In 2020, it became easier than ever to build Accessory Dwelling Units in California, thanks to changes in state ADU law. These bills invalidated local ADU ordinances across the state and replaced them with state-mandated rules.
Since 2017, California cities have been required to allow the owners of most single-family homes to add accessory dwelling units (ADUs) or ‘in-law units’ to their properties. Cities have been slow to comply with this rule, despite universal support for ADUs from neighborhood groups, affordable housing organizations, and residents testifying at public meetings.
The key highlights of the new state ADU law are summarized below.
Reduced Costs and Burdens for Developing ADUs
- ADU applications must be approved within 60 days, without a hearing or discretionary review
- For ADUs permitted by 2025, cities/counties cannot require the owner to live at the property
- No impact fees are required for ADUs under 750 sqft; proportional fees apply to larger ADUs
- An ADU can be developed at the same time as a primary dwelling, with no additional hearing
- A city/county must delay code enforcement on an unpermitted ADU to allow it to be legalized
- Single-family HOAs must allow development of ADUs, subject to reasonable standards
- Single-family homeowners can also develop JADUs—units under 500 sqft within a residence
ADUs Subject to Automatic Approval — No Local Limits
Cities/counties must permit certain categories of ADUs without applying any local development standards, if proposed on a single-family lot. ADUs eligible for this automatic approval include:
• An ADU or JADU converted from existing space in the home or another structure (e.g., a garage), so long as the ADU has exterior access and setbacks sufficient for fire safety
• A new detached ADU under 800 sqft in size, 16 feet in height, with 4-foot side/rear setbacks
• Multiple of the above options to create one internal JADU and an internal or detached ADU
ADUs Subject to Ministerial Approval — Minimal Local Limits
Cities/counties must generally approve attached or detached ADUs under 1,200 sqft unless they adopt local development standards. If adopted, local standards have the following limitations:
• No minimum lot size requirement
• No maximum unit size limit less than 1,000 sqft for a two-bedroom ADU
• No requirement for 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 other public transit
• No height limit under 16 feet or side/rear setback requirements over 4 feet
• No setback requirements for conversions/replacements of existing legal structures
• Design standards must be objective and are assessed by staff, not elected officials
• FAR and similar restrictions must be relaxed to allow development of an 800 sqft ADU
Adding Units to Multifamily Properties
The following types of residential units can be added to multifamily buildings, with no local limits:
• New units within the existing non-living space of a building (storage rooms, basements, garages, etc.), with one new internal unit allowed for every four existing units
• Two new detached homes, with 4-foot side/rear setbacks, up to 16 feet in height
The Housing Accountability Act requires cities to use specific, objective criteria when they assess applications to build zoning-compliant housing development projects. For affordable housing projects, even stricter rules apply. The Legislature recently gave organizations like Californians for Homeownership an automatic right to sue to obtain approval of a project, without any participation by the applicant.