What is an Accessory Dwelling Unit (ADU)?
An Accessory Dwelling Unit (ADU) is an attached or detached residential unit that provides complete independent living facilities, including a bedroom, kitchen, and bathroom. A Junior Accessory Dwelling Unit can be no larger than 500 square feet and is contained entirely within an existing or proposed single-family home or accessory structure. A junior ADU may include its own bathroom, or share with the existing home.
In the single-family residential zoning districts (A, R-1, or HR zoning districts), one ADU and one junior ADU are allowed on a lot that contains an existing or concurrently approved single-family home. In the multi-family residential zoning district (R-M zoning district), up to two detached ADUs may be allowed. In addition, for every four dwelling units in a multi-family dwelling, one ADU may be created within existing non-habitable space, including, but not limited to, storage rooms, boiler rooms, passageways, attics, basements, or garages.
ADUs may be rented, but cannot be sold separately from the main home. For ADU applications received after January 1, 2025, the owner of the lot must also live on the lot.
Permitting Process
The construction of an ADU or junior ADU are processed without a public hearing, subject to approval of a building permit. However, ADUs that result in the following will require Design Review prior to building permit submittal:
- A new multi-story main structure or multi-story accessory structure
- The conversion of a single-story structure to a multi-story structure
- A new structure over 18 feet in height or an existing structure that would exceed 18 feet in height as a result of the proposed construction
Legalization of Existing ADUs
ADUs and junior ADUs that were established within a permitted structure between August 18, 1984 and February 19, 2003 may apply for legalization with reduced development standards.
Summary of ADU Development Standards
Item | Requirement |
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| Access | - The ADU and main home must use the same driveway to access the street
- If the ADU is attached to the main home, both the ADU and the main home may be served by a common entrance, however a separate exterior entrance to the ADU must be located on the side or at the rear of the main home
- No interior access is allowed between an accessory structure and an ADU
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| Appearance | - All new construction for an ADU must match the existing or concurrently approved main home in color, material, and architectural design
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| Bedrooms | - An ADU can have a maximum of 2 bedrooms
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| Conversion of an Existing Accessory Structure | - The interior space of an existing accessory structure that is converted to an ADU may be expanded by no more than 150 square feet beyond the physical dimensions of the existing structure for the sole purpose of accommodating ingress and egress
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| Fire Sprinklers | - An ADU is not required to provide fire sprinklers unless fire sprinklers are required for the main home. To determine if an ADU requires fire sprinklers, send an inquiry to prevention@sccfd.org
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Floor Area and Site Coverage | - An attached ADU cannot exceed 50% of the existing or concurrently approved living area of the main home, with a maximum size of 1,200 square feet, not including the garage
- A detached ADU, which is not located within a side or rear setback area, cannot exceed 1,200 square feet of living area, not including the garage
- If an ADU has a basement or an attic, that area is included as part of the total maximum floor area allowed
- Both the ADU and the main home count toward the total floor area and site coverage limits. However, an 800 square foot ADU shall be permitted in excess of the maximum allowable floor area and site coverage requirements
- For lots that are at least 10,000 net square feet in size, a one-time 10% increase in site coverage and allowable floor area may be granted by the Community Development Director if the new ADU is deed restricted so it may only be rented to below market rate households
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| Height | - A detached ADU located partially or entirely within a side or rear setback area cannot exceed 16 feet in height
- A detached or attached ADU located outside setback areas cannot exceed 26 feet in height
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| Parking | - One off-street parking space is required, in addition to the parking spaces required for the main home
- The parking requirement may be waived for junior ADUs and for ADUs that are part of the proposed or existing main home or accessory structure
- When a garage or carport is demolished for the construction of an ADU, any lost off-street parking spaces required for the main home are not required to be replaced
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| Setbacks | - An attached ADU must comply with the setbacks required for the main home
- A one-bedroom detached ADU that is 850 square feet or less, or a two-bedroom ADU that is 1,000 square feet or less may have rear and side setbacks of 4 feet
- Setbacks of less than 4 feet are allowed if the ADU is constructed in the same location and to the same dimensions as an existing legal structure that is demolished for the purpose of constructing the ADU
- A setback of 5 feet from the side and rear lot lines is allowed for an ADU constructed above an existing garage with legal non-conforming setbacks
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