Are ADUs Legal in California? Comprehensive Guide

Are ADUs Legal in California? Comprehensive Guide

Accessory Dwelling Units (ADUs) have become increasingly popular in California as a potential solution to the state’s housing crisis. 

These secondary living spaces, built on the same lot as a primary residence, offer additional housing options for homeowners and renters. 

ADUs Legal

before starting an ADU project, it’s essential to understand the legality of these units in California.

What is an ADU?

An Accessory Dwelling Unit, also known as a granny flat, an in-law unit, or a backyard cottage, is a self-contained living space attached to or detached from the primary residence. 

ADUs typically include a bedroom, bathroom, kitchen, and living area and can be created through:

  • New Construction
  • Conversion of existing space
  • Addition to an existing structure
ADUs Legal

California’s ADUs Legal

In recent years, California has taken significant steps to encourage the development of ADUs to address the state’s housing shortage. 

The state legislature passed a series of bills in 2017 that made it easier for homeowners to build ADUs by reducing regulatory barriers and streamlining the approval process.

Under current California law:

– ADUs are allowed in all residential zones

– Cities and counties must approve ADUs that meet specific size and design requirements

– ADUs can be built concurrently with a primary residence

– Parking requirements for ADUs are limited

Local Zoning and Regulations

While California state law has made it easier to build ADUs, it’s crucial to check with your local city or county planning department to understand any additional zoning regulations or requirements. 

Some cities may have more restrictive ordinances, such as limits on ADU size or design standards.

For example, in the City of Los Angeles:

1. ADUs must be located on a lot with an existing single-family residence

2. ADUs cannot exceed 1,200 square feet or 50% of the primary residence’s living area

3. ADUs must meet setback and height requirements

ADUs Legal

Permitting and Building Requirements

To legally build an ADU in California, homeowners must obtain the necessary permits from their local building department. 

This typically involves submitting plans, paying fees, and undergoing inspections to ensure the ADU meets all applicable building codes and standards.

Some critical considerations for ADU permitting and construction include:

– ADUs must be built to the same building code standards as the primary residence

– Utility connections for water, sewer, and electricity must be installed appropriately

– Fire safety requirements, such as smoke detectors and egress windows, must be met

Benefits of Building an ADU in California

Building an ADU can provide numerous benefits for California homeowners, such as:

1. Providing housing for family members or generating rental income

2. Increasing property value and equity

3. Contributing to the state’s housing supply and affordability

Challenges and Considerations

While ADUs offer many advantages, there are also potential challenges and considerations. 

Construction costs can be significant, ranging from $100,000 to $400,000. 

Financing options may be limited, as not all lenders offer ADU-specific loans. Additionally, homeowners are responsible for ongoing maintenance, repairs, and landlord duties if renting the ADU.

ADUs Legal

Resources for ADU Builders in California

Homeowners interested in building an ADU in California can access various resources to help navigate the process. 

The California Department of Housing and Community Development provides an ADU Handbook and other informational materials. 

Local city and county planning departments offer guidance on zoning and permitting requirements.

Professional organizations, such as the American Institute of Architects and the National Association of Home Builders, provide educational resources and directories of qualified professionals.


ADUs are legal in California and offer a promising solution to the state’s housing challenges. 

Homeowners can decide whether an ADU suits their property by understanding the state and local regulations governing ADUs and the potential benefits and challenges. 

With careful planning and execution, an ADU can provide valuable housing options and enhance the value of a home for years to come.

ADUs Legal

Frequently Asked Questions (FAQs)

Can I build an ADU on my property if I have a multi-family residence?

ADUs are usually only allowed on properties with single-family residences. However, some cities may allow them on multifamily properties under certain conditions.

Do I need to provide additional parking for my ADU?

In many cases, no additional parking is required for ADUs. However, local regulations may vary, so you must check with your city or county planning department.

Can I sell my ADU separately from my primary residence?

No, ADUs cannot be sold separately from the primary residence. They are considered an accessory to the main dwelling and must be sold with the primary property

How long does it take to get permits and build an ADU?

An ADU’s permitting and construction process can vary depending on local regulations and the project’s complexity. On average, completing an ADU can take anywhere from a few months to a year or more.

Are there any financial assistance programs available for building ADUs?

Some cities and counties offer financial incentives or assistance programs for ADU construction, such as reduced permit fees or low-interest loans. Check with your local government or housing department for available programs.

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