What are the California ADU rules in 2026?

As of October 2026, California law requires cities to allow ADUs of at least 850 sq ft (1,000 sq ft with more than one bedroom), caps side and rear setbacks at 4 feet, waives parking in many cases, bans owner-occupancy rules for ADUs and exempts units of 750 sq ft or less from impact fees. Qualifying ADUs are approved without a hearing.

Every rule below is stated as of October 2026. This page summarizes state law as described in the California Department of Housing and Community Development (HCD) ADU Handbook, which reflects law in effect January 1, 2026. Cities can be more generous than state law, and some local rules still apply, so treat this as the floor, not the full answer for your lot.

How big can an ADU be?

• Cities must allow at least 850 sq ft, or 1,000 sq ft for an ADU with more than one bedroom.
• Lot coverage, floor area ratio, open space and front setback rules cannot block an ADU of at least 800 sq ft with 4-foot side and rear setbacks.
• Without a compliant local ordinance, the default maximum is 1,200 sq ft for a new detached ADU and 50% of the main home for an attached ADU.
• Size is measured as interior livable space. Conversions of existing space are not subject to unit size limits.
• Junior ADUs are limited to 500 sq ft.

How close to the property line can an ADU be?

Cities cannot require more than 4 feet for side and rear setbacks. No setback applies to an ADU created inside an existing structure, or rebuilt in the same footprint. Fire and building safety rules still apply.

How tall can an ADU be?

• Detached: at least 16 feet. At least 18 feet within half a mile of a major transit stop or high-quality transit corridor, plus up to 2 feet to match the main home's roof pitch. At least 18 feet on lots with an existing multistory multifamily building.
• Attached: at least 25 feet, or the height limit for the main home, whichever is lower.
• Converted: limited to the height of the original structure.

How many ADUs can I build on my lot?

On a single-family lot, the HCD Handbook says cities must allow a combination of one ADU converted from existing space, one junior ADU and one new detached ADU, subject to the conditions in the law. On multifamily lots, cities must allow conversions of non-livable space (up to 25% of the existing units) and up to eight detached ADUs on a lot with an existing multifamily building, not exceeding the number of existing units. Your lot's specifics decide what actually fits.

When is parking not required for an ADU?

Cities cannot require parking for an ADU that is:

• within half a mile walking distance of public transit
• in an architecturally and historically significant historic district
• part of the existing home or an existing accessory structure
• in an area that requires on-street parking permits not offered to the ADU occupant
• within one block of a car share vehicle

Where parking is allowed to be required, it is capped at one space per unit or bedroom, whichever is less. Parking lost when a garage or carport is converted or demolished for an ADU does not have to be replaced.

Do I have to live on the property?

Not for an ADU. Under AB 976, cities cannot impose owner-occupancy requirements on ADUs. The exception is an ADU sold separately to a qualified buyer under the state's nonprofit sale provisions. For a junior ADU, a city can require the owner to live on site only if the JADU shares sanitation facilities with the main home.

What impact fees apply to an ADU?

ADUs of 750 sq ft or less of interior livable space are exempt from impact fees. Larger ADUs can be charged in proportion to the main home's square footage. Junior ADUs of 500 sq ft or less are exempt. ADUs within existing space and JADUs are generally not treated as new residential uses for utility connection fees, unless built with a new single-family home. Permit and plan-check fees still apply.

What are the junior ADU rules?

• Up to 500 sq ft, entirely within a single-family home (an attached garage counts).
• One per single-family lot; not allowed on multifamily sites or in detached structures.
• An efficiency kitchen is required; the bathroom can be shared or separate.
• No parking can be required.
• Rentals must be longer than 30 days.

More detail on our junior ADU page.

Can I rent out an ADU on Airbnb?

For a junior ADU, no: state law requires rentals longer than 30 days. The HCD Handbook also says rentals of ADUs created under the state's guaranteed-unit provisions must be for terms longer than 30 days, and cities may require the same for other ADUs. Check your city's short-term rental rules before planning around nightly rentals.

Can I sell my ADU separately?

Only where your city allows it. AB 1033 lets a city or county adopt an ordinance allowing an ADU and the main home to be sold separately as condominiums. It is a local opt-in, not a statewide right. Apart from a narrow exception for certain nonprofit sales to qualified buyers, an ADU cannot be sold separately unless your city has adopted such an ordinance. Ask your city, or us, whether one is in effect where you live.

How fast must the city review an ADU permit?

Qualifying ADUs are approved ministerially, without a hearing. The city has 15 business days to determine whether an application is complete and 60 days from a complete application to approve or deny it, when a home already exists on the lot. Full detail in do I need a permit to build an ADU.

What changed in ADU law for 2026?

Bills passed in 2025, including SB 543 and AB 1154, took effect for 2026. As summarized by HCD, changes include measuring size by interior livable space, the 15-business-day completeness check, impact fee thresholds of 750 sq ft for ADUs and 500 sq ft for JADUs, tying JADU owner occupancy to a shared bathroom, a minimum rental term longer than 30 days for JADUs, and a 60-day review period in the coastal zone.