The City of Palo Alto permits ADUs across most residential zones. Palo Alto 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.

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

• Detached ADU: New freestanding structure separate from the main home, like a backyard cottage. 
• Attached ADU:  New structure (may include some converted space) sharing at least one wall with the primary home.
• Conversion ADU: Convert non-livable space (such as attached garage, storage, or carport) to an ADU. 
• Junior ADU (JADU): Up to 500 sq ft, carved out of existing space within the home with an efficiency kitchen

• Maximum Size:
  
  • Detached: Up to 800 sq ft
  • Attached: 900 SF (1 bedroom) or 1,000 SF for 2+ bedrooms
• Setbacks:
  
  • Minimum 4 ft from side and rear property lines
• Height Limits:
  
  •  Palo Alto’s residential zone height limits for primary structures are often 18 ft (with roof pitch allowances) in R-1 zones.
• Parking Requirements:
  
  • Additional parking is not required if the ADU is:
    
    • Located within ½ mile of public transit (bus stop, train station, etc.)
    • Part of an existing structure conversion (e.g., garage, basement, or internal space)
    • In a designated historic district or if on-street parking permits are required but not available to ADU residents

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

• Zoning compliance review (setbacks, height, lot coverage, floor area limits)
• Site plan and elevations showing the ADU location and design
• Structural calculations and engineering for new construction or additions
• Title 24 energy documentation for compliance with California energy codes
• Permit submission through the City of Palo Alto’s online portal
• Fire department review for access, egress, and safety compliance
• Architectural drawings of the proposed ADU
• Utility connection approvals, if a new detached ADU requires separate services
  

Homeowners should also review Palo Alto’s current fee schedule, utility connection requirements, fire code compliance, and any owner-occupancy rules for Junior ADUs.

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

Most residential zones in Palo Alto are eligible for ADUs, including R-1, R-2, and R-M zones. There are generally no minimum lot sizes for ADUs, though lot coverage and floor area ratio limits apply. Some lots in hillside areas, historic districts, or with special setback requirements may have additional restrictions.

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