The City of Fairfax permits ADUs across most residential zones. Fairfax 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.

Fairfax aligns with California’s broader ADU legislation but has its own requirements for height, setbacks, and design reviewThe City of Fairfax permits ADUs across most residential zones. Fairfax 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.

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

• Detached ADU: A unit located separately from the main house
• Attached ADU: A new unit sharing at least one wall with the main dwelling.
• Conversion ADU: A unit created by converting existing space within the main home or another permitted accessory structure.
• Junior ADU (JADU): A smaller unit (up to 500 sq. ft) created within the existing main dwelling.

• Maximum Size:
  
  • Detached: Up to 1,200 square feet 
  • Attached: Up to 50% of the habitable floor area of the existing or proposed primary dwelling
    
• Setbacks:
  
  • Maximum 4 ft side yard and rear yard and 10 ft front yard.
• Height Limits:
  
  • Detached: Maximum height is 16 ft 
  • Attached: Maximum height isUp to 25 ft
• Parking Requirements:
  
  • Additional parking is not required if the ADU is:
    
    • Located within one-half mile walking distance of public transit
    • Located within an architecturally or historically significant historic district
    • Part of the proposed or existing primary residence, or an accessory structure 
    • Where on-street parking permits are required but not offered to the ADU occupant

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

• Zoning compliance review with the Planning Department
• Site plan and elevations showing setbacks, height, and lot coverage
• Architectural drawings consistent with town design standards
• Structural calculations and engineering reports (if applicable)
• Title 24 energy compliance documentation
• Building permit submission through the Town of Los Altos Hills’ eTrakit online portal
  

Homeowners should also review Fairfax’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 Jose’s ADU process can help streamline approval.

Most residential zones are eligible for ADUs, including R-1 and R-2 districts.There are no minimum lot size requirements for ADUs in most areas of Fairfax.

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