The City of San Carlos permits ADUs across most residential zones. San Carlos follows both state and local ADU laws, allowing most single-family homes to build one detached ADU and one Junior ADU (JADU) per lot. Multi-family properties may be eligible for multiple ADUs, depending on site conditions.

San Carlos aligns with California’s broader ADU legislation but has its own requirements for height, setbacks, and design review.

• Detached ADU: A newly constructed, separate residential unit on the same lot as the primary dwelling.
• Attached ADU: A unit that is part of an existing or proposed single-unit dwelling.
• Conversion ADU: A unit created by converting existing space within the primary dwelling, such as a garage or storage area.
• Junior ADU (JADU): Up to 500 sq ft, created within the existing living area of the primary home, with an efficiency kitchen, and requires owner-occupancy.

• Maximum Size:
  
  • Detached: Up to 1,200 sq ft
  • Attached: Up to 50% of the primary dwelling’s existing floor area, not exceeding 1,200 sq ft
• Setbacks:
  
  • Minimum 4 ft from side and rear property lines
• Height Limits:
  
  • Detached:  Typically, 16 ft
  • Attached: Up to 25 ft, depending on location and compliance with the primary home's roof pitch
• Parking Requirements:
  
  • Additional parking is not required if the ADU is:
    
    • Junior ADU (JADU) (under 500 sq. ft within the existing home)
    •  Located within half a mile of public transit
    •  Converted from an existing structure (e.g., garage, storage shed)
    •  Part of the existing primary residence
    •  Located in a historic district or designated area
    •  When a garage or covered parking is converted, and the lost spaces are  not replaced

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

• Zoning compliance review : to ensure the ADU meets objective standards for size, setbacks, and height.
• Site plan and elevations: showing the entire property, existing structures, and the proposed ADU location.
• Architectural drawings: including floor plans and building elevations.
• Structural calculations and engineering: for new construction or significant modifications.
• Title 24 energy documentation: demonstrating compliance with California's energy code.
• Permit submission: through the City of San Carlos's permit application process, which may be online, in person, or by email.
  

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

Permit review times vary but are typically between 8 to 12 weeks depending on project complexity and city workload. Projects requiring corrections may take longer. Engaging professionals familiar with San Carlos's ADU process can help streamline approval.

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

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