The County of Santa Clara permits ADUs across most residential zones. County of Santa Clara 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.

County of Santa Clara aligns with California’s broader ADU legislation but has its own requirements for height, setbacks, and design review.

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• Detached ADU: detached from the primary residence
• Attached ADU: ADU that is physically attached to the primary dwelling.
• Conversion ADU: Created by converting an existing structure such as a garage, storage building, or other internal space 
• Junior ADU (JADU): Up to 500 sq ft, must be fully within an existing single-family home or ADU; must have its own entrance and kitchenette but can share a bathroom.

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• Maximum Size:
  
  • Detached: Up to 1,200 sq ft
  • Attached: Up 50% of the primary dwelling size except to allow for a minimum size of 800 square feet.
• Setbacks:
  
  • Minimum 4 feet from side and rear boundaries.
• Height Limits:
  
  • Same as primary dwelling if ADU complies with residential setbacks, or 16 feet otherwise.
• Parking Requirements:
  
  • Additional parking is not required if the ADU is:
    
    • Typically requires 1 parking space, but exemptions apply (e.g., near transit, conversion ADUs, within historic district exceptions, etc.)
    • JADUs require no parking

To build an ADU in County of Santa Clara, the following approvals are typically required:

• Zoning compliance review / Ministerial planning approval & building permits required.
• Submission of site plan and elevations showing existing and proposed structures.
• Architectural drawings (floor plans, elevations, etc.).
• Structural calculations and engineering (for new construction or conversion).
• Title 24 energy documentation (meeting energy-efficiency / state code standards).
• Permit submission through the county’s permit/online portal (building permit once plans approved).
  

Homeowners should also review County of Santa Clara ’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 county workload. Projects requiring corrections may take longer. Engaging professionals familiar with County of Santa Clara ’s ADU process can help streamline approval.

Most residential zones are eligible for ADUs, including R-1, R-2, and R-M zones. There are no minimum lot sizes for ADUs in most areas of the County of Santa Clara. Some hillside or environmentally sensitive zones may have special restrictions.

For the most current and complete information, refer directly to the County of Santa Clara.