The City of Mountain View permits ADUs across most residential zones. Mountain View 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.

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

• Detached ADU: Separate dwelling unit built on the same lot as the primary residence
• Attached ADU: built into the existing single-family home
• Conversion ADU: Converts existing, underutilized space within a single-family home into a legal, independent living unit
• Junior ADU (JADU): Up to 500 sq ft, converted from part of the home,  existing single-family home, requires owner occupancy, and must have an efficiency kitchen

• Maximum Size:
  
  • Detached: Up to 1,200 square feet
  • Attached: Up to 1,000 square feet or 50% of the primary residence's size, whichever is less
• Setbacks:
  
  • Minimum 4 ft setbacks from the rear and side property lines
• Height Limits:
  
  • Typically 28 ft maximum
• Parking Requirements:
  
  • Additional parking is not required if the ADU is:
    
    • Within one-half mile of a public transit stop
    • An internal conversion of the existing main building
    • Within a historic district

To building permit (including electrical, mechanical, plumbing) and a demolition permit are required. No planning permit is required:

• Zoning Compliance Review: A complete set of electronic building plans
• Site Plan and Elevations: A completed Mountain View Green Building Residential Worksheet
• Architectural Drawings: Structural calculations
• Structural Calculations and Engineering: Energy calculations
• Title 24 Energy Documentation: Electrical load calculations
• Permit Submission: School Impact Fees
  

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

Permit times are usually 4 to 6 months depending on the complexity of the project and workload in the city. Some simple projects can be expedited, whereas those with corrections or requiring additional information may take longer. Having experts familiar with Mountain View's ADU process can help make approval easier.

Accessory dwelling units shall be a permitted use in any district where residential uses are permitted. Junior accessory dwelling units shall be permitted in the single-family zoning districts within an existing single-family residence, or as part of a proposed single-family residence.

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