Navigating Local vs. State Regulations for ADUs in California

 Table of Content
 1. What is an ADU?
2. Benefits of Building a Permitted ADU in California
 3. Understanding State vs. Local ADU Regulations in California
3.1 California State ADU Laws (High-Level Overview)
3.2 Local Regulations and Why They Still Matter
 4. Local Regulations and Why They Still Matter
 5. FAQ
Accessory Dwelling Unit

What is an ADU?

An Accessory Dwelling Unit (ADU) is a secondary housing unit located on the same lot as a single-family or multi-family residence. Often referred to as granny flats, in-law units, backyard homes, or secondary suites, ADUs can be attached, detached, or converted from existing structures like garages or basements. ADUs are gaining popularity across California as a solution to the housing crisis, offering flexible living arrangements and additional rental income for homeowners.

Benefits of Building a Permitted ADU in California

Building a permitted ADU in California offers several key advantages:

  • Legal Rental Income: Permitted ADUs can be legally rented, providing homeowners with a stable source of income.

  • Property Value Increase: A well-designed and legally approved ADU can significantly boost property value.

  • Multigenerational Living: ADUs provide private, independent living spaces for aging parents, adult children, or caregivers.

  • Sustainability: Small, energy-efficient units reduce environmental impact and promote sustainable urban development.

  • Housing Flexibility: ADUs offer versatile use, from home offices to guest houses or short-term rentals (where allowed).


Understanding State vs. Local ADU Regulations in California

California has enacted statewide ADU laws to streamline the development process, but local jurisdictions still play a role in shaping specific implementation rules. Homeowners must navigate both layers of regulation to ensure compliance.


California State ADU Laws (High-Level Overview)

The California legislature passed several laws (e.g., AB 68, AB 881, SB 13) that:

  • Limit local restrictions: Cities and counties cannot impose excessive lot size, parking, or setback requirements.

  • Expedite approvals: Jurisdictions must approve or deny ADU applications within 60 days.

  • Eliminate impact fees: No impact fees for ADUs under 750 square feet.

  • Allow multiple ADUs: Up to two ADUs (one junior and one detached) may be allowed on single-family lots.

These laws were designed to override restrictive local ordinances that previously hindered ADU development.


Local Regulations and Why They Still Matter

While state law sets the foundation, local governments can tailor certain aspects, including:

  • Design standards: Materials, rooflines, and exterior finishes may need to match the primary home.

  • Historic preservation: Homes in historic districts may face additional review or design limitations.

  • Height limits and setbacks: Cities can set reasonable development standards as long as they don’t conflict with state law.

  • Owner-occupancy rules: Some cities still require the owner to live on the property (especially for Junior ADUs).

  • Short-term rentals: ADU use as an Airbnb or vacation rental may be restricted or banned locally.

It's crucial to check your local planning or building department’s ADU ordinance to avoid delays or denials.


Check How to Get an ADU Permit in California


How to Navigate Local and State ADU Regulations

To build a successful ADU project in California, follow these steps:

  1. Start with State Law: Understand your rights under California’s ADU laws. Know what’s allowed statewide.

  2. Check Local Ordinances: Review your city or county’s ADU-specific requirements on setbacks, height, parking, and design.

  3. Consult with a Professional: Work with a designer, architect, or ADU consultant familiar with both local and state compliance.

  4. Submit a Complete Application: Include site plans, floor plans, and any required reports (e.g., fire, sewer).

  5. Stay Informed: Laws change. Stay updated on new bills or local amendments that may affect your project.

FAQ

Can I build an ADU on my single-family property in California?

Yes, most single-family lots in California are eligible to build at least one ADU and one Junior ADU, thanks to recent state laws.

Do I need a permit to build an ADU?

Absolutely. All ADUs require a permit from your local jurisdiction to be legal, rentable, and insurable.

How long does it take to get ADU approval?

By law, your local city or county must approve or deny your ADU application within 60 days of receiving a complete application.

Can my city stop me from building an ADU?

Cities must allow ADUs under state law, but they can still regulate aspects like design, setbacks, and height—as long as they don’t make building unreasonably difficult.

Are there different rules for detached and attached ADUs?

Yes. Detached ADUs often have more flexibility in size and placement, while attached ADUs must share a wall with the main residence and follow stricter design alignment.

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ADU Permit Process
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