What is an Accessory Dwelling Unit (ADU) ?

An ADU is an additional dwelling unit  that can be attached or detached from the primary dwelling.

 The ADU could provide affordable housing options for family members, friends, students, the elderly, in-home health care providers, the disabled, and others.

You may want to consider taking advantage of the change in California State law which made it easier to add a second house, called an Accessory Dwelling Unit (ADU), to your residential zoned property.

Granny flat, in-law suite, accessory dwelling unit (ADU), converted garage, backyard cottage, basement apartment , companion units – accessory dwelling units go by many names, but are always a self-contained home smaller than the main house and legally part of the same property. ADU’s can take many forms and vary in size, but always contain everything someone needs to live, including a kitchen, bathroom and place to sleep. ADU’s typically range from 400 sf  to 1200 sf.

Where is an ADU allowed?

An ADU can be located on residentially zoned property that has an existing single-family residence. For a complete list of ADU requirements, please click here.

Is a Building Permit Required for an ADU?

Yes, you will be required to obtain a Building Permit to ensure that the new house meets all the zoning, building, health & safety codes.

What Size ADU is Allowed? How Big?

An ADU is intended to be secondary in size to the single-family residence.  California State Laws  says    an  ADU can be attached  to or detached from  the  primary dwelling  and may be up to 50% of the size of the single-family residence, up to a maximum of 1,200 square feet.. Check local ADU regulations as some cities  within San Diego County have   adopted other requirements

Why Install   an Accessory Dwelling Unit?

People build ADU’s for lots of reasons, but the most common are rental income and/or to house relatives. Having a second unit is a simple and old idea to convert unused space. Second units are a relatively affordable type of construction, because they do not require purchasing land or major new infrastructure. 

With rents for a 1 bedroom typically averaging over $1400 / month in many areas of San Diego County many people install  an ADU to help pay off their primary mortgage or earn extra income.


Can you use extra income or do you have a family member /friend that needs a place to live?

How Much Does it Cost to Install  an ADU?

Cost depends on several factors:

ADU size

Accessibility to ADU location

Building Code (Local or Federal)

Local Building department requirements and Fees

USModular    offers detached ADU’s starting at $89,000 for the ADU built to Federal Code, Delivery, Foundation, and Utility Connection to cities within  San Diego County.


Community Benefits of   installing an ADU

ADU’s can help address the housing challenges in San Diego County by adding homes that are generally more affordable, which helps provide workforce housing and preserves diversity and community character. Many homeowners are motivated to build a second unit to rent to a school teacher, firefighter or other community member who might otherwise have to commute a long distance to find a home they can afford.

Contact us at 888-987-6638 or sandiegoaccessorydwellingunits.com for more info

San Diego County ADU Regulations

In an effort to combat rising housing costs California passed major legislation allowing any house zoned for single-family to build a second rentable unit, known as an accessory dwelling unit. This has opened up massive opportunities for California homeowners allowing them maximize their property values. If you’re interested in building an accessory dwelling unit, you’ve come to the right place! Explore all the ADU regulations for San Diego County.