California ADU permit requirements

Exterior elevations, part of the building plans needed to verify objective standards such as height (Gov. Code §66321(b)(4)) and building-code compliance. Required for new construction; format set by the local AHJ.

CalGreen mandatory measures apply statewide to all newly constructed dwellings, so a new ADU must meet CalGreen. Conversions of existing space may have limited applicability — confirm scope with the AHJ.

All ADUs must comply with the California Building Standards Code and state building standards for dwellings (Gov. Code §66323(a)). The building/health-and-safety review is within the local agency's purview.

Dimensioned floor plans. An ADU is a new/altered dwelling reviewed against the California Building Standards Code, so floor plans are part of the building plans the agency inspects. Exact sheet requirements are set by the local AHJ.

A to-scale site plan showing property lines, setbacks, existing structures and the ADU footprint. Ministerial review inspects the application, site plan, and building plans against objective standards; the exact format is set by the local AHJ.

A newly constructed ADU is a dwelling subject to the California Energy Code (Title 24, Part 6). Newly constructed DETACHED ADUs are also subject to the solar-PV requirement (sited on the ADU or the primary dwelling); conversions/additions of existing space are exempt from solar.

Lot-coverage, FAR, open-space, front-setback and minimum-lot-size rules cannot preclude an ADU of at least 800 sq ft with 4-foot rear/side setbacks; local max-size limits must still allow ≥850 sq ft (studio/1BR) or ≥1,000 sq ft (2+ bedrooms) (Gov. Code §66321(b)).

Fire sprinklers may not be required in an ADU/JADU unless required by building standards for the existing primary residence, and building an ADU cannot trigger a sprinkler requirement for the primary residence (Gov. Code §66314(d)(12); §66323(d)).

A local agency may require no more than a 4-foot side and rear setback for a new attached/detached ADU; no setback may be required for an ADU within or replacing an existing structure (Gov. Code §66314(d)(7)).

An ADU/JADU must be approved or denied ministerially (no discretionary review, hearing, or neighbor input), judged only against objective standards, with a completeness determination in 15 business days and an approve/deny decision within 60 days — deemed approved if the agency misses it and a primary dwelling exists (Gov. Code §66317).

An ADU of 750 sq ft of interior livable space or less is exempt from local/special-district/water-corporation impact fees; above 750 sq ft, impact fees must be proportional to the primary dwelling's square footage (Gov. Code §66324). Local permit/plan-check fees are separate and set by the AHJ.

A local agency may not impose an owner-occupancy requirement on an ADU (Gov. Code §66315). Exception: a JADU that shares sanitation with the primary dwelling DOES require owner-occupancy (Gov. Code §66333(b)).

Parking may not exceed one space per ADU or per bedroom (whichever is less), may be tandem/in setbacks, and need not be replaced when a garage is converted. No parking may be required for ADUs within ½ mile walking distance of transit, conversions, historic districts, and other §66322(a) cases (Gov. Code §66314(d)(10)-(11)).

Local height limits may not be set below: 16 ft (detached); 18 ft if within ½ mile of major transit / a high-quality transit corridor or on a lot with an existing multistory multifamily dwelling; and 25 ft (or the primary-dwelling zoning limit, whichever is lower) for an attached ADU (Gov. Code §66321(b)(4)).