory dwelling unit shall not be considered a separate or new dwelling unit.
Before issuing a building permit for a junior accessory dwelling unit, the property owner shall file with the county recorder a declaration or an agreement of restrictions, which has been approved by the City Attorney as to its form and content, containing a reference to the deed under which the property was acquired by the owner and stating that:
The junior accessory dwelling unit shall not be sold or otherwise conveyed separately from the primary dwelling, and rental of a junior accessory dwelling unit shall be for a period longer than thirty (30) days.
The applicant shall be an owner-occupant of either the remaining portion of the primary dwelling or the newly created junior accessory dwelling unit. Owner- occupancy shall not be required if the owner is another governmental agency, land trust, or housing organization.
A restriction on the junior accessory dwelling unit size and attributes exists as required by subsection c.6, above.
Parking: Off-street parking provided shall comply with Section 30-7. When a garage, carport, or covered parking structure is demolished or converted in conjunction with the construction of an accessory dwelling unit, replacement of the parking space(s) shall not be required. The driveway and curb cut may remain for off-street parking provided the length of such driveway is at least eighteen (18′) feet, measured from the property line, in order to accommodate a parked vehicle without any portion of the vehicle encroaching into the public right-of-way. Remaining driveways that do not meet the minimum eighteen (18′) foot length shall be abandoned per Section 22-18.3 as part of the construction of the accessory dwelling unit.
Rental and Sale Limitations. The accessory dwelling unit shall not be sold or otherwise conveyed separately from the primary dwelling except as allowed pursuant to Government Code Section 65852.26, and rental of an accessory dwelling unit shall be for a period longer than thirty (30) days.
Application and Review Process.
Ministerial Review. Except as provided below, application for an accessory dwelling unit shall be reviewed ministerially within sixty (60) days from receipt of a completed application without discretionary review or public hearing when in compliance with the development standards of this section.
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Combination permits. For applications that combine a new accessory dwelling unit with improvements other than for the accessory dwelling unit, the non-accessory dwelling unit portion of the application shall be subject to design review if said improvement is not exempt from design review as provided by Section 30-37.2.
Vacant Lots. An accessory dwelling unit must be located on a lot with a proposed or existing primary dwelling. If the lot is undeveloped, then the applicant will be subject to discretionary review for construction of the primary dwelling.
The accessory dwelling unit shall meet the requirements of the building and housing code, as adopted and amended by the Alameda Building Code, that apply to detached dwellings, as appropriate. Except that fire sprinklers or fire attenuation shall not be required for an accessory dwelling unit if not required for the primary residence.
No protected tree(s) shall be removed to accommodate an accessory dwelling unit except with the recommendation of a certified arborist and approval procedures set forth in Section 13-21 of Chapter XIII of the Alameda Municipal Code.
Nothing in this section supersedes requirements for obtaining development permits pursuant to this chapter or for properties subject to the preservation of historical and cultural resources set forth in Section 13-21 of Chapter XIII of the Alameda Municipal Code, except that no public notice or discretionary review shall be required for the demolition of a detached garage or accessory structure that is to be replaced with an accessory dwelling unit, unless the property is located within a historic district.
Accessory dwelling units shall be exempt from the Improvement Tax provisions in AMC Section 3- 62, Improvement Tax.
(Ord. No. 3184 N.S., § 9, 7-5-2017; Ord. No. 3278 N.S., § 2, 5-5-2020; Ord. No. 3309 N.S., § 4, 11-16-2021; Ord.
No. 3333 N.S., § 5, 12-6-2022)
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