Walnut

Walnut allows Accessory Dwelling Units (ADUs) and Junior ADUs (JADUs) on residential properties to increase housing opportunities. ADUs are permitted on lots with an existing or proposed single-family residence and recent state law updates have streamlined approvals by reducing restrictions on parking, size and permitting timelines. 

The city facilitates ADU development by minimizing barriers and providing guidance through its Planning Division.

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

• Detached ADU: A standalone residential unit separate from the primary dwelling
• Attached ADU: A unit that is attached to the primary residence
• Conversion ADU: Created by converting existing space such as a garage into a dwelling unit
• Junior ADU (JADU): A unit (up to 500 sq ft) created entirely within an existing single-family residence, with either shared or separate sanitation facilities

• Maximum Size:
  
  • Detached: Minimum allowance of 800 sq ft, with maximum typically ranging up to 1,000 sq ft depending on lot size, floor area ratio and zoning standards
  • Attached: Based on zoning standards, floor area ratio and lot coverage, but must allow at least 800 sq ft.
    
    
• Setbacks:
  
  • Minimum 4-foot side and rear setbacks; front setbacks follow underlying zoning requirements
    
    
• Height Limits:
  
  • Detached: Up to 16 feet by default; up to 18 feet if within ½ mile of transit
  • Attached: May reach up to 25 feet when attached to the primary residence
    
    
• Parking Requirements:
  
  • Parking requirements are reduced under state law; exemptions may apply depending on location and project conditions.

• One ADU is permitted per single-family residence and one JADU may also be allowed on the same lot.
• Separate exterior entrance is required for both ADUs and JADUs.
• ADU must include a full kitchen and independent sanitation facilities.
• JADU requires an efficiency kitchen and may share sanitation facilities.
• Plans must comply with zoning standards, building codes and city regulations.
• Applicants are encouraged to consult with the Planning Division before submitting permits

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

Recent state laws streamline the approval process and reduce permitting timelines for ADUs, allowing faster administrative review when requirements are met.

Engaging professionals familiar with Walnut ADU process can help streamline approval and potentially reduce delays.

ADUs are allowed on residentially zoned properties with an existing or proposed single-family residence. One ADU and one JADU are permitted per lot. Development standards such as floor area ratio, lot coverage and zoning regulations apply, but must still allow at least an 800 sq ft ADU.

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

ADU regulations are constantly evolving and may vary by city, county or even neighborhood.

Before starting your project, it’s always best to consult with a trained professional or certified ADU Specialist to ensure your plans align with current local requirements.