Accessory Dwelling Unit (ADU) Regulations in Fort Collins

Max Size- 

• Detached: 
  
  • 750 sq/ft if the primary structure is less than or equal to 1,667 sq/ft                  
  • 1,000 sq/ft or 45% of primary structure (whichever is less) if the primary structure is greater than 1,667 sq/ft
• Attached: 
  
  • The greater of 750 sq/ft or 45% of the primary dwelling unit (if on floor level at or above grade)
  • The greater of 750 sq/ft or 100% of the floor level (if on floor level or below grade)

Max Height- Cannot exceed height of primary structure

As of June 30, 2025, new state laws require ADUs to be allowed in all zones where a single-family home is permitted. This means homeowners in Fort Collins will have broader opportunities to build ADUs. However, local zoning and design requirements must still be met.

Fort Collins has specific size and design limitations for ADUs to ensure they fit within existing neighborhoods:

• Maximum ADU Size:
  
  • 800 sq/ft for detached ADUs or 50% of the main home’s living area, whichever is smaller.
  • For ADUs built within a basement or attic, up to 100% of the floor level can be used.
• Height Limits:
  
  • Detached ADUs cannot exceed the height of the primary home or 30 feet, whichever is lower.
• Setbacks & Placement:
  
  • Detached ADUs must comply with minimum rear and side yard setbacks.
• Architectural Compatibility:
  
  • ADUs must maintain a cohesive look with the primary residence, including roof pitch, siding, and materials.

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• HB 24-1152 requires cities to allow ADUs without designated parking, except in these cases:
  ✔ If no parking is currently required for the primary home, parking cannot be required for the ADU.
  ✔ If the lot does not have an existing parking space for the primary home, no additional parking is required.

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• ADUs must share utility connections with the primary home separate water or sewer taps are not allowed.
• Homeowners are responsible for all utility charges associated with the ADU.
• If the ADU requires expanded utility capacity, the homeowner may need to pay for larger service lines or additional system fees.

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• HB 24-1152 prohibits cities from requiring owner occupancy meaning ADUs can be rented out separately from the primary home.
• ADUs cannot be sold separately from the main home—they must remain part of the same lot.
• Short-term rentals (STRs) are still prohibited, except in Planned Unit Developments (PUDs) where STRs were previously allowed.

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Under HB 24-1152, all ADU approvals must be handled administratively—meaning there are:
✔ No public hearings
✔ No subjective design reviews
✔ dNo neighborhood approval require

Building an ADU in Fort Collins requires multiple approvals and permits, including:

1. Building Permit Application – Submitted with architectural drawings and site plans.
2. Plan Review & Approvals – Fort Collins’ Planning and Development Department will review the ADU design for compliance.
3. Construction & Inspections – Once permitted, construction must comply with city building codes and pass inspections before occupancy is allowed.

The permit application fee varies based on the size and complexity of the ADU.

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Navigating Fort Collins’ ADU regulations can be complex, but Kindred Tiny Homes makes the process easy by handling every step from zoning approvals to final construction.

• We specialize in Fort Collins’ ADU regulations ensuring compliance with all zoning and permitting requirements.
• We provide full-service ADU development—from design and engineering to construction and project management.
• We maximize your investment creating a high-quality ADU that enhances property value and meets your needs.

If you’re considering building an ADU in Fort Collins, contact us today for a free consultation, we’ll guide you through your options and help bring your vision to life!

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