California ADU Regulations

San Diego California ADU Regulations in 2024

What is all the buzz about ADUs in San Diego?

What is an ADU?

An ADU is an Accessory Dwelling Unit aka Granny Flat aka a small home that can be built in your backyard and used for extended family, friends, or as a rental property.

It can be attached or detached from the main house.

The State of California is leading the nation in ADU development and regulations, and a great summary can be seen in the ADU handbook published by the State of California:

 One of the most affordable types of ADUs is a prefabricated home. One of San Diegos most active prefabricated ADUs builders in San Diego is USModular Inc.  “ADUs are becoming very popular for homeowners looking to generate rental income in their backyard or for families that have children or elderly parents moving home, as it gives everybody their own space, is affordable, and ADU the value of the property,” says Todd Kessler, CEO of USModular Inc. (

Some of the highlights of the State of California ADU regulations include:

  • Every residential property in California is allowed to have one ADU of up to 800 sq ft regardless of lot size, floor area ratio, or main residence size.
  • This ADU can be up to 16 feet in height.
  • Homeowners are to build one attached ADU, one detached ADU, and one JADU all on the same property.
  • Cities must allow at least 850 square feet for one-bedroom ADUs and at least 1,000 if the ADU has two or more bedrooms. Cities cannot impose smaller maximum sizes, but they can impose larger ones.  Every city has specific regulations for size and bedroom count above 800.
  • Setbacks: Most cities have side yard and rear yard setbacks at 4′, but there are some cities that allow 0’ setbacks, and some areas have fire department regulations that require 5’ setbacks. The bottom line is side and rear yard setbacks are much smaller now for ADUs.
  • Parking: Most cities want to see 1 off-street parking space on your property for the ADU, except when your home is located within ½ mile of public transit
  • Fire sprinklers are required if the main house has them or if ADU is not close to a fire hydrant.
  • Multifamily properties are allowed multiple ADUs  
  • Solar panels are not required for prefabricated ADUs but may be required on a site-built ADU
  • Condo your ADU: This is a new State of California law, and when adopted by cities, you will be allowed to sell your ADU as a separate unit.

The City of San Diego ADU regulations are the most progressive in State of California!

Beyond the State of California-mandated ADU regulations, San Diego will allow multiple ADUs in specific transit districts and will also allow Tiny Homes as ADUs.

 San Diego has a Population of  1,419,845

  Median property value: $ 622,300
Single-family properties: 287,927

Persons per household: 2.68
Median rental value: $ 2,779
Multi-family properties: 246,462

Based on the San Diego population, a number of Single-Family Homes, Multifamily Properties, and Rental values, there is a lot of opportunity for ADU construction in San Diego.

 City of San Diego ADU regulations:

What is prefabricated construction?

Prefabricated construction means homes are built off-site in a factory, just like your car and the majority of every other item you use in your daily life.  Prefabricated homes are also known as Manufactured Homes and Modular Homes.  Prefabricated home plans are pre-approved by the State of California. These homes are designed, reviewed, approved, and inspected by the State of California.     The main benefits of prefabricated homes are that they are less costly, faster to build in a factory, and have less impact on homeowners and neighbors. USModular Inc. is a premier contractor of prefabricated homes with over 40 years of experience in the industry.  You can see the available floor plan and pricing at