Accessory dwelling units are the most accessible way most California homeowners can add a unit, because state law overrides much of what cities used to block. ADUs and JADUs are not the same thing, though, and the rules keep changing. Here is the current state-law picture.
ADU vs JADU: The Core Difference
An ADU is a complete, independent dwelling — its own kitchen, bathroom, and entrance — that can be detached (a backyard cottage), attached to the house, or a conversion of existing space (like a garage). A JADU is more limited: up to 500 square feet created within the existing walls of a single-family home (often a converted bedroom), with an efficiency kitchen. A JADU may share a bathroom with the main house or have its own.
Many single-family lots can have both an ADU and a JADU under state law, which is why the two terms come up together. They are governed by overlapping but distinct rules.
State Preemption: What HCD Overrides
California's ADU laws (enforced by the Department of Housing and Community Development, HCD) override a lot of restrictive local zoning. Key state-level protections include ministerial approval (no public hearing, no CEQA), a requirement that the agency act on a complete application within about 60 days or it is deemed approved, and limits on local size, setback, and parking rules. If a city's ADU ordinance does not comply with state law (or is not properly submitted to HCD), the city must apply state ADU standards instead.
This is the central reason ADUs got easier: the state set a floor of rights that cities cannot zone below.
Size, Setbacks, and Parking (Current Rules)
Size: Local agencies must allow at least an roughly 800 sq ft ADU; statewide standards generally allow ADUs up to about 850 sq ft (or 1,000 sq ft for a unit with more than one bedroom) where a local cap would be more restrictive. Setbacks: Cities must allow at least 4-foot side and rear setbacks for a new ADU, and cannot block a conversion ADU on setback grounds. Parking: No additional parking can be required for ADUs within a half-mile of transit, within an existing structure, or in many conversion scenarios; small ADUs are exempt as well. These are state floors — a city can be more permissive, but not more restrictive than state law allows.
Exact numbers and edge cases shift as the Legislature amends the law most years, so confirm the current figures with HCD or the city for your project.
JADU Specifics and Owner-Occupancy
A JADU is capped at 500 sq ft and must be created within the existing single-family structure. It needs an efficiency kitchen and may share sanitation with the main house. The big rule to know: owner-occupancy. For ADUs, owner-occupancy requirements are now prohibited (the old sunset was removed). For JADUs, owner-occupancy may be required only where the JADU shares sanitation facilities with the primary dwelling — as of January 1, 2026, a JADU with its own private bathroom cannot trigger an owner-occupancy requirement.
JADUs also generally cannot be rented for terms shorter than 30 days (no short-term rentals), and a deed restriction is typically recorded.
What Homeowners Should Verify
Even with strong state preemption, the details matter. Confirm your lot's eligibility, the current state size/setback/parking figures, utility and sewer connection requirements, impact fees, and whether your city's ordinance is HCD-compliant. Title, HOA covenants, and lender requirements can also affect an ADU project. Because the ADU statutes change almost yearly, check the current HCD ADU Handbook and the city's planning counter before you design and budget.
The Fine Print — This Is Not Legal Advice
Brian Cooper is a licensed REALTOR® with eXp Realty, not an attorney, land-use planner, or licensed surveyor. This guide is general educational information, not legal, tax, or land-use advice, and zoning law changes often. Zoning designations, overlays, and development standards are set and interpreted by each city or county, and state housing laws are actively litigated and amended. Before you buy, build, split, or invest, verify the zoning, overlays, and development feasibility for a specific parcel with the local planning department and confirm current state law — ideally with a land-use attorney or licensed professional.
Frequently Asked Questions
What is the difference between an ADU and a JADU?
An ADU is a fully independent dwelling (its own kitchen, bath, and entrance) that can be detached, attached, or a conversion. A JADU is smaller — up to 500 sq ft created within the existing single-family home, with an efficiency kitchen, and it may share a bathroom with the main house.
How big can an ADU be in California?
Local agencies must allow at least roughly an 800 sq ft ADU, and statewide standards generally permit ADUs up to about 850 sq ft (1,000 sq ft for more than one bedroom) where a local cap would otherwise be more restrictive. Confirm current figures with HCD or your city, as the law is amended often.
Do I have to live on the property to have an ADU or JADU?
For ADUs, no — owner-occupancy requirements are now prohibited. For JADUs, owner-occupancy may be required only where the JADU shares sanitation with the main house; as of January 1, 2026 a JADU with its own private bathroom cannot trigger an owner-occupancy requirement.
How long does ADU approval take?
ADUs get ministerial approval (no public hearing), and the local agency generally must approve or deny a complete application within about 60 days, or the permit is deemed approved. Construction time is separate from approval time.
Is parking required for an ADU?
Often not. State law bars cities from requiring additional parking for ADUs within a half-mile of transit, within an existing structure, for conversions, and for small units, among other cases. Verify how the rules apply to your specific lot.
Can I rent out my ADU or JADU short-term?
Generally not for terms under 30 days. ADUs and especially JADUs typically cannot be used as short-term rentals, and a deed restriction is usually recorded. Confirm the local short-term-rental rules before planning any rental use.
