The City of Walnut Creek permits ADUs in the majority of residential areas, in accordance with state ADU regulations and local ordinances. Homeowners can generally build one detached ADU and one Junior ADU (JADU) per single-family lot. Multi-family buildings may also qualify for more ADUs based on site conditions.

Walnut Creek adheres to California's general ADU law but enforces its own requirements regarding fire separation, sound insulation, and design review on a site basis.

• Detached ADU: The unit is separate from the primary residence
• Attached ADU: A unit Attached to a single-family house
• Conversion ADU: converted from an existing structure on the property
• Junior ADU (JADU): A small unit up to 500 sq. ft. within an existing or new single-family home, featuring an efficiency kitchen, attached to the main residence

• Maximum Size:
  
  • Detached: 1000 square ft
  • Attached: Up to 50% of the primary home's habitable floor area, not exceeding 1,200 sq. ft
• Setbacks:
  
  • Minimum 4 feet side and backyard setbacks.
• Height Limits:
  
  • Maximum height 16 ft 
• Parking Requirements:
  
  • Additional parking is not required if the ADU is:
    
    • No additional parking spaces are required for new ADU or JADU.
    • Replacement parking is not required for parking that is converted into an ADU or JADU.

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

• Zoning and planning review: ADUs are permitted in all residential zones
• Site plan, floor plans, and elevations: Required for permit submission to show dimensions, layout, and exterior views
• Architectural and structural drawings: show construction details and structural integrity
• Title 24 energy compliance documentation: Mandatory report proving compliance with CA Energy Code

Homeowners should also review Walnut Creek’s current fee schedule, utility connection requirements, and fire code compliance..

Permit review times vary but are typically between 60 days depending on project complexity and city workload. Projects requiring corrections may take longer. Engaging professionals familiar with Walnut Creek’s ADU process can help streamline approval.

Most residential zones are eligible for ADUs, including single-family (R-1, R-2, etc.) and multi-family zones. There are no minimum lot sizes for ADUs in Walnut Creek. Some hillside or environmentally sensitive zones may have special restrictions.

For the most current and complete information, refer directly to the city of Walnut Creek.