San Diego County, CA - ADU Regulations

Rules and regulations for building an ADU.

ADU info for

San Diego County

  • ADU allowed?
    YES
  • Number of ADUs allowed?
    1 ADU and 1 JADU
  • Max ADU Size
    1,200 SQFT
  • Eligibility
    most single-family and multi-family zoned properties
  • Setbacks
    minimum 4-foot setback from the side and rear property lines
  • Parking Requirements
    limited requirements, especially if the property is near public transit
  • ADU allowed?
    YES
  • Number of ADUs allowed?
    1 ADU
  • Max ADU Size
    750 SQFT
  • Eligibility
    R-5, R-4, and R-4A-zoned lots
  • Setbacks
    minimum 7-foot setback from the side and 15-foot rear property lines
  • Parking Requirements
    limited requirements, especially if the property is near public transit
  • ADU allowed?
    YES
  • Number of ADUs allowed?
    2 ADU
  • Max ADU Size
    1,000 SQFT (typically)
  • Eligibility
    Most residential zones
  • Owner Occupancy
    not required*
  • ADU allowed?
    YES
  • Number of ADUs allowed?
    1 ADU
  • Max ADU Size
    800-900 SQFT (typically)
  • Eligibility
    Varies but typically cities with population over 2,500; Counties over 15,000
  • Owner Occupancy
    Not required for most cases
  • Key Note
    Urban Growth Boundaries (UGBs) affect development location
  • ADU allowed?
    YES
  • Number of ADUs allowed?
    1 ADU
  • Max ADU Size
    Read details below.
  • Eligibility
    Read details below.
  • Setbacks
    Read details below.
  • Parking Requirements
    limited requirements, especially if the property is near public transit

Understand ADU zoning rules for

San Diego County

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Different types of ADUs allowed in

San Diego County

Though backyard homes are typically the most familiar, ADU structures come in various types. The illustration below shows the four primary types of ADU structures.

ADUs can be built using a variety of construction methods, including pre-fabricated, modular, shed, container, panelized (in pieces), and stick-built. Each construction method has its own advantages and disadvantages in terms of cost, time, and customization.

detached adu
Detached ADU
garage conversion adu
Garage Conversion ADU
addition / attached adu
Addition / Attached ADU
detached adu
Detached ADU
garage conversion adu
Garage Conversion ADU
addition / attached adu
Addition / Attached ADU
detached adu
Detached ADU
garage conversion adu
Garage Conversion ADU
addition / attached adu
Addition / Attached ADU
detached adu
Detached ADU
garage conversion adu
Garage Conversion ADU
addition / attached adu
Addition / Attached ADU

ADU regulations for

San Diego County

In a proactive effort to combat the ongoing housing crisis, the State of California has adopted specific regulations to promote the construction and utilization of Accessory Dwelling Units (ADUs). Here's an expanded and comprehensive breakdown of the key points:

1. Purpose and Prominence: California recognizes the potential of ADUs in providing affordable housing options. Given the state's dense urban centers and escalating property prices, ADUs present a viable solution to address the growing demand for residential spaces.

2. Eligibility for Establishment: Both single-family homes and multifamily properties can host an ADU.

3. Size Considerations: For detached ADUs, the maximum allowable size is up to 1,200 square feet.
The actual size of an ADU might vary depending on specific factors such as the total lot area and the size of the primary dwelling on the property.

4. Parking Norms: The state mandates limited parking requirements for ADUs.
If an ADU is situated near public transit, these parking stipulations may be even less stringent, facilitating easy construction and usage.

5. Owner-Occupancy: Historically, some jurisdictions required the property owner to live in either the primary home or the ADU. However, for ADUs permitted between 2020 and 2025, the state does not enforce such owner-occupancy requirements, allowing for greater flexibility in usage.

6. Setback Rules: For detached ADUs, there's a minimum setback requirement of 4 feet from both the rear and side yard boundaries.

7. Approval Process: Cities across the state are obligated to approve compliant ADU applications within a span of 60 days. This streamlined process ensures quick turnarounds and encourages homeowners to consider ADU development.

8. Fee Structure: To further incentivize ADU establishment, the state has reduced or completely waived fees for ADUs that are less than 750 square feet. This can translate to significant savings for property owners.

9. Rental Conditions: If an ADU meets the stipulated requirements laid out by the city, it must be available for rental. This regulation ensures that ADUs actively contribute to alleviating housing shortages.

10. Local Jurisdictional Variances: While the above guidelines provide a general framework, it's crucial to note that local jurisdictions might have their unique sets of regulations and requirements. Property owners should consult their respective city or county planning departments to get precise and localized information.

In conclusion, as California grapples with housing challenges, ADUs offer a promising avenue to augment living spaces without the need for expansive new developments. These guidelines, though comprehensive, serve as a starting point, and it's always recommended to liaise with local experts for tailored advice.

State laws (RCW 36.70A.680 and 36.70A.681) mandate that all local governments under the Growth Management Act (GMA), irrespective of size and including both cities and counties within unincorporated urban growth areas, update their regulations to align with specific criteria within six months following their scheduled update. The key directives include:

  1. ADUs per Lot: Urban areas within the GMA must allow at least two ADUs on any lot that qualifies by size, in addition to the main residence. These ADUs can be attached, detached, or a mix, and converting structures like garages into ADUs must be permitted.
  2. Size Requirements: ADUs cannot be restricted to under 1,000 square feet.
  3. Design and Location Standards: Restrictions on setbacks, lot coverage, tree preservation, or entrance placements cannot be stricter than those for the main home.
  4. Street Upgrades: ADUs cannot be subjected to demands for street improvements as a permit condition.
  5. Owner Occupancy: Requirements for the homeowner to live on-site are prohibited for both the main and accessory units.
  6. Condominium Sales: It’s not allowed to block the sale of a condominium developed as an ADU on the basis that it’s an ADU.
  7. Design Review: ADUs cannot face stricter aesthetic or design criteria than the primary residence.
  8. Parking: Parking requirements are limited, with specific conditions for smaller lots and exemptions for ADUs near major transit hubs.
  9. Impact Fees: Charges for ADUs are capped at 50% of those for the main house.
  10. Common Interest Communities: New developments with homeowners associations are barred from implementing rules against ADU construction. However, existing regulations can remain.

These regulations aim to encourage the development of ADUs, offering more housing options within urban growth areas.

Since July 1, 2018, most Oregon cities and counties allow homeowners to build Accessory Dwelling Units (ADUs) on residential properties. However, local rules on ADU size, placement, and design must be followed. Each area has its own rules for:

  1. How big the ADU can be;
  2. Where it can be located; and
  3. If it needs to look like the main house.

Local governments also have different processes for giving permits and may charge fees for building an ADU. These fees, including impact fees or system development charges, can vary a lot. Some places might not charge these fees at all, while others could charge $15,000 or more for each ADU.

In Oregon, the rules for creating Accessory Dwelling Units (ADUs) set standards to boost housing while keeping communities looking good. Understanding Oregon's ADU laws is crucial for compliance and making the most of ADU benefits. Cities must have over 2,500 people, and counties over 15,000, to fall under the ADU mandate. This supports urban housing needs. Urban Growth Boundaries (UGBs) define where ADUs can be built, promoting smart growth and land use without harming Oregon's landscapes.

Oregon's ADU laws aim to increase affordable housing. They require local governments to process ADU applications efficiently, especially in urban areas. State laws stop local rules from demanding owners live in ADUs or provide extra parking, except for vacation rentals. Setback requirements ensure ADUs are well-placed, respecting privacy and the environment. Oregon encourages updating local ADU rules to match state standards, making it easier to build ADUs and help with housing shortages.

Design and siting rules for Oregon ADUs ensure they fit well with urban settings and offer design flexibility. Oregon prefers less restrictive rules for ADUs compared to other buildings, aiming to increase housing options responsibly. The state simplifies ADU regulations, replacing complex zoning laws with clearer, state-wide standards. This helps reduce red tape and encourage ADU construction.

Oregon's approach to ADUs, including size restrictions and utility connection guidelines, is designed to integrate ADUs smoothly into neighborhoods, addressing housing needs. ADUs can't be too large compared to the main house, and shared utility connections are encouraged to keep costs down. This effort shows Oregon's commitment to innovative, affordable housing solutions.

  • Oregon ADU laws establish criteria to support housing while maintaining community aesthetics.
  • Cities over 2,500 people, and counties over 15,000, need to allow ADU construction per state mandates.
  • Urban Growth Boundaries (UGBs) are key to ADU development, limiting expansion within set geographic areas.
  • The state prohibits local ordinances from requiring owner occupancy or off-street parking for ADUs, except for vacation rentals.
  • Oregon mandates setback requirements for ADUs to ensure privacy and environmental standards.
  • Local governments in Oregon must update regulations to align with state ADU codes, promoting consistent and simplified ADU development.
  • Oregon ADU laws facilitate affordable housing by removing barriers to ADU construction and simplifying the application process.
  • Design standards for ADUs in Oregon are clear and objective, not requiring ADUs to mimic the primary residence's architecture.
  • Oregon's policies allow ADUs more flexibility in development compared to other accessory structures, avoiding strict lot size or coverage constraints.
  • ADUs in Oregon are subject to size limitations, generally not exceeding 75-85% of the primary dwelling's floor area, with specific square footage caps.
  • The state encourages the use of shared utility connections for ADUs to lower construction and development costs.
  • Oregon's comprehensive ADU regulations aim to expand housing options, reduce bureaucracy, and accommodate the state's diverse housing needs.
  • As per California State Law, residential properties can have an Accessory Dwelling Unit (ADU) and/or a Junior Accessory Dwelling Unit (JADU). These living spaces provide separate facilities for one or more individuals and can be added to existing or proposed single-family dwellings (SFDs). A JADU is a self-contained living area within the SFD, with a maximum size of 500 square feet, complete with its own exterior and interior access, and a full bathroom. It is advisable to promptly contact the relevant Fire Department to ensure ADU compliance with fire setbacks and determine if fire sprinklers are required.

    For lots with existing or proposed SFDs (single family dwelling) in residential or mixed-use zones, one ADU and one JADU may be allowed if the following conditions are met:

    • The ADU must be attached to the existing SFD or detached but on the same legal lot.
    • The ADU can be rented out but not sold separately from the primary residence.
    • The lot must not already have a guest living quarters, accessory living quarters, or accessory apartment. However, it may be possible to convert an existing guest living quarters, accessory living quarters, or accessory apartment into an ADU with a building permit.
    • The attached ADU must not exceed 50% of the SFD's floor area, up to a maximum of 1,200 square feet. The detached ADU must not exceed 1,200 square feet, regardless of the size of the existing SFD.
    • Applicants must provide mathematical calculations of the "floor area" for both units on the plot plans, based on the exterior dimensions of the outside walls.
    • The proposed garage attached to a detached ADU must not exceed the allowable combined square footages specified in Section 6156.g unless authorized by an approved Administrative Permit.
    • No other rooms, additions, or uses can be attached to the ADU, except for a garage, unless authorized by an approved Administrative Permit.
    • An ADU may potentially be attached to an existing and permitted barn, shed, workshop, or similar structure, as long as it is placed within the existing and permitted accessory structure and does not have internal communication with the remaining portions of the structure.
    • Setbacks are not required if an existing and permitted accessory structure, or a portion thereof, is converted into an ADU, except for fire safety.
    • When converting an existing detached or attached accessory structure into an ADU, it is important to ensure that any new addition for the ADU complies with the specified setbacks.
    • A detached ADU typically has a maximum height of 24 feet, with exceptions for multifamily complexes.
    • For an ADU constructed above a permitted detached accessory structure, it is necessary to maintain a setback of at least 4' from the side and rear lot lines. These setbacks specifically apply to the additional space above the accessory structure, allowing the ADU to extend beyond its walls.
    • All newly constructed ADUs must adhere to the required front and exterior side yard setbacks, as well as a minimum side and rear setback of 4' (excluding any required fire setbacks).
    • Any attached garage, carport, patio, or other accessory structure to an ADU must comply with the regular setback and height regulations outlined in the Zoning Ordinance.
    • If an ADU is attached to the primary residence, it should conform to the required main building setbacks.
    • It is important to note that an ADU must provide at least one parking space, which can be located within the setbacks or in an existing tandem parking driveway. There is no need to replace parking spaces when a garage, carport, or covered parking structure is demolished or converted into an ADU.
    • However, there are specific instances where a parking space is not required for an ADU. Firstly, if the ADU is situated within half a mile of public transit. Secondly, if the ADU is located within an architecturally and historically significant historic district.
    • It is prohibited to separately sell or own an ADU, unless the lot is subdivided to create separate lots for each dwelling.
    • Additionally, it is important to remember that an ADU cannot be used or rented for less than 30 days.
    • In cases where a property has an existing non-conforming single-family residence and is in a zone that does not allow residential use, there may be potential allowance for an ADU and/or JADU.
    • However, properties with multiple existing non-conforming single-family residences in a residential zone that only permits single-family residences are not permitted to have an ADU or JADU.

    Requirements for Junior Accessory Dwelling Units (JADU):

    • One Junior Accessory Dwelling Unit (JADU) and one detached Accessory Dwelling Unit (ADU) may be permitted on lots within a residential or mixed-use zone that already have or propose a Single Family Dwelling (SFD).
    • The JADU should not exceed a total area of 500 square feet.
    • The JADU must maintain an interior connection to the main living area, while also having a separate exterior entry.
    • The JADU should include an efficiency kitchen, consisting of a cooking facility with appliances, and a food preparation counter with storage cabinets proportionate to the size of the unit.
    • No additional parking is required for the JADU.
    • The JADU cannot be rented for less than a 30-day period.
    • While the JADU may be rented out, it cannot be sold separately from the primary residence. The owner must live in one of the two units.
    • New proposed ADUs on lots with an existing and permitted SFD may be eligible for the County Fee Waiver Program until January 2024. For more information, please visit the County Fee Waiver Program. Note that JADUs are not eligible for the Fee Waiver Program.

    ADU Regulations for Multifamily Complexes

    • Multiple ADU's may be permitted within portions of an existing multifamily complex within a residential or mixed-use zone if certain requirements are met:
    • Only structures/rooms within the existing multifamily complex that are not used as livable space can potentially be converted into multiple ADU's, up to 25% of the existing multifamily dwelling units.
    • Up to two detached ADU's may be permitted per lot that has an existing multifamily complex if certain requirements are met:
    • The detached ADU's are limited to a height of 16 feet and 4' rear yard and side setbacks.
    • The addition of two detached ADU's is not subject to any nonconforming regulations.
    • Multiple ADU's for multifamily complexes do not qualify for the County Fee Waiver Program.
    • Regarding the ADU regulations, any structure designed for human habitation that is divided into two or more independent living quarters on a single lot is considered a multifamily complex.

    As per California State Law, residential properties can have an Accessory Dwelling Unit (ADU) and/or a Junior Accessory Dwelling Unit (JADU). These living spaces provide separate facilities for one or more individuals and can be added to existing or proposed single-family dwellings (SFDs). A JADU is a self-contained living area within the SFD, with a maximum size of 500 square feet, complete with its own exterior and interior access, and a full bathroom. It is advisable to promptly contact the relevant Fire Department to ensure ADU compliance with fire setbacks and determine if fire sprinklers are required.

    For lots with existing or proposed SFDs (single family dwelling) in residential or mixed-use zones, one ADU and one JADU may be allowed if the following conditions are met:

    • The ADU must be attached to the existing SFD or detached but on the same legal lot.
    • The ADU can be rented out but not sold separately from the primary residence.
    • The lot must not already have a guest living quarters, accessory living quarters, or accessory apartment. However, it may be possible to convert an existing guest living quarters, accessory living quarters, or accessory apartment into an ADU with a building permit.
    • The attached ADU must not exceed 50% of the SFD's floor area, up to a maximum of 1,200 square feet. The detached ADU must not exceed 1,200 square feet, regardless of the size of the existing SFD.
    • Applicants must provide mathematical calculations of the "floor area" for both units on the plot plans, based on the exterior dimensions of the outside walls.
    • The proposed garage attached to a detached ADU must not exceed the allowable combined square footages specified in Section 6156.g unless authorized by an approved Administrative Permit.
    • No other rooms, additions, or uses can be attached to the ADU, except for a garage, unless authorized by an approved Administrative Permit.
    • An ADU may potentially be attached to an existing and permitted barn, shed, workshop, or similar structure, as long as it is placed within the existing and permitted accessory structure and does not have internal communication with the remaining portions of the structure.
    • Setbacks are not required if an existing and permitted accessory structure, or a portion thereof, is converted into an ADU, except for fire safety.
    • When converting an existing detached or attached accessory structure into an ADU, it is important to ensure that any new addition for the ADU complies with the specified setbacks.
    • A detached ADU typically has a maximum height of 24 feet, with exceptions for multifamily complexes.
    • For an ADU constructed above a permitted detached accessory structure, it is necessary to maintain a setback of at least 4' from the side and rear lot lines. These setbacks specifically apply to the additional space above the accessory structure, allowing the ADU to extend beyond its walls.
    • All newly constructed ADUs must adhere to the required front and exterior side yard setbacks, as well as a minimum side and rear setback of 4' (excluding any required fire setbacks).
    • Any attached garage, carport, patio, or other accessory structure to an ADU must comply with the regular setback and height regulations outlined in the Zoning Ordinance.
    • If an ADU is attached to the primary residence, it should conform to the required main building setbacks.
    • It is important to note that an ADU must provide at least one parking space, which can be located within the setbacks or in an existing tandem parking driveway. There is no need to replace parking spaces when a garage, carport, or covered parking structure is demolished or converted into an ADU.
    • However, there are specific instances where a parking space is not required for an ADU. Firstly, if the ADU is situated within half a mile of public transit. Secondly, if the ADU is located within an architecturally and historically significant historic district.
    • It is prohibited to separately sell or own an ADU, unless the lot is subdivided to create separate lots for each dwelling.
    • Additionally, it is important to remember that an ADU cannot be used or rented for less than 30 days.
    • In cases where a property has an existing non-conforming single-family residence and is in a zone that does not allow residential use, there may be potential allowance for an ADU and/or JADU.
    • However, properties with multiple existing non-conforming single-family residences in a residential zone that only permits single-family residences are not permitted to have an ADU or JADU.

    Requirements for Junior Accessory Dwelling Units (JADU):

    • One Junior Accessory Dwelling Unit (JADU) and one detached Accessory Dwelling Unit (ADU) may be permitted on lots within a residential or mixed-use zone that already have or propose a Single Family Dwelling (SFD).
    • The JADU should not exceed a total area of 500 square feet.
    • The JADU must maintain an interior connection to the main living area, while also having a separate exterior entry.
    • The JADU should include an efficiency kitchen, consisting of a cooking facility with appliances, and a food preparation counter with storage cabinets proportionate to the size of the unit.
    • No additional parking is required for the JADU.
    • The JADU cannot be rented for less than a 30-day period.
    • While the JADU may be rented out, it cannot be sold separately from the primary residence. The owner must live in one of the two units.
    • New proposed ADUs on lots with an existing and permitted SFD may be eligible for the County Fee Waiver Program until January 2024. For more information, please visit the County Fee Waiver Program. Note that JADUs are not eligible for the Fee Waiver Program.

    ADU Regulations for Multifamily Complexes

    • Multiple ADU's may be permitted within portions of an existing multifamily complex within a residential or mixed-use zone if certain requirements are met:
    • Only structures/rooms within the existing multifamily complex that are not used as livable space can potentially be converted into multiple ADU's, up to 25% of the existing multifamily dwelling units.
    • Up to two detached ADU's may be permitted per lot that has an existing multifamily complex if certain requirements are met:
    • The detached ADU's are limited to a height of 16 feet and 4' rear yard and side setbacks.
    • The addition of two detached ADU's is not subject to any nonconforming regulations.
    • Multiple ADU's for multifamily complexes do not qualify for the County Fee Waiver Program.
    • Regarding the ADU regulations, any structure designed for human habitation that is divided into two or more independent living quarters on a single lot is considered a multifamily complex.

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    City Snapshot

    San Diego County

    Population
    76000
    Median Household Income

    San Diego is located in Southern California and is renowned for its cultural heritage and beautiful landscapes. It provides residents with both urban amenities and suburban comfort.

    Browse ADU regulations for other cities

    32.7157

    -117.1611

    Frequently Asked Questions

    What is an ADU and how can you help me build one?

    An ADU, or Accessory Dwelling Unit, is also known as a tiny home, granny flat, in-law unit, or garage apartment. We help homeowners by providing expert guidance and tools to navigate the process of building an ADU, from zoning and permitting, to design and size considerations, to cost estimation, and through the construction process itself.

    How can I determine if my local area allows for ADU construction?

    Our services include assistance with zoning and permitting. We help you identify your property's specific zoning requirements and the necessary permits for ADU construction, ensuring your project stays compliant with local regulations.

    What does the construction process for building an ADU look like?

    We offer information and resources on the construction process, timelines, and best practices for building an ADU. Additionally, we have a network of trusted builders you can partner with to ensure a seamless, efficient, and high-quality build for your ADU.

    What is included in your feasibility report for building an ADU?

    With the Gather Feasibility Report, you can confidently embark on your ADU journey, knowing you've got a solid foundation and a clear roadmap to success. Let us help you transform your space into a functional, comfortable, and profitable asset today.

    We
       
    1) Thoroughly analyze your property records for a tailored assessment,        
    2) Work with city and county authorities on your behalf for a hassle-free experience,        
    3) Secure a preliminary "pre-approval" from city/county for your peace of mind,        
    4) Deliver a comprehensive report document detailing your property's ADU possibilities.            

    Embark on your ADU adventure with Gather ADU, and make the most of your property's potential without the stress or hassle.

    Do I have to commit to the entire ADU construction project right away?

    No, it isn't required. GatherADU offers support at every step of the ADU process, allowing you to proceed without making an immediate full commitment. You have the flexibility to progress at your own pace and opt for pay-as-you-go.

    Where does GatherADU operate?

    GatherADU provides ADU design and planning services nationwide with focus on California, Washington, Oregon, and Georgia.