California ADU Rules & Size Limits (2026)

Short answer: Under California state ADU law (as of 2026), your city must allow a detached or attached ADU of at least 850 sq ft (studio or 1-bedroom) or 1,000 sq ft (2+ bedrooms), with 4-foot side and rear setbacks and up to 16 feet in height (18 feet near major transit). A separate statewide rule guarantees you can build a detached ADU of at least 800 sq ft. A junior ADU (JADU) can be up to 500 sq ft inside your existing home. Owner-occupancy is no longer required for ADUs, and most single-family lots can add one ADU plus one JADU.

California ADU rules at a glance

Rule	ADU	Junior ADU (JADU)
Maximum size	850 sq ft (studio/1BR) or 1,000 sq ft (2+BR); at least 800 sq ft guaranteed for a detached unit	500 sq ft, within the existing home
Side & rear setbacks	4 feet	Uses the existing home’s walls
Maximum height	16 ft (18 ft near major transit; 25 ft for attached)	N/A (inside the home)
Owner-occupancy	Not required	Required only if it shares a bathroom with the main home
Parking	Up to 1 space; none required within ½ mile of transit	None required

Size limits

Cities must permit a detached or attached ADU of at least 850 sq ft for a studio or one-bedroom, and 1,000 sq ft for two or more bedrooms. Many Los Angeles-area cities allow up to 1,200 sq ft. A garage or interior conversion is limited to the existing structure, plus up to 150 sq ft for entry and exit. A JADU is capped at 500 sq ft and must be built within the walls of the existing home.

Setbacks and height

New detached ADUs need only 4-foot side and rear setbacks. There is no state-required front setback (local rules apply). Height is capped at 16 feet on a standard single-family lot, 18 feet near major transit or on multifamily lots, and 25 feet (or the main home’s height) for an attached ADU.

Owner-occupancy and parking

You no longer have to live on the property to build an ADU in California. A JADU requires owner-occupancy only if it shares sanitation facilities with the main home. Cities may require at most one parking space per ADU, and no parking is required when the lot is within a half-mile of transit, when the ADU is a conversion, or in several other cases. Cities cannot require replacement parking when a garage is converted.

How many ADUs can you build?

On a typical single-family lot you can generally add one ADU and one junior ADU in addition to your primary home. Rules for multifamily properties differ and allow more units.

These reflect California state law as of 2026. Individual cities may have additional standards — confirm the details for your property with your city or with our team.

Frequently asked questions

What is the maximum ADU size in California?

Cities must allow at least 850 sq ft for a studio or one-bedroom ADU and 1,000 sq ft for a two-plus-bedroom ADU. A detached ADU of at least 800 sq ft is guaranteed statewide, and many cities allow up to 1,200 sq ft.

Do I need to live on the property to build an ADU?

No. Owner-occupancy is no longer required for ADUs in California. A junior ADU only requires owner-occupancy if it shares a bathroom with the main home.

How close to the property line can an ADU be?

A new detached ADU needs only 4-foot side and rear setbacks under California law.

Do I need parking for an ADU?

At most one space per ADU, and no parking is required if the property is within a half-mile of transit or the ADU is a garage or interior conversion.

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