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Understanding California's Zoning Requirements for ADUs: A Comprehensive Guide

Accessory Dwelling Units (ADUs) have become a popular housing solution in California, providing additional living space, generating rental income, and addressing the state's housing shortage. However, before embarking on an ADU project, it’s crucial to understand the zoning requirements that apply. California has specific regulations that govern the construction and placement of ADUs, ensuring they meet safety and community standards. This blog will explore the key zoning requirements for ADUs in California, helping you navigate the regulatory landscape.


1. State Legislation Overview

California has enacted several state laws to encourage the development of ADUs. These laws include Senate Bill 13 (SB 13), Assembly Bill 68 (AB 68), Assembly Bill 881 (AB 881), and others. These laws have streamlined the approval process, reduced or eliminated certain fees, and imposed restrictions on local governments to make ADU construction more feasible.


2. Permissible Zones

ADUs are generally permitted in residential zones across California. This includes single-family and multi-family residential zones. Local jurisdictions, however, may have specific regulations and designations, so it’s essential to consult local zoning codes to determine the exact zoning requirements in your area.


3. Lot Size and Coverage

While state law does not impose minimum lot size requirements for ADUs, local governments may have regulations regarding the maximum lot coverage. This refers to the percentage of the lot that can be covered by buildings. Typically, the primary residence and the ADU combined must not exceed this limit.


4. ADU Size Requirements

California law sets specific size limits for ADUs:

  • Detached ADUs: Up to 1,200 square feet.

  • Attached ADUs: Up to 50% of the existing living area of the primary residence, with a maximum of 1,200 square feet.

  • Junior ADUs (JADUs): Up to 500 square feet.

Local jurisdictions cannot impose minimum size requirements that would preclude the construction of an ADU of at least 800 square feet.


5. Setback Requirements

Setbacks are the minimum distances that structures must be from property lines. For ADUs, California law typically requires:

  • Rear and side setbacks: At least 4 feet.

  • Front setbacks: Vary by local jurisdiction but are often the same as those required for the primary residence.

Conversions of existing structures, like garages, may have different setback requirements, often allowing for reduced or even zero setbacks if the existing structure already encroaches on the setback area.


6. Height Restrictions

Height restrictions for ADUs are generally consistent with those for the primary residence, but state law allows for a minimum height limit of 16 feet. Some local ordinances may permit taller ADUs, especially if the ADU is part of a two-story structure or built above a garage.


7. Parking Requirements

State law has simplified parking requirements for ADUs. Generally, one parking space per ADU is required. However, parking requirements are waived if:

  • The ADU is within half a mile of public transit.

  • The ADU is part of the existing primary residence or an accessory structure.

  • The ADU is in a historic district.

  • On-street parking permits are required but not offered to the ADU occupant.

  • There is a car share vehicle located within one block of the ADU.


8. Owner Occupancy

Recent legislation has removed owner occupancy requirements for newly constructed ADUs until 2025. This means that property owners do not have to live on the property where the ADU is located. However, this requirement may return in the future, so it’s important to stay updated on any legislative changes.


9. Impact Fees

Impact fees for ADUs are limited by state law. For ADUs under 750 square feet, no impact fees can be charged. For larger ADUs, fees must be proportional to the square footage of the primary residence. This has significantly reduced the financial burden on homeowners looking to build ADUs.


10. Design and Architectural Standards

Local jurisdictions may impose design and architectural standards to ensure that ADUs blend with the neighborhood's character. These standards may include:

  • Roof pitch and materials.

  • Exterior finishes and colors.

  • Window placement and design.

It’s crucial to consult local design guidelines to ensure compliance.


Conclusion

Building an ADU in California offers numerous benefits, but it’s essential to navigate the zoning requirements carefully. Understanding permissible zones, lot coverage, size, setbacks, height restrictions, parking requirements, owner occupancy, impact fees, and design standards will help ensure a smooth approval process. By staying informed and consulting with local planning departments, you can successfully add an ADU to your property, enhancing its value and functionality.

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