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

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

• Detached ADU: Separate from the primary dwelling with a separate exterior entrance and full independent living facilities.
• Attached ADU: Connected to the primary dwelling with a separate exterior entrance and full independent living facilities
• Conversion ADU: conversion of an existing accessory structure or a portion of the existing primary residence to an ADU
• Junior ADU (JADU): A JADU is no more than 500 square feet in size and contained entirely within the walls of an existing or proposed single-family residence

• Maximum Size:
  
  • Detached: 1 bedroom 850 sq ft 2+ bedrooms 1,000 sq ft
  • Attached: 1 bedroom 850 sq ft 2+ bedrooms 1,000 sq ft
• Setbacks:
  
  • Minimum 4 feet from side and rear property lines
• Height Limits:
  
  • Detached: Typically up to 16 feet
  • Attached: Up to 25 feet 
• Parking Requirements:
  
  • Additional parking is not required if the ADU is:
    
    • If the ADU is located within one-half mile of public transit, such as a bus stop or train station. 
    • If the ADU is part of an existing structure, such as a garage conversion.
    • If the ADU is a new construction and not located within one-half mile of public transit.

To build an ADU in Hercules, the following approvals and submittals are typically required:

• Zoning Compliance Review: Ensure the proposed ADU complies with local zoning regulations
• Site Plan and Elevations: Provide detailed drawings showing the ADU's location and design
• Architectural Drawings: Submit detailed plans of the ADU's structure and layout
• Structural Calculations and Engineering: Include calculations and engineering details to ensure the ADU's structural integrity
• Title 24 Energy Documentation: Demonstrate compliance with California's energy efficiency standards
• Permit Submission: Submit the permit application through the City of Hercules’s online portal
  

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

Most residential zones are eligible for ADUs, including R-1, R-2, and R-M zones. There are no minimum lot size requirements for ADUs in most areas of Hercules. Some hillside or environmentally sensitive zones may have special restrictions.

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