The City of Clayton allows Accessory Dwelling Units (ADUs) and Junior Accessory Dwelling Units (JADUs) to comply with statutory requirements of California law. These regulations apply to most residential zones and are designed to support the construction of additional dwelling units while following state ADU legislation.

• Detached ADU: A separate, single-unit residential unit.
• Attached ADU:  Created by converting existing areas of the primary dwelling or accessory structures (e.g., garages) into an independent living unit.
• Conversion ADU: Created by converting existing areas of the primary dwelling or accessory structures into an independent living unit.
• Junior ADU (JADU): It is no more than 500 square feet in size.

• Maximum Size:
  
  • Detached: Up to 1,200 square feet
  • Attached: Up to 50% of the primary dwelling’s floor area, not exceeding 1,200 sq ft
• Setbacks:
  
  • The side- and rear-yard setbacks are at least 4 feet.
• Height Limits:
  
  • Detached: Up to 18 feet
  • Attached: Maximum 25 feet in height.
• Parking Requirements:
  
  • Additional parking is not required if the ADU is:
    
    • located within one-half mile walking distance of public transit
    • existing primary residence or an accessory structure 
    • located within an architecturally and historically significant historic district

To build an ADU in Clayton, the following approvals are typically required:

• Zoning compliance review: Confirm that your property is zoned to allow an ADU / JADU
• Site plan and elevations: showing property lines, existing structures, proposed ADU, setbacks, utilities, and driveways
• Architectural drawings: including floor plans, elevations, roof plan, and cross-sections
• Structural calculations and engineering if applicable
• Title 24 energy documentation: compliance with California energy standards
• Permit submission through the City of Clayton’s online portal
  

Homeowners should also review Clayton current fee schedule, utility connection requirements, and fire code compliance.

Permit review times vary but are typically between 6 to 12 weeks, depending on project complexity and city workload. Projects requiring corrections or additional documentation may take longer. Engaging professionals familiar with Clayton’s ADU process can help streamline approval

Most residential zones are eligible for ADUs, including R-1 zones. There are no minimum lot sizes for ADUs in most areas of Clayton. Some hillside or environmentally sensitive zones may have special restrictions.

For the most current and complete information, refer directly to the City of Clayton.