What You Need to Know About ADUs in 2020

Laura Blair


Accessory Dwelling Units or “ADUs” have been discussed a lot this year because the state of California enacted several laws that intend to address the state’s housing crisis by easing many restrictions on the building of ADUs. Here is a quick summary of the most relevant changes for CMA members.


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:

  • Detached: The unit is separated from the primary structure.
  • Attached: The unit is attached to the primary structure.
  • Converted Existing Space: Space (e.g., master bedroom, attached garage, storage area, or similar use, or an accessory structure) 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.



First Big Change: Some ADUS Have to Be Automatically Approved

The state mandated that cities must permit certain categories of ADU without applying any local development standards (e.g., limits on lot size, unit size, parking, height, setbacks, landscaping, or aesthetics), if proposed on a lot developed with one single-family home. ADUs eligible for this automatic approval include:

  • An ADU converted from existing space in the home or another structure (e.g., a garage), so long as the ADU can be accessed from the exterior and has setbacks sufficient for fire safety.
  • A new detached ADU that is no larger than 800 sq. ft., has a maximum height of 16 feet, and has rear and side setbacks of 4 feet.
  • Both of the above (creating two ADUs), if the converted ADU is smaller than 500 sq. ft.



Second Big Change: Some ADUs only subject to Limited Review

Even if not subject to automatic approval, a city generally must approve any attached or detached ADU under 1,200 sq. ft. unless the city adopts a new ADU ordinance setting local development standards for ADUs. If a city adopts such an ordinance, it must abide by the following restrictions:

  • No minimum lot size requirements.
  • No maximum unit size limit under 850 sq. ft. (or 1,000 sqft for a two-bedroom ADU).
  • No required replacement parking when a parking garage is converted into an ADU.
  • No required parking for an ADU created through the conversion of existing space or located within a half-mile walking distance of a bus stop or transit station.
  • If the city imposes a floor area ratio limitation or similar rule, the limit must be designed to allow the development of at least one 800 sq. ft. attached or detached ADU on every lot.


What does this mean for Multifamily Units?

  • Cities must permit these types of units in multifamily buildings without applying any local development standards:
    • New units within the existing nonliving space of a building (e.g., storage rooms, basements, or garages). At least one unit and up to ¼ of the existing unit count may be created this way.
    • Two new homes on the same lot as the multifamily building but detached from it, with 4-foot side and rear setbacks and a 16-foot maximum height.

What About Parking?

  • Parking requirements for ADUs are still one parking space per unit or per bedroom (whichever is less) if you are located more than half a mile from public transit.
  • ADUs do not require parking if they are created within an existing space in your house or an accessory structure, like a garage or carport.
  • No replacement parking is required for the main residence when a garage or carport is demolished or converted to create an ADU.

What about setbacks?

  • Setbacks for new ADUs have been reduced to 4 ft. for side and rear yards.
  • If you have a garage or carport you want to convert, but determine it is more costly to repair the old structure than it is to replace it. New state law permits you to remove an existing structure and replace it with a new ADU that matches its footprint, maintaining the existing reduced setbacks.

These changes make it possible for developers to increase their unit count and increase density. In most cases, ADUs will still need planning approval and all ADUs will need a building permit in order for the construction to begin. BuildZig offers site assessments, entitlements and funds control services for ADUs and other projects. Contact lblair@buildzig.com for more information.



Laura oversees the funds control depart and all Buildzig transactions – including property acquisitions.