Hermosa Beach

One ADU is permitted on each residential lot. The accessory dwelling unit shall be either attached to the existing primary dwelling, located within the living area of the existing dwelling, attached to an existing accessory structure, or detached from the existing primary dwelling and located on the same lot as the existing primary dwelling.

One JADU is permitted on each residential lot. The JADU shall not be considered a separate or a new dwelling unit for the purposes of applying building or fire codes.

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

• Detached ADU: A separate standalone unit on the same lot as the main home
• Attached ADU: Connected to the primary residence
• Conversion ADU: Created from existing space such as garages or interior rooms
• Junior ADU (JADU): A small unit within the existing home, typically up to 500 sq. ft under state standards

• Maximum Size:
  
  • Detached: Up to 1,200 sq ft maximum in most cases, must still comply with zoning, setback and building code requirements.
  • Attached: Up to 1,200 sq. ft maximum in most cases (or limited by applicable zoning standards).
    
    
• Setbacks:
  
  • Standard requirement: 4 feet from side and rear property lines
  • Conversions within existing structures may be exempt from setbacks
    
    
• Height Limits:
  
  • Detached ADUs generally limited to about 16 feet, depending on structure type
  • Some cases may allow up to 20-25 feet, especially above garages or under updated code provisions
    
    
• Parking Requirements:
  
  • Parking is often not required if the ADU is:
    
    • Within ½ mile of public transit 
    • Part of a conversion (garage/interior)

To build an ADU in Hermosa Beach, applicants typically must submit:

• Building permit application 
• Site plan showing property layout and setbacks 
• Architectural drawings (floor plans + elevations) 
• Structural, grading, or soils reports (if required for hillside or site conditions) 
• Energy compliance documentation (Title 24, including solar requirements for new construction ADUs in some cases) 
• Utility and fire code compliance review

Homeowners should also review Hermosa Beach current fee schedule, utility connection requirements and fire code compliance.

ADU applications in Santa Monica (as this coastal-review context suggests) are required to be reviewed within 60 days once a complete application is submitted, in accordance with California’s ministerial approval timeline. However, delays are common when additional reviews are needed. 

These delays typically arise from missing documents, required coastal or geotechnical reviews, or plan check corrections. As a result, the practical timeline from submission to permit approval is usually around 2-4 months, depending on the complexity of the project and how quickly revisions are addressed.

In Santa Monica, ADUs are permitted in most residential zones, including single-family neighbourhoods and there is no minimum lot size requirement under California state law. However, all ADU projects must still comply with local zoning standards and development regulations.

Key requirements include adherence to Municipal Code Chapter 17.21, as well as applicable building and fire safety codes. In properties located within the coastal zone, additional coastal regulations may also apply, which can introduce further review and design considerations.

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

You should also review Municipal Code Chapter 17.21, which contains the city’s specific ADU regulations, along with statewide standards from the California Department of Housing and Community Development, which set the baseline rules that local ordinances must follow.