In 2026, California building regulations for Accessory Dwelling Units (ADUs) and Junior ADUs (JADUs) prioritize streamlined permitting and the removal of common barriers to construction.
Key Size and Height Regulations
- Maximum ADU Size: Detached ADUs can typically be up to 1,200 sq. ft. statewide. Attached ADUs are generally limited to 50% of the primary residence’s living area, with a cap of 1,200 sq. ft..
- Minimum ADU Size: Units must have a minimum of 150 sq. ft. of “interior livable space”.
- JADU Limit: Junior units must be contained within the existing or proposed primary home and cannot exceed 500 sq. ft..
- Height Limits: Detached ADUs are typically allowed up to 16 feet. However, specific laws can allow heights up to 18 feet (near transit or for multifamily lots) or even 25 feet for attached units or those built above detached garages.
Setbacks and Placement
- Standard Setbacks: For new detached ADUs, a minimum of 4-foot side and rear setbacks is required.
- Conversion Exemptions: If you convert a legal, existing structure like a garage, no new setbacks are required, even if it is currently on the property line.
- Front-Yard Waivers: Local agencies cannot use front-yard setback requirements to prevent an ADU of at least 800 sq. ft. from being built.
Permitting and Fee Exemptions
- Streamlined Approval: Local agencies must ministerially approve or deny a complete ADU application within 60 days; if no action is taken, the application is often deemed approved.
- Impact Fee Waivers:
- Development Impact Fees: Waived for all ADUs under 750 sq. ft..
- School Impact Fees: As of January 1, 2026, ADUs and JADUs under 500 sq. ft. of interior livable space are exempt from school impact fees.
- Pre-Approved Plans: By 2025, all California cities were required to offer pre-approved ADU plans to help homeowners bypass custom design delays.
Occupancy and Parking
- No Owner-Occupancy: For standard ADUs permitted after January 1, 2025, owners are not required to live on the property; both the main house and ADU can be rented out. JADUs typically still require owner occupancy of one of the units.
- Parking Exemptions: No off-street parking is required for an ADU if it is within half a mile of public transit, located in a historic district, or part of an existing structure.
- Rental Terms: All ADUs must be rented for a term of at least 30 days; short-term rentals (like Airbnb) are generally prohibited.
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