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

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

• Detached ADU:  Stand-alone units separate from the primary dwelling.
• Attached ADU: Units physically connected to the primary dwelling.
• Conversion ADU: conversion of a garage, the addition of new habitable space
• Junior ADU (JADU): cannot be larger than 500 square feet in total floor area

• Maximum Size:
  
  • Detached: Up to 850 sq ft (1 bedroom) or 1,000 sq ft (2+ bedrooms) 
  • Attached: Up to 50% of the primary dwelling’s floor area, not exceeding 1,000 sq ft. 
• Setbacks:
  
  • Minimum 4 ft from side and rear property lines
  • Minimum 5 ft separation from other structures on the lot
• Height Limits:
  
  • A new detached ADU may not exceed 18 feet in height.
  • A new attached ADU shall not exceed the height limit as established by the Zoning District
• Parking Requirements:
  
  • Additional parking is not required if the ADU is:
    
    • No additional on-site parking is required. (JADUs must replace parking on-site when garage space is converted)

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

• File a completed application to the Building Division.
• Accompany your application with the ADU and Junior ADU (JADU) Zoning Checklist and Design Standards Checklist.
• Submit clear plans illustrating the location, dimensions, and elevations of the proposed ADU.
• Verify sufficient water, sewer, and electrical services are available. Utility services to ADUs are required to be undergrounded.
• Provide sprinklers in the ADU/JADU when necessary for the main house.
  

Homeowners must also examine Union City's existing fee structure, utility connection fees, and fire code standards.

The review time for Accessory Dwelling Units (ADUs) permits in Union City depends on project complexity and work load for the city. No specific time frames are described in the sources given, but the city provides resources to guide homeowners through the permitting process.

The majority of residential areas in Union City are eligible for ADUs, both single-family and multi-family residential areas. There are no minimum lot requirements for ADUs in most residential areas. Special limits on setbacks, height, or lot coverage could apply in some hillside or environmentally sensitive areas.

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