California ADU Requirements | The Complete Guide

With concern around California’s high cost of living, demand for accessory dwelling units (ADUs) is rising. These compact, affordable homes have added thousands of new housing units statewide since recent ADU reforms took effect. For property owners, ADUs offer multiple benefits: rental income, increased property value, and access to state and local grants to help with construction.

But if you’re thinking about adding an ADU, you’ve probably already encountered a maze of zoning codes, permit rules, and confusing legal language. In this article, we’ll break down the core legal requirements for building an ADU in California.

Read on to learn what qualifies as an ADU, how big it can be, what permits you’ll need, and what rules apply in major cities and counties across the state.

Are ADUs Legal in California?

Yes, California has introduced statewide legislation, outlining requirements for accessory dwelling units (ADUs) and junior accessory dwelling units (JADUs). This legislation requires that all areas permit ADUs, but still allows certain areas to impose their own sizing, placement, and design standards. You can learn more about state ADU requirements through the California Department of Housing & Community Development.

What Qualifies as an ADU in California?

California defines an accessory dwelling unit as an attached or detached residential dwelling unit that provides complete, independent living facilities for one or more persons, and is located on a lot with a proposed or existing primary residence. There are typically 3 forms of ADUs permitted:

1. Detached: A separate unit from the principal structure
2. Attached: A unit that is connected to the primary structure
3. Repurposed Existing Space: When a room inside a home or a garage is converted into an independent living unit

What is a JADU?

A junior accessory dwelling unit (JADU) is a unit no more than 500 square feet inside and contained entirely within a single-family residence. Unlike an ADU, a JADU is always part of the primary home. It cannot be detached and is limited to 500 square feet, whereas ADUs can be as large as 1,200 square feet, depending on local regulations.

How Many ADUs Are Allowed in California?

This largely depends on how your property is zoned, but in most cases, you can have two accessory dwelling units, one standard ADU, and a JADU. Be sure to check with your local zoning officials to determine exactly how many ADUs you can have on your property.

What Is the Minimum Size For An ADU in California?

ADUs must have at least 150 square feet of living area. However, minimum size requirements are often set by local officials, so check with them to ensure compliance.

How Big Can An ADU Be in California?

In most cases, an ADU cannot be larger than the main house. This applies to both total square footage and height. Common maximum sizes range from 850 to 1,200 square feet, depending on local regulations. Detached ADUs are typically limited to 16 feet in height, while attached ADUs can be up to 25 feet tall or match the height of the primary residence, whichever is lower.

JADUs follow different rules. They are usually limited to 500 square feet and must be attached to the main home, meaning they must also conform to its height limits.

To determine exactly how large your ADU can be, consult your local planning department or building officials.

Do You Need A Permit For An ADU in California?

Yes, permits are required to build an ADU in California. If you’re unsure which ones you’ll need, Golden State Buildings handles all necessary permit filings for constructing and adding an ADU to your property.

What Is The $40,000 Grant in California for ADUs?

The California Housing Finance Agency offers an ADU grant program that offers up to $40,000 to reimburse pre-development and non-recurring closing costs that come with constructing an ADU. Pre-development costs include site prep, architectural designs, permits, soil tests, impact fees, property surveys, and energy reports.

What Are The Requirements For ADUS In Each County in California?

To help you understand the requirements for building an ADU on your property in California, we’ve compiled a county-by-county guide and a chart linking to the appropriate government contacts. This will help ensure you can verify compliance with all applicable regulations.

Please note that Golden State Buildings does not serve every county in California. Our service area only extends to areas within 50 miles of our Sanger, CA, location. You can review our list of service areas to see if we build in your location. This resource is intended to help California residents better understand local ADU regulations, whether or not they’re located within our service area.

Keep in mind that cities and towns often have their own regulations. If you know your city enforces its own ADU standards, feel free to skip ahead to your specific area.

What are Alameda County’s ADU requirements?

Alameda County allows ADUs and JADUs, requiring that they either be attached to the principal structure, detached, or a converted interior space or carport. Additional requirements are as follows:

• Maximum Square Footage: 
  • 50% of the principal dwelling unit’s floor area or 1,200 sq. ft., whichever is less, but only if 1 ADU is proposed 
  •  800 sq. ft. if there is also a JADU being added to the property
  • 500 sq. ft. for a JADU
• Setbacks:
  • Side, street side, and rear: 4 feet for both attached and detached ADUs
  • Front: Must match the setback of the primary residence if the ADU is larger than 800 square feet
• Room Requirements:
  • If you only plan to have 0-1 bedroom, your ADU can only be a maximum of 850 square feet
  • For 2 or more bedrooms, your ADU can be a maximum of 1,200 square feet

Be sure to contact the Alameda County Planning Department to ensure your ADU plans comply with all applicable requirements.

What are Alpine County’s ADU requirements?

Alpine County permits both ADUs and JADUs and has the following requirements in place for them:

• Permits:
  • Building permit
  • Well permit or confirmation that the water supply can serve the ADU from the water provider
  • Verification from the Health Department that the wastewater system is sufficient for the ADU
• Setbacks:
  • Rear and side property lines: 4 feet
  • Front: Must follow Title 18 of the County Zoning Code
    • Cannot prevent an ADU of at least 800 square feet from being built on the property
• Maximum Square Footage:
  • For conversions of existing structures: none
  • For detached ADUs: 1,200 sq. ft.
  • For attached ADUs: 50% of the principal dwelling unit’s floor area or 800 square feet, whichever is more

If you have any questions about ADU requirements in the county, contact the Planning Department at 530-964-2140.

What are Amador County’s ADU requirements?

Amador County allows both JADUs and ADUs, requiring that:

• Number of Rooms:
  • At least one kitchen, bathroom, and sleeping area
  • May have multiple bedrooms depending on property size & location
• Minimum Square Footage: 150 sq. ft.
• RVs, Tiny Homes on Wheels (THOW), Yurts, and Storage Structures are not permitted as ADUs
• Types of ADUs:
  • Category 1: ADUs that are attached or detached and can be up to the same size as the main home.
    • If the main home is less than 1,000 square feet
      • Max Sq. Footage for one bedroom: 850
      • Max Sq. Footage for 2+ bedrooms: 1,000
    • Only one permitted per property
  • Category 2: Attached or detached ADU or JADU
    • Attached ADU Max Sq. Footage: 800 or 50% of the existing main home
    • Detached ADU Max Sq. Footage: 1,200
• ADU Height:
  • Category 1 ADUs
    • 30 feet for R1
    • 35 feet for R1A, R2, and R3
    • 45 feet for C1
  • Category 2 ADUs
    • Detached: 16 feet
    • The rest depend on the height of the existing structure
• Setbacks:
  • Depends on zoning for JADUs, internal, and conversion ADUs
  • Attached & detached ADUs: 4 feet for side and rear property lines, front setback requires on zoning

Given that many ADU requirements are based on your property’s zoning, be sure to check with the Amador County Planning Department to confirm zoning and ensure compliance with their requirements.

What are Butte County’s ADU requirements?

Butte County allows ADUs and JADUs in compliance with the California Government Code. Their requirements are as follows:

• There is no limit on the size of an ADU
• Setbacks:
  • None for conversions if its current dimensions are not being altered
  • Side and rear lot lines: 4 feet
  • In the State Responsibility Area, side and rear setbacks range from 30 to 100 square feet as specified by state law
  • In the Agricultural Budder Area, 300 square feet

Additional requirements may apply. Please consult with the county Development Services to ensure compliance with building and zoning regulations.

What are Calaveras County’s ADU requirements?

Calaveras County allows ADUs & Junior ADUs, so long as they meet the following requirements:

• ADUs cannot be Tiny Homes on Wheels, RVs, Yurts, or Storage Structures
• Minimum Square Footage: 150 sq. ft.
• Maximum Size:
  • Detached & Attached: 1,200 square feet
  • Conversion: no size limit
  • JADU: 500 square feet, plus 150 square feet for egress
• Setbacks: Vary based on where you reside

To confirm complete compliance, especially for setback requirements which vary based on where you reside, contact the Calaveras County Planning Department.

What are Colusa County’s ADU requirements?

Colusa County does permit accessory dwelling units, but the exact requirements are unclear. While they likely follow the state requirements, it’s still recommended that you check with the Community Development Department to confirm compliance. 

What are Contra Costa County’s ADU requirements?

Contra Costa permits accessory dwelling units and outlines the following provisions for them:

• Maximum Size:
  • Detached ADU: 1,000 square feet
  • Attached ADU: 1,000 square feet
  • Maximum square footage may be less, depending on exactly what zoning district you reside in
• Permanent foundation required for all ADUs
• Setbacks: 4 feet from side and rear property lines for detached ADUs and any ADU expanding on an existing structure’s square footage

Additional requirements may apply. Please verify ADU plans with the Contra Costa County Planning & Zoning Department.

What are Del Norte County’s ADU requirements?

Del Norte County has the following regulations in place for accessory dwelling units:

• Minimum Size: 150 square feet
• Maximum Size: 
  • JADU: 500 square feet
  • Conversions: 1,200 square feet
  • New Construction ADU: 1,200 square feet
• Setbacks:
  • Front: based on the zoning district
  • Side & rear: 4 feet
  • Separation between structures: 5 feet
• Maximum Height:
  • Attached ADUs: based on the zoning district
  • Detached ADUs: 16 feet
  • ADUs Above Detached Garage: 25 feet

For more specifics on types of ADUs and their exact requirements, visit this helpful county resource. If you have any questions or want to certify compliance with these requirements, contact the Del Norte County Planning Division.

What are El Dorado County’s ADU requirements?

El Dorado County outlines the following requirements for ADUs:

• Minimum Size: 220 square feet
• Maximum Size: 1,200 square feet

Additional requirements apply, but vary based on your property’s zoning and the type of ADU you plan to construct. To confirm compliance with all requirements, contact the county’s Planning Division.

What are Fresno County’s ADU requirements?

Fresno County allows both ADUs and JADUs, provided that they follow these standards:

• Types of ADUs Permitted:
  • Attached
  • Detached
  • Conversions
• Design: Must be consistent with that of the principal structure
• Maximum Size: 
  • Detached:
    • 850 square feet if less than a 2-bedroom
    • 1,000 square feet if it has two bedrooms
  • Attached:
    • Same as above or 50% of the floor area of the primary dwelling, whichever is less
• Number of Rooms: 2 bedrooms maximum
• Height:
  • Single-Story: 16 feet
  • Two-Story: Must comply with zoning district requirements
• Utilities: Must be new and separate from the principal residence

Many ADU requirements vary depending on the zoning district you reside in, so be sure to contact the Fresno County Planning Department to confirm compliance with all applicable regulations.

What are Glenn County’s ADU requirements?

Glenn County outlines the following requirements for ADUs, which they refer to as “second dwelling units”:

• There are no maximum size requirements, so long as it does not exceed the lot coverage requirements
• A permanent foundation is required
• Travel trailers, RVs, or other similar vehicles are not permitted as ADUs

Most ADU requirements are based on your property’s zoning, so be sure to confirm compliance with all applicable regulations with the Glenn County Planning Department.

What are Humboldt County’s ADU requirements?

Humboldt County outlines the following requirements for accessory dwelling units and JADUs:

• Minimum Size: None
• Maximum Size: 1,200 square feet
  • Can be larger with a Special Use Permit
  • Maximum of 500 square feet for JADUs
• Height: 16 feet or 26 feet on larger residentially zoned lots
• Setbacks: 4 feet for the side and rear yard lines
• Cannot be sold separately from the principal dwelling
• Cannot be rented for periods of 30 days or less

To ensure complete compliance, contact the Humboldt County Planning Department.

What are Imperial County’s ADU requirements?

Imperial County Planning & Development Services outlines the following requirements for ADUs:

• ADUs may be sold separately from the primary residence
• May be located in any zone that allows residential uses
• Maximum Size: 50% of the existing living area or 850 square feet, whichever is larger, or 1,000 square feet if the ADU has more than one bedroom
  • A detached ADU can be up to 1,200 square feet with a Conditional Use Permit (CUP)
• Setbacks: 4 feet from the side and rear property lines for detached ADUs or any ADU that expands on the original structure’s total square footage

Additional requirements do apply, but vary depending on the zoning district and type of ADU being constructed. Planning & Development Services can help you certify that your ADU plans meet all applicable regulations for your zoning district. 

What are Inyo County’s ADU requirements?

The requirements for building an ADU in Inyo County are as follows:

• # of ADUs:
  • Single-Family Residential Zones: 1 ADU & 1 JADU
  • Multifamily Residential Zones: 2 detached ADUs or no more than 25% of the existing units in the multifamily building, or conversion of existing non-habitable space. JADUs are not allowed.
• Maximum Size:
  • Detached ADUs: 1,200 square feet
  • Attached ADUs: 1,200 square feet or 50% of the floor area of the primary residence
  • JADUs: 500 square feet
  • ADUs can be a maximum of 800 square feet, regardless of floor area ratio or lot area requirements

Additional requirements are in place,  but vary based on zoning district and type of ADU being built. To confirm compliance with all applicable regulations, contact the Inyo County Planning Department.

What are Kern County’s ADU requirements?

Kern County’s ADU requirements are as follows:

• Minimum Lot Size: 
  • 7,500 square feet if the lot is served by both a community water supply & public sewer
  • ½ acre if served by a community water supply & private septic system
  • 1 acre if not served by a community water system or public sewer
• The principal dwelling must be at least 1,200 square feet
• Number of ADUs Per Lot: 1
• Maximum Size: 
  • Attached/Interior Conversion: 1,200 square feet or 50% of the total floor area of the principal dwelling, whichever is less
  • Detached: 1,200 square feet
• Setbacks: Follow the applicable setbacks for the zoning district in which the ADU is located

Since setbacks and other requirements vary by zoning district, contact the Kern County Planning Department to confirm your property’s zoning and ensure compliance with all applicable regulations.

What are Kings County’s ADU requirements?

Kings County outlines the following development conditions for ADUs:

• Maximum Size: 1,000 square feet of heated floor area, 1,000 square feet of unheated floor area
  • This can vary depending on the type of ADU constructed and where it’s being built

Additional requirements do apply, but they vary based on your property’s zoning and the type of ADU you plan to construct. Contact the Kings County Community Development Agency to ensure compliance.

What are Lake County’s ADU requirements?

Lake County follows the California Department of Housing & Community Development’s standards for accessory dwelling units. Specific requirements such as size and placement often vary based on your property’s zoning, so be sure to certify compliance with the Lake County Planning Department. 

What are Lassen County’s ADU requirements?

Lassen County allows a “second housing unit,” which may require express approval from the Planning Commission. There are no standard ADU requirements due to limited access to public water, sewer, and fire services within the county. If you’re interested in adding a secondary dwelling unit to your property, contact the Lassen County Planning Commission.

What are Los Angeles County’s ADU requirements?

Los Angeles County outlines the following requirements for ADUs:

• Maximum Size:
  • Detached ADU: 1,200 square feet
  • Attached/Converted ADU: 50% of the floor area of the principal dwelling unit
  • JADU: 500 square feet

Additional requirements apply. Confirm compliance with the Los Angeles County Planning Department.

What are Madera County’s ADU requirements?

Madera County outlines the following development standards for ADUs:

• Maximum Size:
  • Detached ADU: 850 sq. ft. for 1-bedroom or 1,000 sq. ft. for 1 bedroom or more
  • Attached ADU: 50% of the existing primary dwelling or the 850/1,000 sq.ft. requirement based on the number of rooms, whichever is greater
  • JADU: 500 square feet
  • Conversions: Varies based on whether the structure is attached or detached
• Setbacks:
  • Detached ADU: 
    • Front: Same as primary dwelling
    • Side & Rear: 4 feet
  • Attached ADU:
    • Front: Same as primary dwelling
    • Side & Rear: 4 feet
  • Conversions: None if the square footage of the original structure is not being altered

Some requirements vary based on your property’s zoning. Contact the Madera County Planning Division to ensure complete compliance. 

What are Marin County’s ADU requirements?

Marin County’s ADU requirements fall into two categories, each with its own set of standards:

• Category 1: Statewide Exemption
  • Single-Family Development
    • Maximum Size: 800 square feet
    • Rear & Side Yard Setback: 4 feet
  • Multi-family Development
    • Maximum Size: 800 square feet
    • Maximum Height: 18 feet
    • Side & Rear Setbacks: 4 feet
  • Must comply with state requirements
• Category 2: Permit
  • These ADUs are subject to Accessory Dwelling Unit Permit Approval
  • Attached ADUS
    • Maximum Size: 50% of the floor area of the existing residence or 1,200 square feet, whichever is less
      • 850 square feet maximum permitted for a 1-bedroom ADU, regardless of the above requirements
      • 1,000 square feet maximum permitted for 2-bedroom or more ADUs, regardless of the above requirements
  • Detached ADUs
    • Maximum Size: 1,200 square feet
      • 850 square feet maximum permitted for a 1-bedroom ADU, regardless of the above requirements
      • 1,000 square feet maximum permitted for 2-bedroom or more ADUs, regardless of the above requirements

Contact the Marin County Community Development Agency to determine which category your ADU falls into and to confirm compliance with zoning district standards.

What are Mariposa County’s ADU requirements?

Mariposa County follows the same ADU requirements set forth by the state, including the following:

• ADUs cannot be Tiny Homes on Wheels, RVs, Yurts, or Storage Structures
• Minimum Square Footage: 150 sq. ft.
• Maximum Size:
  • Detached & Attached: 1,200 square feet
  • Conversion: no size limit
  • JADU: 500 square feet, plus 150 square feet for egress
• Setbacks: Vary based on where you reside

Contact the Mariposa County Planning Department for the exact requirements in your area. 

What are Mendocino County’s ADU requirements?

Mendocino County outlines the following basic requirements for accessory dwelling units:

Maximum Size:

• Detached ADUs: Up to 1,200 square feet
  
• Attached ADUs: Up to 50% of the existing living area or 1,200 square feet, whichever is smaller
  

Depending on the nature of your questions, you can contact either the Building Division or the Planning Division for more detailed information.

What are Merced County’s ADU requirements?

Merced County’s ADU requirements are as follows:

• # of ADUs Permitted Per Parcel:
  • Parcels With Single-Family Dwellings: 1 JADU & 1 either detached, attached, or conversion ADU
  • Parcels With Multi-Family Dwellings: 2 detached ADUs or the number of converted ADUs cannot exceed 25% of the total number of dwelling units
• Maximum Floor Area:
  • Detached ADU: 1,200 square feet
  • Attached/Converted ADU: 50% of the living area of the principal dwelling unit or 1,200 square feet, whichever is less
  • JADU: 500 square feet
• Setbacks: 4 feet from side and rear property lines unless converting an existing structure

Additional requirements may apply depending on your property’s zoning and the type of ADU you plan to build. Contact the Merced County Planning Department to confirm the details of your project.

What are Modoc County’s ADU requirements?

Modoc County follows the state’s ADU requirements, which include the following: 

• ADUs cannot be Tiny Homes on Wheels, RVs, Yurts, or Storage Structures
• Minimum Square Footage: 150 sq. ft.
• Maximum Size:
  • Detached & Attached: 1,200 square feet
  • Conversion: no size limit
  • JADU: 500 square feet, plus 150 square feet for egress
• Setbacks: Vary based on where you reside

Contact the Modoc County Planning Department to ensure your ADU complies with county requirements.

What are Mono County’s ADU requirements?

Mono County enforced the following standards for accessory dwelling units:

• The maximum size for an ADU will vary depending on the size of your property.
  • For properties with 7,500 square feet or less: 500 square feet
  • For properties with 7,500 to 10,000 square feet: 640 square feet
  • For properties with 1 acre or more: Up to 1,400 square feet with a use permit
• Design: Must be consistent with the primary structure

Contact the Mono County Planning Division to certify compliance with all applicable regulations.

What are Monterey County’s ADU requirements?

ADUs in Monterey County must be built in accordance with the following standards:

• Detached ADUs:
  • Maximum Size: 800 square feet
  • Setbacks: 4 feet from the side and rear property lines
  • Maximum Height: 16 feet
• Attached/Conversion ADUs:
  • Maximum Size: Cannot expand more than 150 square feet outside of the existing dimensions of the structure to which the ADU is being added
  • Setbacks: Side and rear lot line setbacks must be sufficient for fire & safety

Additional requirements apply depending on the zoning district where you plan to place your ADU. Contact Monterey County Planning Services to ensure compliance with zoning requirements in those areas. 

What are Napa County’s ADU requirements?

Napa County allows accessory dwelling units as long as they comply with the state’s requirements for adding them to a property. To confirm the exact size, placement, and zoning requirements for your property and ADU plans, contact Napa County’s Building Division.

What are Nevada County’s ADU requirements?

Nevada County’s ADU requirements are as follows:

• Permitted Zoning Districts: R1, R2, RA, AE, AG, FR, & TPZ
• # of ADUs Per Property: 1 ADU & 1 JADU
• Maximum Size:
  • Detached ADUs: 1,200 square feet
  • Attached ADUs: 50% of the existing residence’s gross floor area or no larger than 1,200 square feet
• Setbacks: 4 feet from the side and rear yard lines

Many ADU requirements are based on your property’s zoning designation. Review your ADU plans with the Nevada County Planning Department to ensure full compliance.

What are Orange County’s ADU requirements?

Orange County allows ADUs so long as they comply with the following requirements on the number of units, size, location, and more:

• # of Units: 1 ADU & 1 JADU (as long as one structure on the lot is owner-occupied)
• Maximum Size:
  • Attached ADU: 50% of the area of the primary dwelling unit or 1,200 square feet, whichever is less
  • Detached ADU: 1,200 square feet within the building site area or 800 square feet within the setback area where permitted
  • Conversion: Shall not exceed the square footage of the converted structure, following the size requirements above
• Setbacks:
  • Front: Not permitted
  • Side & Rear: 4 feet from all property lines
• Maximum Height: 16 feet

Since many of these requirements vary depending on the zoning district in which the ADU is being placed, be sure to confirm compliance with the Orange County Public Works Department.

What are Placer County’s ADU requirements?

Placer County’s ADU requirements are as follows:

• # of ADUs Allowed Per Property: 1 ADU & 1 JADU
• Maximum Size:
  • Detached ADU: 1,200 square feet
  • Attached ADU: Up to 50% of the primary dwelling unit’s square footage
  • JADU: 500 square feet

Additional requirements regarding ADUs can be found on the Placer County FAQ page. Depending on the requirements you had questions about, contact Placer County Planning or Building Services to certify compliance.

What are Plumas County’s ADU requirements?

Plumas County allows ADUs on all single-family residentially zoned parcels (2-R, 3-R, and 7-R) that are no more than 1,200 square feet. The county allows attached, detached, and conversion ADUs with different requirements. Additionally, requirements vary based on your property’s zoning designation, so be sure to reach out to the Plumas County Planning Department to certify compliance.

What are Riverside County’s ADU requirements?

ADUs must comply with the following standards in Riverside County:

• Maximum Size:
  • Detached ADU: 1,000 square feet
  • Attached ADU: 50% of the primary dwelling’s floor area or 800 square feet, whichever is greater, but it should never exceed 1,000 square feet
  • JADU: 500 square feet
• Setbacks: 4 feet from side and rear property lines, front yard setbacks must comply with zoning district standards

Since many ADU requirements depend on your property’s zoning designation, contact the Riverside County Planning Department to learn about all applicable regulations.

What are Sacramento County’s ADU requirements?

To build an ADU or JADU in Sacramento County, you must comply with the following development standards:

• # of ADUs Per Property:
  • Single-Family/Half-Plex: 1 ADU & 1 JADU
  • Mulifamily: 2 detached ADUs, 25% of total unit count in ADUs converted from existing non-living space
• Minimum Size: 150 square feet
• Maximum Size:
  • Detached ADU: 1,200 square feet
  • Attached ADU: 50% of primary dwelling or 800 square feet, whichever is greater
  • JADU: 500 square feet

Additional requirements apply. Contact the Sacramento County Planning Department to ensure complete compliance with all applicable regulations.

What are San Benito County’s ADU requirements?

San Benito County adheres to state laws regarding accessory dwelling units, including:

• Number of ADUs Per Property: 2
• Maximum Size: 800-1,200 square feet
• Setbacks: 4 feet from the side and rear property lines
• Maximum Height: 16 feet

Additional requirements may apply. Contact San Benito County’s Planning Department for properties in unincorporated areas, or reach out to your local officials to learn about requirements in your jurisdiction.

What are San Bernardino County’s ADU requirements?

San Bernardino County outlines the following requirements for ADUs:

• Lot Coverage Requirements: None apply for ADUs that are 800 square feet or less
• Setbacks: 4 feet from the side and rear property lines
• Maximum Square Footage: 800
• Maximum Height: 16 feet

Contact San Bernardino Land Use Services to certify that your ADU meets all applicable requirements.

What are San Diego County’s ADU requirements?

San Diego outlines the following ADU requirements for those residing in unincorporated areas:

• Maximum Size;
  • Detached ADU: 1,200 square feet
  • Attached ADU: Up to 50% of the square footage of the existing single-family residence or 1,200 square feet, whichever is less
  • JADU: 500 square feet
• Setbacks:
  • Detached ADU: 4 feet from side & rear yards, front yard setbacks based on zoning district
  • Attached ADU: 4 feet from side & rear yards, front yard setbacks based on zoning district

Additional requirements may apply. Since they are often contingent on your property’s zoning designation, reach out to San Diego Planning & Development Services to ensure complete compliance. 

What are San Francisco County’s ADU requirements?

San Francisco allows accessory dwelling units so long as they comply with the following standards:

• Minimum Size: 220 square feet
• Minimum Ceiling Heights: 7.5 feet
• Maximum Size: Only the RH-1(S) zoning district outlines a maximum size, which is 600 square feet

It’s always best to contact the Planning Department to confirm compliance, as zoning regulations for your district often determine your ADU’s size, placement, allowable number, and more.

What are San Joaquin County’s ADU requirements?

The requirements for placing an ADU on your property in San Joaquin County are as follows:

• Number of ADUs: 1 ADU & 1 JADU
• Permits:
  • Building Permit: JADUs, conversion ADUs, and detached ADUs that are 16 feet in height or less, 800 square feet in floor area, and setback 4 feet from property lines require this
  • ADU Permit: Any ADU that doesn’t meet the criteria listed above requires an ADU permit
• Maximum Size:
  • In R-VL, R-L, R-M, and R-MH Zones: 850 square feet or 1,000 square feet if there is more than 1 bedroom
  • Attached ADU: 50% of the floor area of the primary dwelling

Additional requirements apply based on which zoning district you reside in. To get a full understanding of all the regulations you must follow, contact the San Joaquin Community Development Department.

What are San Luis Obispo County’s ADU requirements?

The following requirements are in place for accessory dwelling units in unincorporated parts of San Luis Obispo County:

• Different requirements are in place depending on whether you live in a Coastal Zone or an Inland area
• ADUs are not permitted in the Cambria Community Services District boundary, and within the Los Osos Groundwater Basin boundary and plan area
• For Inland Areas, the ADU requirements are as follows:
  • Minimum Size: 150 square feet
  • Maximum Size: 1,200 square feet
  • Setbacks: Must comply with zoning district requirements

Since ADU requirements can vary by zoning district and whether you reside in an inland or coastal zone, it’s recommended that you contact the San Luis Obispo County Planning Department to ensure compliance with all applicable regulations.

What are San Mateo County’s ADU requirements?

San Mateo County has different  ADU ordinances in place depending on whether you reside in a coastal or non-coastal zone. These requirements can vary, but are similar in the following ways:

• Maximum Floor Area:
  • Detached ADUs: 800 square feet or 35% of the livable floor area of the existing or proposed primary structure, whichever is larger, up to a maximum of 1,500 square feet
  • Attached ADUs: 800 square feet or 35% of the livable floor area of the existing or proposed primary structure, whichever is larger, up to a maximum of 1,500 square feet
  • JADU: 500 square feet
• Setbacks: 4 feet from side and rear property lines at least, all other setback requirements must match those in place for your zoning district

Since ADU requirements are contingent on your zoning district or whether you reside in a coastal or non-coastal zone, it’s recommended that you reach out to the San Mateo County Planning Department to ensure complete compliance. 

What are Santa Barbara County’s ADU requirements?

Santa Barbara County has ADU requirements that vary depending on whether you live in an inland or coastal zone, but they share the following similarities:

• Maximum Size: 800 square feet in S-F zone, 1,200 square feet in multifamily zone
• Maximum Height: 16 feet
• Setbacks: Must comply with your zoning district’s requirements
• Design: Must be consistent with that of the primary dwelling

Additional requirements do apply and can vary depending on where you reside. Contact the Santa Barbara County Planning Department to certify compliance with all applicable regulations.

What are Santa Clara County’s ADU requirements?

Santa Clara County has the following laws in place regarding accessory dwelling units:

• Number of ADUs Per Property: 1 ADU & 1 JADU
• Maximum Size: 1,200 square feet or 50% of the primary residence’s square footage if it’s an attached ADU, so long as that allows for a minimum of 800 square feet
• Setbacks: 4 feet for side & rear yards, front yard based on zoning district requirements

Additional requirements apply, so be sure to certify compliance with the Santa Clara County Planning Department. 

What are Santa Cruz County’s ADU requirements?

The requirements for ADUs in Santa Cruz County are as follows:

• Permits: Building permit required, additional permitting may be required to make changes to a non-conforming dwelling or for ADUs in the coastal zone
• Number of ADUs: 1 ADU & 1 JADU on properties with single-family dwellings, 2 detached ADUs, and 25% of units can have ADU conversions on properties with multifamily dwelling units
• Minimum Size: 150 square feet
• Maximum Size: 
  • JADU: 500 square feet
  • Attached ADU: 850-1,000 square feet or 50% of the primary dwelling unit, whichever is less, if the property is less than an acre, or just 50% of the primary dwelling unit’s floor area if the property is greater than an acre
  • Detached ADUs: For less than an acre, 800 for 1 bedroom and 1,000 for two bedrooms or more, for properties with more than an acre 1,200 square feet

Additional requirements apply based on the zoning district in which you reside. Contact the Santa Cruz County Planning Department to certify compliance with all applicable regulations.

What are Shasta County’s ADU requirements?

Shasta County has the following ADU requirements in place:

• Number of ADUs Per Lot: 1
• Maximum Size: 1,200 square feet or 50% of the primary residence’s floor area, whichever is less, unless it is less than 640 square feet, in which case it must be at least 640 square feet
• Setbacks: 5 feet from side & rear lot line, front setbacks based on zoning district
• Design: Must be consistent with the principal structure

To confirm compliance with regulations based on your zoning district, contact the Shasta County Planning Department. 

What are Sierra County’s ADU requirements?

Sierra County’s ADU requirements are as follows:

• Number of ADUs: 2 ADUs & 1 JADU
• Setbacks:
  • Attached: None unless expanding upon an existing structure
  • Detached: 4 feet minimum from side & rear property lines, front yard setback based on zoning district requirements
• Maximum Size: 1,200 square feet

Additional requirements apply based on the zoning district in which you reside. Be sure to contact the Sierra County Planning Department to ensure compliance with all applicable regulations.

What are Siskiyou County’s ADU requirements?

Accessory dwelling units are permitted in Siskiyou County, which even offers pre-approved plans. Exact requirements are unclear, so reach out to the Siskiyou County Planning Department for clarification on what development standards you must follow for your ADU.

What are Solano County’s ADU requirements?

Solano County has the following regulations in place for accessory dwelling units:

• Minimum Size: 380 square feet
• Maximum Size:
  • Attached ADU: 50% of the primary dwelling unit’s floor area up to 1,200 square feet
  • Detached ADU:
    • R-TC Zoning: 800-1,000 square feet, depending on the number of bedrooms
    • R-R Zoning: 1,500 square feet
  • JADU: 500 square feet
• Setbacks:
  • Side & Rear Yard Lines: 4 feet
  • Front Yard: Based on zoning districts

To confirm which requirements apply based on your zoning district, contact Solano County Planning Services.

What are Sonoma County’s ADU requirements?

Sonoma County’s ADU requirements are as follows:

• Permits Required: Building Permit
• Maximum Size: 1,200 square feet
• Number of ADUs Allowed:
  • On Lot With Single-Family Dwelling: 1 attached ADU & 1 detached ADU
  • On Lot With Existing Multifamily Dwelling: 2 detached ADUs & 25% of existing units converted from non-livable space
  • On Lot With A Proposed Multifamily Dwelling: 2 detached ADUs
• Setbacks:
  • Front Yard: Determined by zoning unless it would prevent an 800 square foot ADU
  • Side & Rear Yard: Minimum 4 feet

Since requirements can vary based on zoning, be sure to contact the Sonoma County Planning Division to certify compliance with all applicable regulations.

What are Stanislaus County’s ADU requirements?

The following standards are in place for ADUs in Stanislaus County:

• Maximum Size: 1,200 square feet
• Setbacks:
  • Side & Rear Yard: 4 feet
  • Front Yard: Based on your zoning district

Many requirements for ADU construction are based on your zoning district. To ensure complete compliance, contact the Stanislaus County Planning Department.

What are Sutter County’s ADU requirements?

Accessory dwelling units in Sutter County are subject to the following requirements:

• Permits: Zoning Clearance & Building Permit
• Number of Units: 1
• Maximum Size:
  • Detached ADU: 1,200 square feet
  • Attached ADU: 50% of the primary dwelling unit’s floor area or 1,200 square feet, whichever is less

Additional requirements apply to ADUs. To ensure full compliance, confirm the details of your project with the Sutter County Planning Services.

What are Tehama County’s ADU requirements?

Accessory dwelling units in Tehama County must adhere to these requirements:

• Maximum Size: 
  • Detached ADU: 1,200 square feet
  • Attached ADU: 50% of the existing living area or 1,200 square feet, whichever is less
• Setbacks:
  • Front Yard: Based on zoning
  • Side & Rear Yard: 5 feet

To certify compliance with all applicable regulations, contact the Tehama County Planning Department.

What are Trinity County’s ADU requirements?

Trinity County does allow ADUs, but specific requirements are unclear. To understand what’s allowed on your property, contact the Planning Division for guidance.

What are Tulare County’s ADU requirements?

Tulare County permits ADUs, but the exact requirements for them are unclear. For clarification on what is allowed, contact the county’s Planning Department.

What are Tuolumne County’s ADU requirements?

Tuolumne County has the following development standards in place for ADUs within the county:

• Maximum Size: 
  • Detached ADU: 1,200 square feet
  • Attached ADU: 50% of the primary dwelling unit floor area or 1,200 square feet, whichever is less
• Required Rooms: Bathroom, kitchen, & living/dining room
• Setbacks: 
  • Side & Rear Yard: Minimum of 5 feet
  • Front Yard: Based on zoning requirements

Additional requirements are in place and often vary by your property’s zoning designation. To certify compliance with all applicable regulations, contact the Tuolumne County Development Department.

What are Ventura County’s ADU requirements?

Accessory dwelling units in Ventura County must adhere to the following requirements:

• Number of ADUs: 1 ADU & 1 JADU
• Maximum Size:
  • Detached ADU: 850 square feet on property with single-family dwelling, 1,200 square feet on properties with multifamily dwellings
  • JADU: 500 square feet

Additional requirements apply, but are based on the type of ADU you plan to build and the zoning district in which you reside. The best way to ensure your ADU plans are in compliance with these requirements is to contact the Ventura County Planning Department.

What are Yolo County’s ADU requirements?

The following requirements are in place for ADUs being added to properties within Yolo County:

• Maximum Height: 16 feet
• Setbacks for New Construction:
  • Side & Rear Yard:  4 feet
  • Front Yard: Based on zoning 
• Building Separation: Detached structures must be at least 10 feet from the principal structure
• Maximum Size:
  • Detached ADUs: 1,200 square feet
  • Attached ADUs: 50% of the existing structure’s living area or 1,200 square feet, whichever is less

To ensure compliance with all applicable requirements, contact the Yolo County Planning Division.

What are Yuba County’s ADU requirements?

ADU requirements in Yuba County are as follows:

• Maximum Size: 
  • Detached ADU: 1,200 square feet
  • Attached ADU: 50% of the existing primary dwelling unit’s square footage or 1,200 square feet, whichever is less
  • JADU: 500 square feet
• Rear/Side Setbacks: 4 feet
• Front/Street Setback: Based on the zoning district
• Number of ADUs: 1 ADU + 1 JADU

Additional requirements are in place. To certify compliance with these regulations, contact the Yuba County Planning Department.

What Cities in California Allow ADUs?

Below are several California cities, along with summaries of their ADU requirements. Because each municipality may have different sizes and placement rules based on zoning, we’ve also included contact information for the appropriate zoning official to help you confirm what applies to your property.

Does Clovis, CA, Allow ADUs?

Yes, Clovis allows accessory dwelling units and even has a Cottage Home Program, which helps city residents construct an ADU on their property. 

Clovis, CA ADU Requirements

The requirements for adding an ADU to your property in Clovis are as follows:

• Detached ADU:
  • Max Size: 1,200 square feet
  • Front Setback: Based on your zoning district
  • Side & Rear Setback: 4 feet
  • Number of Units: 1 ADU & 1 JADU
• Attached ADU:
  • Max Size: 50% of the existing primary dwelling unit or 1,200 square feet
  • Front Setback: Based on your zoning district
  • Side & Rear Setback: 4 feet
  • Number of Units: 1 ADU & 1 JADU

If you have questions about these requirements or want to confirm front setback requirements, contact the Clovis Planning & Development Department. 

Does Dinuba, CA, Allow ADUs?

Yes, Dinuba permits accessory dwelling units in all RA, R, and RM zoning districts as long as they meet the requirements outlined below.

Dinuba, CA ADU Requirements

• Number of Units: 1
• Appearance: Consistent with that of the principal structure and existing structures in the neighborhood
• Minimum Size: 150 square feet
• Maximum Size: 
  • Detached ADU: 1,200 square feet
  • Attached ADU: 50% of the floor area of the primary residence
• Tiny homes ARE permitted as detached ADUs so long as they comply with ANSI 119.2 or 119.5 standards

If you have any questions about setbacks or permitting requirements for your ADU, contact the Dinuba Planning & Development Department.

Does Exeter, CA, Allow ADUs?

It is unclear what they allow at this time. To find out if ADUs are permitted, contact the Exeter Planning & Development Department.

Does Fresno, CA, Allow ADUs?

Yes, Fresno allows ADUs that meet the standards outlined below.

Fresno, CA ADU Requirements

• Number Allowed: Depends on zoning district
• Minimum Size: None, although there must be at least one habitable room of 70 square feet
• Maximum Size: 
  • Attached ADU: 50% of the existing home’s floor area or 1,200 square feet, whichever is less
  • Detached ADU: 1,200 square feet
• Setbacks: 
  • Front Yard: Based on your zoning district
  • Side & Rear Yard: 4 feet

Since many ADU requirements in Fresno are based on your zoning district, consult with the city’s Planning & Development Department. 

Does Hanford, CA, Allow ADUs?

Yes, the city does permit ADUs. Below, you can learn more about the requirements for adding one to your property.

Hanford, CA ADU Requirements

• Number of Units: Depends on your property’s zoning
• Maximum Size: 
  • Detached ADU: 1,200 square feet
  • Attached ADU: 50% of the primary dwelling or 850 square feet for a 1-bedroom or 1,000 square feet for a 1-bedroom or more, whichever is greater
• Minimum Setbacks:
  • Front Yard: Based on your zoning district
  • Side & Rear Yard: 4 feet

Since many ADU requirements vary based on zoning, confirm compliance with the Hanford Community Development Department. 

Does Kerman, CA, Allow ADUs?

Yes, Kerman allows ADUs as long as they comply with the city’s established requirements.

Kerman, CA ADU Requirements

• Number Per Lot:
  • Single-Family: 1 ADU & JADU
  • Multi-Family: 2 detached ADUs and converted ADUs may not exceed 25% of the number of dwelling units
• Maximum Size:
  • 1-bedroom: 850 square feet
  • 2+ bedrooms: 1,000 square feet
• Setbacks:
  • Front Yard: Varies based on zoning & type of ADU
  • Side & Rear Yard:  4 feet

Since requirements can vary based on zoning or project plans, consult with the Planning Division to clarify what’s allowed. 

Does Kingsburg, CA, Allow ADUs?

Kingsburg may permit ADUs based on Fresno County or state standards, but local regulations are not clearly outlined. Contact the Planning Division to confirm what’s allowed.

Does Lemoore, CA, Allow ADUs?

Yes, the city permits ADUs under the following provisions:

Lemoore, CA ADU Requirements

• Minimum Lot Size: 5,000 square feet
• Number Per Lot: 1
• Owner-Occupancy: Required
• Maximum Size:
  • Attached ADU: 30% of the existing living area of the primary dwelling
  • Detached ADU: 1,200 square feet
• Setbacks: Based on your zoning district’s requirements
• Permit: Required

To obtain a permit or get answers to any additional questions you may have, contact the Lemoore Community Development Department. 

Does Los Angeles, CA, Allow ADUs?

Yes, Los Angeles permits ADUs as long as they meet specific standards. 

Los Angeles, CA ADU Requirements

• Minimum Size: 150 square feet
• Maximum Size: 
  • Detached ADU: 1,200 square feet
  • Attached ADU:  50% of the primary dwelling’s floor area
    • However, it cannot be less than 850 square feet for a 1-bedroom or 1,000 square feet for a multi-bedroom ADU
• Movable tiny houses are permitted as ADUs

Additional requirements apply. Contact the Department of Building & Safety to ensure compliance.

Does Madera, CA, Allow ADUs?

The city of Madera does permit ADUs, but the exact requirements are unclear. Contact the Planning Department for clarification on what is allowed.

Does Orange Cove, CA, Allow ADUs?

Yes, Orange Cove permits accessory living quarters, which appear similar to ADUs. For specific requirements, contact the Orange Cove Building & Engineering Department.

Does Reedley, CA, Allow ADUs?

Yes. Reedley permits ADUs that meet the following standards. 

Reedley, CA ADU Requirements

• Number Per Parcel: 
  • With Single-Unit Dwelling: 1 ADU & 1 JADU
  • With Multiple Detached Single-Unit Dwellings: 1 ADU
  • With Multi-Unit Dwellings: 2 ADUs
• Setbacks:
  • Front Yard: Based on your zoning district
  • Side & Rear Yard: 4 feet
• Minimum Size: 150 square feet
• Maximum Size:
  • Attached ADU: 50% of the living area of the primary dwelling or 1,200 square feet, whichever is greater
  • Detached ADU: 1,200 square feet

To ensure compliance with all applicable requirements, contact the Community Development Department. 

Does Selma, CA, Allow ADUs?

Yes, Selma allows accessory dwelling units provided that they meet the following requirements:

Selma, CA ADU Requirements

• Minimum Size: 150 square feet
• Maximum Size:
  • Attached ADU: 50% of the main residence or 1,000 square feet, whichever is less
  • Detached ADU: 1,000 square feet
• Number Per Lot: 1 ADU & 1 JADU

Additional requirements may apply. Contact the Building Department to ensure compliance with all applicable regulations.

Does Tulare, CA, Allow ADUs?

Yes, Tulare does allow ADUs. The city’s requirements are as follows:

Tulare, CA ADU Requirements

• Number Per Lot: 1
• Maximum Size:
  • Attached ADU: 50% of the existing living area of the principal unit or 1,200 square feet, whichever is less
  • Detached ADU: 1,200 square feet
• Space Between Buildings: Ten feet between principal structure and detached ADU

Contact the Tulare Community Development Department to learn more about setbacks and permitting requirements. 

Does Visalia, CA, Allow ADUs?

Yes, Visalia allows accessory dwelling units, provided that they adhere to the following standards of development:

Visalia, CA ADU Requirements

• Number Per Lot: Depends on zoning
• Owner-Occupancy: Not required
• Minimum Open Space: Based on zoning 
• Permanent Foundation: Required
• Maximum Size:
  • Attached ADU: 50% of the primary dwelling unit’s floor area or  850 square feet if 1-bedroom or less, 1,200 square feet with 2-bedrooms or more, whichever is less
  • Detached ADU: 850 square feet if 1-bedroom or less, 1,200 square feet with two bedrooms or more
• Minimum Setbacks
  • Front Yard: Based on your zoning district
  • Side & Rear Yard: 4 feet

To confirm compliance with all applicable regulations, contact the Visalia Planning Department. 

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