Fort Collins ADU Zoning Rules & Permit Guide

ADU Regulations in Fort Collins, Colorado

Updated September 29, 2026

At the base of the Rocky Mountains in Larimer County, Fort Collins has one of Colorado's most developed ADU programs. The city allows ADUs on lots as small as 3,500 square feet with specific design standards reflecting the community's character.

Below is a summary of the key zoning rules applicable to Accessory Dwelling Units in Fort Collins as of 2026. Regulations are governed by local zoning ordinances, as Colorado has no statewide ADU mandate (HB 24-1152 addresses transit density).

Additional Local Requirements for Fort Collins

• ADU on lots 3,500 sq ft minimum
• Minimum ADU size: 300 sq ft
• One ADU per single-family lot
• Short-term rental of ADU prohibited
• Fort Collins has its own established ADU program

Frequently Asked Questions About ADUs in Fort Collins

Can I build an ADU in Fort Collins?

Fort Collins permits ADUs in lower-density neighborhoods. Owner occupancy is required and the ADU cannot be used as a vacation rental.

What is the maximum ADU size allowed in Fort Collins?

ADUs in Fort Collins can be up to 1,200 square feet, subject to the property's zoning and lot coverage limits. Always confirm the exact allowed size with the Fort Collins planning department before designing your project.

What are the setback requirements for an ADU in Fort Collins?

ADUs in Fort Collins generally require setbacks of 5 ft rear, 5 ft side. Colorado has no statewide ADU mandate, so the exact setback figures come from Fort Collins's own zoning code — confirm them with the city planning department before you design.