Accessory Dwelling Unit (ADU)?

An accessory dwelling unit (ADU) is a legal and regulatory term for a secondary house or apartment that shares the building lot of a larger, primary home. The unit cannot be bought or sold separately, but they are often used to provide additional income through rent or to house a family member. For example, an elderly parent could live in a small unit and avoid having to move to an assisted living facility.

What is an ADU?

An ADU is an accessory dwelling unit with complete independent living facilities for one or more persons and has a few variations:


The unit is separated from the primary structure.


The unit is attached to the primary structure.

Converted Existing Space

Space on the lot of the primary residence that is converted into an independent living unit.

Junior Accessory Dwelling Unit (JADU)

A specific type of conversion of existing space that is contained entirely within an existing or proposed single-family residence

ADU Laws

A statewide exemption ADU is an ADU of up to 800 square feet, 16 feet in height, as potentially limited by a local agency, and with 4 feet side and rear yard setbacks. ADU law requires that no lot coverage, floor area ratio, open space, or minimum lot size will preclude the construction of a statewide exemption ADU.

5 things you must know about the ADU laws

CA wants you to build housing

California has a long way to go before solving our housing crisis but they also understand where to start. It's by allowing more housing to be built. Hence the new ADU updates. Learn more...

Streamline Approval

Once a "completed" application is submitted, the local jurisdiction has 60 days to decision the permit application. Learn more...

Size does Matter

There's a difference between what you can do and what you should do. ADUs are meant to cost you sell than building an entirely brand new home from the ground up. In order to avoid most traditional impact fees the size of your ADU should be below 750 square feet. That's the sweet spot. Learn more...

Owner occupancy requirements

At some point you had to be living on site in order to qualify for the new ADU laws. But that is not the case anymore. Every California home can have up to 2 ADUs regardless of where the property owner actually lives. Learn more...

Legalizing existing non permitted ADUs

This might be the best law change to come out of the December 2020 ADU updates. Local agencies must delay enforcement against a qualifying substandard ADU for 5 years! As long as the Violation is not a health and safety issue. Get that ADU legalized.

What Is an ADU in Real Estate?

It is any home that has an additional self-contained living space on the property. The terms for ADUs vary widely from location to location, and by type of ADU.

Some terms used to describe accessory dwelling units are the following:

  • In-law suite
  • In-law apartment
  • Granny unit
  • Carriage house
  • Tiny home
  • Casita
About Images

In-law suite

An in-law suite is a separate dwelling space in your primary residence or on your property. They’re sometimes referred to as granny flats or secondary units. Generally, people build in-law suites to allow their aging parents or in-laws to live with them while still ensuring a private place to retreat to. Learn more..

In-law apartment

When your in-laws come to visit, where did they stay? If they came to live with you, would they enjoy living in that same space? For most homeowners, the answer is no. Learn more..

Granny unit

A granny flat is a small house built on an existing property. It has its own entrance, kitchen, bathroom and living space. Learn more..

Carriage house

A carriage house is an outbuilding near a larger home that was initially built to store horse-drawn carriages and sometimes housed the coachman or caretaker on the upper floor. In contemporary society, homeowners often repurpose these buildings into small second homes or garage apartments , tiny houses, guest houses, detached garages, home offices, studio spaces, or in-law suites. Learn more..

Tiny home

Tiny houses usually have a kitchen, a bathroom, some sort of living space, and a lofted bed. Most people need to hook up to a utilities outlet to have electricity, but there are also self-sustainable houses. Taking advantage of renewable resources like solar power, tiny homes are living up to the expectation of going green. Learn more..


Casita means cottage in Spanish. More formally, a Casita by definition is a small self-contained dwelling, typically unattached from a main home, but on the same property. Learn more..