California ADU Rules (2024)

Interpreting all the moving parts within your city or county can be overwhelming, confusing, and frustrating for many homeowners when trying to build an ADU.

As a design-build general contractor, we work with you to navigate the difficult process of understanding and building an ADU within state laws including:

• What’s possible for your property and building budget.
• Architectural blueprints and interior design.
• City and county ADU planning and building department approvals.
• Construction permits.

What You Need to Know About Building an ADU in Your City

1. Accessory Dwelling Unit and City Ordinance Terms and Definitions:
   
   • Accessory Dwelling Unit (ADU): An ADU is defined as an attached or a 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.
   • Junior Accessory Dwelling Unit (JADU): A JADU is defined as an ADU no more than 500 square feet in size and contained entirely within a single-family residence. A JADU can only be created through conversion of an existing portion of a single family dwelling (SFD), not a garage or other accessory building.
   • Single-family Dwelling (SFD)/Duplex: One dwelling unit in one building, not including an ADU or JADU. A duplex, two dwelling units in one building, is treated as an SFD and not a multi-family dwelling (MFD) for the purposes of determining the number, type, and development standards of ADU/JADUs.
   • Multi-family Dwelling (MFD): Three or more dwelling units in one building, not including an ADU or JADU.
2. Three Per Lot Single Family: There is a limit to three ADUs (one junior and one detached) per residential lot zoned for single-family residences with a single-family residence already built on the lot (triplex).
3. Rental Terms: Local government agencies may require that the property be used for rentals of terms longer than 30 days. Vacation rentals may not be permitted.
4. Owner Occupancy Requirements: Cities cannot require owner occupancy until 2025. However, should a property have both an ADU and JADU, JADU law requires owner-occupancy of either the newly created JADU, or the single-family residence.
5. Separate Entrance: An ADU must have its own separate entrance.
6. Bathroom: An ADU must include the minimum of a 3/4 bath (a toilet, sink, and a shower). A JADU may include separate sanitation facilities or may share sanitation facilities with the existing structure.
7. Kitchens: An ADU must include permanent provisions for living, sleeping, eating, and cooking, on the same parcel as the single-family or multifamily dwelling is or will be situated. If a JADU does not share kitchen facilities with the primary dwelling, it must be provided with its own kitchen.
8. Fire Sprinklers: ADUs are to be considered part of the single-family residence for the purposes of fire and life protection ordinances and regulations, such as sprinklers and smoke alarms. ADUs shall not be required to provide fire sprinklers if they were not a requirement for the primary residence. If the multifamily structure is served by fire sprinklers, the ADU can be required to install fire sprinklers.
9. Historic district or Designated Historic Landmark: An additional planning and building department review and approval is required to obtain a Certificate of Appropriateness “COA” prior to the application for building permits for the construction of an ADU.
10. City Approval and Hearings: A building permit will be reviewed within 60 days of submittal. If there is no existing SFD or MFD on the property, or an ADU is proposed with a new SFD/MFD, the city may not act on the ADU/JADU until it acts on the SFD/MFD, and the 60-day timeline does not begin until the city acts on the SFD/MFD.
11. Minimum Size: An ADU must have a minimum living area of 150 square feet.
12. Garage Conversions and Previously Permitted Accessory Buildings for Single Family and Duplex: The conversion of garages, sheds, barns, and other existing accessory structures, either attached or detached from the primary dwelling, into an ADU is permitted.

    The conversions of accessory structures are not subject to any additional development standard, such as unit size, height, and lot coverage requirements, and shall be from existing space that can be made safe under building and safety codes. A city and county ordinance cannot set limits on when the structure was created, and the structure must meet standards for health and safety.

    An ADU created within an existing accessory structure may be expanded up to 150 square feet without application of local development standards, but this expansion shall be limited to accommodating ingress and egress such as a stairwell to reach a second story.

    Public improvements are beyond what is required for the creation of an ADU, as per state law. For example, an applicant shall not be required to improve sidewalks, carry out street improvements, or access improvements to create an ADU. Additionally, as a condition for ministerial approval of an ADU, an applicant shall not be required to correct nonconforming zoning conditions..

13. New Construction and Room Addition ADU Attached to Single Family Residence: A city or county is required to approve any attached or detached ADU under 1200 square feet unless the city adopts a new ADU ordinance setting local government standards for a single-family zoned lot. If a city adopts such an ordinance it must follow two restrictions: One, no maximum unit size limit under 850 square feet (or 1000 square feet for a two-bedroom ADU). Two, a floor area ratio must allow development of at least one 800 square feet attached or detached ADU on every lot.
14. Single Story Height Limit and Property Line Setbacks: The height limit for a single story ADU is 16 feet with a side and rear setback of four feet. Front yard setbacks as required by local ordinance.
15. Second Story Height Limit and Setbacks: The height limit and setback requirements for a two-story ADU is dependent on local ordinance.
16. Lot Requirements and Coverage: There are no minimum lot size requirements for an existing legal lot. Any newly created lot must comply with local zoning regulations.
17. Number of Bedrooms: State ADU law does not allow for the limitation on the number of bedrooms of an ADU. A limit on the number of bedrooms could be construed as a discriminatory practice towards protected classes, such as familial status, and would be considered a constraint on the development of ADUs.
18. Development and Impact Fees: ADUs that are 750 square feet and smaller are not subject to impact fees by California State Law. Should an ADU be 750 square feet or larger, impact fees shall be charged proportionately in relation to the square footage of the ADU to the square footage of the primary dwelling unit.
19. Homeowners Associations: An HOA must allow the construction of ADUs.
20. Utility Fee Requirements for Conversions: Where ADUs are being created within an existing structure (primary or accessory), new or separate utility connections and fees (connection and capacity) are not required. Where ADUs are being created with a new primary residence new or separate utility connections and fees (connection and capacity) are required based on its square footage or plumbing fixtures as compared to the primary dwelling.
21. Solar Panel Requirements: New constructed ADUs are required to provide solar panels if the unit(s) is a newly constructed detached ADU. The panels can be installed on the ADU or on the primary dwelling unit. ADUs that are constructed within existing space, or as an addition to existing homes, including detached additions where an existing detached building is converted from non-residential to residential space, are not required to provide solar panels.
22. Parking: One parking stall required per ADU unless any of the following are met:
    • Accessory dwelling unit is located within one-half mile walking distance of public transit.
    • Accessory dwelling unit is located within an architecturally and historically significant historic district.
    • Accessory dwelling unit is part of the proposed or existing primary residence or an accessory structure.
    • When on-street parking permits are required but not offered to the occupant of the accessory dwelling unit.
    • When there is a car share vehicle located within one block of the accessory dwelling unit.
23. Multi-Family and Mixed-use Zoned Properties: Up to two new construction ADUs (either attached or detached) are permitted, and up to the number that equals 25% of the existing dwelling units may be added by converting non-livable space within existing multi-family buildings with a four-foot front and rear setback and 16-foot maximum height.
24. Sale of an ADU: An ADU cannot be sold separately from the primary residence..
25. Zoning Districts: ADUs/JADUs are allowed in residential zoning districts allowing single-family and multi-family residential uses; and where residential uses are allowed in mixed-use zoning districts, planned development districts, and specific plans.

Many cities have found loopholes around these laws and/or have adopted a local ordinance that exceeds the minimum requirements.

Contact Usto help determinewhat makes the most sense for you and your property >>

Understanding Accessory Dwelling Units and Their Importance in California

The California legislature found and declared that allowing accessory dwelling units (ADUs) in single family and multifamily zones provides additional rental housing and are an essential component in addressing housing needs in California. In 2017 and 2019, changes to ADU laws further reduced barriers, better streamline approval and expand capacity to accommodate the development of ADUs.

ADUs are a unique opportunity to address a variety of housing needs and provide affordable housing options for family members, friends, students, the elderly, in-home health care providers, the disabled, and others. Further, Accessory Dwelling Units offer an opportunity to maximize and integrate housing choices within existing neighborhoods

ADUs, inlaw suites, and garage conversions offer benefits that address common development barriers such as affordability and environmental quality. ADUs are an affordable type of home to construct in California because they do not require paying for land, major new infrastructure, structured parking, or elevators. ADUs are built with cost-effective one- or two-story prefab, modular, or wood frame construction. ADUs work very well for couples, small families, friends, young people, and seniors.

ADUs also help California meet its diverse housing needs. Young professionals and students desire to live in areas close to jobs, amenities, and schools. To address the needs of individuals or small families seeking living quarters in high opportunity areas, homeowners can construct an accessory dwelling unit, convert a garage or underutilized part of their home. This flexibility benefits not just the people living in the space, but the homeowner as well, in the form of extra monthly rent income or the ability to keep family close.

Relaxed regulations and the cost to build an ADU make it very feasible and affordable housing option for students, elderly parents, young professionals and seniors looking to downsize. The cost of an ADU typically ranges between $70k to $200k including design, permits, and construction. The price point may sound expensive upfront but an ADU is a long-term investment. Once you factor in savings on childcare, senior housing, renting an office, rental income, and increased property value it is easy to determine the return on your investment.
Accessory Dwelling Units are a powerful type of housing because they allow for different uses, and serve different populations ranging from students and young professionals to young families, people with disabilities, and senior citizens.

We Navigate the Process of Building an ADU in Your City

We currently work with these Southern California cities: Long Beach, Santa Ana, Seal Beach, Signal Hill, San Pedro, Rolling Hills Estates, Rancho Palos Verdes, Lomita, Torrance, Redondo Beach, Hawthorne, Compton, Lakewood, Norwalk, Cerritos, Los Alamitos, Cypress, Buena Park, Downey, Whittier, Los Angeles, Culver City, Santa Monica, Manhattan Beach, El Segundo, Montebello, Hacienda Heights, Fullerton, Anaheim, Garden Grove, Westminster, Fountain Valley, Yorba Linda, Placentia, Villa Park, Tustin, Orange, Irvine, Lake Forest, Laguna Beach, Huntington Beach, Costa Mesa, Newport Beach, Laguna Niguel, San Juan Capistrano, Mission Viejo, San Clemente, Rancho Santa Margarita, Alhambra, Arcadia, Pasadena, Glendale, Burbank, Encino, Calabasas.

Contact us for a Free Consultation >>