Los Angeles County Planning defines an Accessory Dwelling Unit (ADU) as a residential unit with a full kitchen and bathroom that is accessory to a primary residential use, such as a single-family home or multifamily building. County guidance explains that an ADU may be detached, attached, or located within existing structures, and it must provide independent living facilities, including permanent provisions for cooking, sleeping, and sanitation. Planning materials emphasize that ADUs can be built on properties with a house or an apartment building and may be used as rental housing or as accommodation for family or caregivers on the same lot.
The County also recognizes Junior Accessory Dwelling Units (JADUs), which are similar in concept but more limited in size and configuration. According to Los Angeles County Planning, a JADU has a maximum size of 500 square feet, must be wholly contained within the main home, and must have its own exterior access. JADUs may share some infrastructure, and in practice often have more constrained kitchen configurations compared to full ADUs, consistent with statewide JADU standards in California’s Government Code.
State-level guidance, summarized in industry explainers on California ADU law, notes that most full ADUs are allowed in the 800–1,200 square foot range and must include an independent entry and complete kitchen and bath facilities to qualify. County materials also highlight that professional architects have developed pre-approved plans for different ADU types and sizes, reinforcing that the County treats ADUs as full, code-compliant dwelling units rather than informal additions. This regulatory framing affects building code compliance, permitting, utility connections, and eligibility for rental use.