Land-use glossary
Accessory dwelling unit
Also: ADU · Granny flat · Junior ADU · JADU
A second, smaller home on a residential lot, which state law requires cities to allow under objective standards.
An ADU is an independent living unit on the same lot as a house or apartment building: detached, attached, or converted from existing space. A junior ADU (JADU) of up to 500 square feet is created within a single-family home.
State law requires cities to approve qualifying ADUs ministerially, without a hearing, and limits the standards cities may impose. Cities still adopt local ADU ordinances to fit their codes to state law, which is when ADUs appear on council and planning commission agendas.
What to look for on the agenda
- Whether a local ordinance update is following recent state law changes
- Local standards for size, height, setbacks and parking
- Any local incentive or fee program
Recent examples in San Diego County
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Coronado · Oct 6
Second Reading and Adoption of an Ordinance Amending Section 86.56.105 Related to Accessory Dwelling Units -
Coronado · Sep 1
Introduction of an Ordinance Amending Section 86.56.105 Related to Accessory Dwelling Units -
Coronado · Aug 11
Zoning Ordinance Amendment Related to Accessory Dwelling Units
Where the rules come from: Cal. Gov. Code §66310 et seq. (ADU law, recodified in 2025). Each city's own code adds its details.
Related terms
A general explainer, not legal advice. How we work.