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

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

• Detached ADU: The unit is separated from the primary
• Attached ADU: The unit is attached to the primary structure
• Conversion ADU: A guest bedroom is converted into an independent living unit. 
• Junior ADU (JADU): The unit is no more than 500 sq. ft., contained entirely within a single-family residence.

• Maximum Size:
  
  • Detached: Up to 850 sq. ft. or 1,000 sq
  • Attached: Up to 50% of the primary dwelling’s floor area, not exceeding 1,000 sq. ft.
• Setbacks:
  
  • Minimum 4 ft from yard, rear and side property lines
• Height Limits:
  
  • Typically, 16 ft, A ground floor plate height that exceeds 12 feet or a roof height that exceeds 18 feet
• Parking Requirements:
  
  • Additional parking is not required if the ADU is:
    
    • No additional parking is required for single and multiple family.

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

• Review of zoning compliance to ensure the ADU is compliant with Belmont's ADU and zoning regulations
• Site plans and elevations that indicate the location, size, and design of the ADU
• Floor plans and architectural drawings
• Structural and engineering calculations (foundation, framing, seismic, etc.)
• Title 24 / energy code compliance reports
• Building permit application and ministerial review
  

Homeowners need to also examine Belmont's fee structure, utility connection allowances (e.g. sewer, water), tree removal regulations, fire safety code adherence, and any construction inspections that are needed.

Permitting review times are but usually between 6 and 12 weeks, varying according to the complexity of the project, completeness of application, and workload in the city. ADU applications with ministerial requirements are usually processed within 60 days under state statute. Those that need plan corrections, further reviews, or inter-department coordination take longer. Working with professionals who understand Belmont's ADU permitting process can make approval easier.

Most of Belmont's residential areas are qualified for ADUs, such as R-1, HIA-1, VHDR, and RM zones. ADUs in most areas do not have minimum lot sizes. Some environmentally sensitive or hillside zones will have unique limitations as to setbacks, height, or lot coverage.

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