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Simi Valley ADUs

Everything about building Accessory Dwelling Units in Simi Valley, CA

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574 sqft
Bell Canyon

749 sf
1 Bed
The city government of Simi Valley has updated its local zoning codes to comply with the State ADU mandate.
The California Building Code (CBC) 2019 is adopted.

Last Updated 09/19/21


City Hint: The City of Simi Valley permitted a total of 52 ADU projects in the past year of 2020.

Number of ADUs allowed:

One ADU may be allowed per single family dwelling. You can combine an ADU on the same lot as a JADU if the ADU is detached and a maximum of 800 square feet in size.

One JADU may be allowed per existing single-family residence. You can combine a JADU with an ADU as long as the ADU is detached and a maximum of 800 square feet in size.

Types of ADUs allowed:

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

Lot size:

Accessory Dwelling Unit projects on single family or multi-family residential lots will not be subject to the minimum lot size of the underlying local zoning code or by special ordinance. ~ According To AB68

ADU size:

Attached ADUs:
- 800 square feet or 50% of the square footage of the single family residence (net square footage if a portion of an existing home is converted) up to a maximum of 1,000 square feet, whichever is larger.

Detached ADUs:
- 800 square feet if combined with a JADU on a single lot.
- 1,000 square feet on lots up to 8,000 square feet.
- 1,200 square feet on lots over 8,000 square feet.

JADU: 500 square feet maximum.
Minimum Size Allowed: 220 square feet.


ADU Side and Rear Setbacks:
A minimum of four (4) feet is required for each. Note that setbacks less than five (5) feet will be subject to additional Building Code requirements for fire rating of exterior walls which will increase the costs of construction.

Other Setbacks: 20 feet front yard setback.
Six (6) foot separation from any existing structures.

If you propose an addition to create your JADU, the setbacks will be the same as for a single-family residence:
- Five (5) foot for side setback required for a one-story structure
- 20 foot rear yard setback
- 20 foot front yard setback


Parking Requirement: If you are proposing a Studio Unit, within ½ mile of a public transit stop, converting a portion of your home or converting a garage to an ADU, you will most likely not need to provide an additional parking space.

Parking Location: If you require additional parking, this may be uncovered or tandem parking on the driveway that meets the City’s requirements as laid out in the Simi Valley Development Code Section 9-34.040.

JADU - No additional parking requirements.

Fire Safety:

Accessory dwelling units shall not be required to provide fire sprinklers if they are not required for the primary dwelling unless otherwise required by the Fire Code.

Shape, materials and style:

Design Standards: The materials and colors of exterior walls, roof, eaves, windows, and doors of an ADU must match those of the primary dwelling. The roof slope of an ADU must match the dominant roof slope of the primary dwelling. The dominant roof slope is the slope shared by the largest portion of the roof. This will need to be shown on your final plans.


Maximum Height: 18 feet and one story (a story is defined as the first sixteen vertical feet of the wall plane as measured from the finished floor to the top of the roof surface. Vertical height in excess of sixteen feet along the wall plane will be counted as a second floor).

Design review:

State Standards don't require any additional design review.

Number of Bedrooms:

Not specified by State Standards.


Owner Occupancy Requirement: Owner-occupancy is not required for the accessory dwelling unit or main residence.

Owner-occupancy is required for either the JADU or the main residence.

Utility connections:

A junior accessory dwelling unit may include separate sanitation facilities or may share sanitation facilities with the existing structure, must include one existing bedroom of the existing single-family dwelling, and have an internal connection to the existing single-family dwelling.


Passageway. A pathway that is unobstructed clear to the sky and extends from a street to one entrance of the accessory dwelling unit.

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. ***

An existing single-family dwelling and zone OS, RE, RVL, RL, RM, [/Rmod/], RH, and RVH

Open Space:

Attached ADUs: Not Required

Detached ADUs up to 800 square feet:
Not Required

Detached ADUs over 800 square feet
- The cumulative yard coverage of all accessory structures cannot be more than 40% of any yard.
- 50% of rear yard width needs to be kept open

Residential Building Code:

The California Building Code (CBC) 2019 is adopted.

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