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Aliso Viejo ADUs

Everything about building Accessory Dwelling Units in Aliso Viejo, CA

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400 sqft

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1 Bed

Aliso Viejo ADU Guidelines Last Updated 08/14/21

The city government of Aliso Viejo has updated its local zoning codes to comply with the State ADU mandate.
The California Building Code (CBC) 2019 is adopted.

Number of ADUs allowed:

Under state law, each single-family home may now build at least one ADU. Owner occupied single-family lots may build one ADU and one Junior Accessory Dwelling Unit (JADU). Multi-family lots, per every four existing residential units, may build one ADU, so long as the existing units were legally established.

Types of ADUs allowed:

Detached ADU, Attached ADU, Junior ADU are approved. Accessory Dwelling Unit (ADU)s may be new construction or converted from existing space. Junior Accessort Dwelling Unit (JADU)s must be converted from existing space.

Lot size:

Residential lots will not be subject to any minimum lot size for ADUs by ordinance or of the underlying zoning district. ~ Updated: State Law AB-68

ADU size:

Single-family and multi-family Properties will be approved to construct up to 850 sq. ft. for a one bed ADU or up to 1,000 sq. ft. for a two bed ADU, regardless of the underlying zoning standards of the property. A Junior Accessory Dwelling Unit up to 500 sq. ft. is approved. The minimum size of any living unit (including Accessory Dwelling Units and Junior Accessory Dwelling Units) is 150 sq. ft. according to California Residential Code. ~ AB-68


Setbacks for a detached new construction ADU shall be no more than 4 ft from the rear and side lot lines. No setbacks shall be required for ADUs and JADUs converted from legally eastablished existing space. Attached new construction ADUs and conversions from existing space to be expanded must comply with the setbacks of the underlying zone. ~ AB68 & AB881 Update


Replacement parking shall not apply to properties which convert an existing garage to an Accessory Dwelling Unit or Junior ADU. ~ AB68

Fire Safety:

Fire sprinklers are only required in the converted ADU if they are required in the primary dwelling. The site and REAR setbacks must be sufficient for fire safety.

Shape, materials and style:

The design, building and roofing materials, colors, and overall appearance of the accessory dwelling unit must be substantially the same as those of the principal unit, while conforming to the current building code. For example, the roof pitch, roof and exterior-wall materials and colors, and window and door styles and colors must be the same. The ADU must have independent exterior access from the existing primary dwelling, and the outside door may not locate on the primary elevation of the primary dwelling unit or anywhere else that is visible from the street.


The maximum height shall be fifteen feet. The height shall not exceed the height limit applied to a primary unit in the underlying zoning district.

Design review:

The planning director shall approve an application for an accessory dwelling unit , without public notice or a public hearing, within 120 days if the director finds and determines that the proposed unit conforms to the provisions of this section.

Number of Bedrooms:

Not specified by State Standards.


Between between 2020 and 2025, owner occupancy requirements will not apply to new ADUs. (applicable to new construction and conversion units) ~ SB13 Update

Utility connections:

Local health officer approval where a private sewage disposal system is being used, if required. (State requirements)

Historic Requirements:

The accessory dwelling unit is located within an official architecturally and historically significant district, additional review may be required.


The ADU shall have exterior access separate from that of the existing primary residence.

Allowed Zones:

*** Beginning in 2020, according to state law, all residential zoning districts, including single-family and multi-family, are allowed to build Accessory Dwelling Units. ***

For residential zoning designations (RL, RM, RH and RVH) ADUs are permitted pursuant to the required standards outlined in the Section 15.14.080.

Residential Building Code:

The California Building Code (CBC) 2019 is adopted.

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