Number of ADUs Allowed in the City of Los Simi Valley
- Maximum size: 1,200 sq ft (detached or attached, or 50% of the size of the main dwelling)
- Side/rear setbacks: 4 feet
- Two story: Yes, for both attached and detached ADUs
- Building separation: 6 feet
- Soils Report: Possibly, especially in areas with grading or on hillsides
- Building Verification Survey: Yes
- Coastal permit (in some areas): N/A
- Stormwater Mitigation: Yes
Number of ADUs Allowed in Simi Valley
You are allowed to put one attached or detached ADU on single-family property in Simi Valley, as well as one JADU.
Multifamily property owners in Simi Valley may convert existing uninhabitable space into at least one attached ADU, and additional ADUs not to exceed a maximum number equal to 25% of the existing units. Ergo:
- From 2 to 7 units, you could convert existing uninhabitable space into one ADU
- From 8 to 11 units up to 2 ADUs
- From 12 to 15 units up to 3 ADUs
- And so on.
Up to 8 detached ADUs can be built on multifamily property, as long as the number of detached ADUs does not exceed the current number of units on the property.
ADU Simi Valley – Size & Building Constraints
A detached ADU can be up to 1,200 square feet in Simi Valley.
An attached ADU in Simi Valley can be up to 1,200 square feet, or 50% of the square footage of the primary dwelling unit, whichever is smaller.
A detached ADU can be built to a maximum height of 16 feet in Simi Valley. An attached ADU can be built to a maximum height of 25 feet as long as it doesn’t exceed the height of the primary dwelling unit.
As long as the height requirement is adhered to, nothing specifically prohibits you from building a 2-story ADU. 16 feet is probably too short; an 18-foot structure is about the minimum for two stories.
Since only one ADU is allowed on single-family property in Simi Valley, you cannot have two ADUs stacked one on top of another with one on each story. Stacked ADUs may be permitted on multifamily property if height restrictions and other conditions are adhered to.
Since only one ADU is allowed on single-family property in Simi Valley, you cannot have two ADUs attached to one another in one structure. Detached structures containing multiple ADUs may be permitted on multifamily property.
No, a JADU is defined as an ADU converted from existing space within the main structure of the primary dwelling unit. As such, it cannot be attached to an ADU.
Generally roof decks would be permitted on an ADU, but must meet the height restrictions for the zone. Roof decks cannot encroach into the required setbacks. As a rule of thumb, railings and access staircases above 42″ need to be included in height calculations.
An ADU must match or harmonize with the exterior of the main dwelling unit, including color palette, roof pitch, architectural style, and other aesthetic characteristics (similar to a garage conversion).
ADU Setbacks in Simi Valley
ADUs behind the primary dwelling unit in Simi Valley require a minimum of 4-foot side and rear setbacks.
A detached ADU must be at least 6 feet from existing structures.
ADUs are not permitted in the front yard of residential property in Simi Valley.
ADU Setbacks in Simi Valley
No, you can apply for a permit and submit plans online using Simi Valley’s customer self-service online portal, accessiblehere.
Simi Valley may require a soils report for ADU permitting to make sure the soil can support the new structure, especially if the ADU construction will be located on a hillside, an area with significant grading, or if there are special foundation requirements.
Sufficient green space and permeable surface must be maintained on the property. City regulations do not specify specific percentages and must be approved on a case-by-case basis in the planning stage.
Plans are submitted to the Simi Valley Building and Safety Division, which checks the plans for compliance with building codes, safety codes, and structural integrity. Turnaround times can vary, but the process takes an average of 20-25 business days.
Parking for Simi Valley ADU
One new parking spot is typically required to be added to the lot per new ADU. However, exemptions may apply if:
- The ADU was built into an existing structure.
- The property is located within a historic district.
- The property is located within ½ mile walking distance of a public transportation stop.
- The property is located within one block of an established vehicle share stop.
- Off-street parking permits are required but not offered to ADU occupants.
If a parking space must be added, it can be included on the driveway or any setback areas, and it may be configured as tandem parking.
Additional Requirements in Simi Valley
Per Title 24 of the California Energy Code, solar panels of appropriate size and capacity are mandatory on new-construction ADUs. ADUs built from converted existing structures are exempt, as may be ADUs located under significant shading. Smaller ADUs may be subject to reduced or modified solar panel requirements.
An ADU is not required to have a separate water or electrical meter. You can opt for the ADU to share service with the main dwelling unit. However, you can request separate water or electrical meters from the City of Simi Valley.
An ADU doesn’t necessarily get its own address, but a separate address can be applied for and may be mandated if determined by the city to be necessary for public safety reasons.
Low Impact Development (LID) is an approach to land development or redevelopment that seeks to preserve and conserve onsite water quality and natural features, with minimal detrimental effect to local waterways and ecosystems. The City of Simi Valley may require LID fees for larger ADUs.
You can, but California State Law requires that dwelling units can only be used as short-term rentals or Airbnbs for terms of 30 days or longer.
Per the Costa-Hawkins Act of 1995, Simi Valley does not impose rent control on dwellings constructed after February 1, 1995. This means most new-build ADUs are exempt. However, if the primary dwelling unit is subject to rent control, it might apply to the ADU as well.
While encouraging the use of electric appliances for efficiency and sustainability, Simi Valley does not prohibit gas appliances in new ADUs as long as all relevant installation and safety standards are met.
In Simi Valley you are only required to install sprinklers in a new ADU if the primary dwelling unit has them as well. You may also be required to install them if the ADU is located within a special fire hazard zone.
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