Fort Collins ADU Permits & Requirements
City fees $6.9K–$25K · 3–6 month timeline · Up to 750–1,000 sf
Quick Answer
Fort Collins ADUs: $170K–$380K
Permits: $6.9K–$25K · Updated April 2026
Permit & City Fee Breakdown
| Fee Type | Cost |
|---|---|
| Basic Development Review (BDR) | $6,925 |
| Building Permit | $1,000–$3,000 |
| Plant Investment Fee (water/sewer) | $5,000–$27,175 |
| Utility capacity, transportation & stormwater | Varies |
Figures are estimates and change annually. Verify the current schedule with the City of Fort Collins and Fort Collins Utilities before budgeting.
Permit Process Timeline
Eligibility & Conceptual Design Review
1–3 weeksConfirm your zone allows an ADU under HB24-1152; use the City's free Conceptual Design Review for staff feedback
Plan Preparation
3–6 weeksSite, utility, tree, and stormwater plans plus radon-resistant and snow/wind-rated structural design
Basic Development Review (BDR)
2–3 monthsAdministrative zoning and site review of exterior design and placement — no public hearing
Building Permit Review
6–8 weeksInterior layout, structural, mechanical, and building-code compliance
Construction & CO
4–7 monthsInspections, radon-system install and test, and Certificate of Occupancy
Track Every Dollar of Your ADU Build
TerraLine is the construction finance cockpit that shows your loan balance, budget burn, and forecast at completion — all on one screen. No more spreadsheets.
Zoning & Requirements
Max ADU Size
750–1,000 sf
Height Limit
≤ primary / zone max
Setbacks
5 ft side / 8 ft rear
Parking
None required
Key Regulations
- HB24-1152 (effective June 30, 2025) + Fort Collins' Feb 14, 2025 Land Use Code update allow ADUs in every zone that permits a single-family home
- Detached ADU up to 750 sf (main home under 1,667 sf) or 1,000 sf / 45% of main home; converted structures up to ~800 sf
- No added off-street parking required; owner-occupancy is not required for ADU rentals
- Short-term rental generally not allowed on new ADUs — verify STR licensing with the City
- Radon-resistant construction advised (Larimer County is EPA Radon Zone 1); roofs need a 30 psf snow load
- Colorado's broader land-use preemption package faces home-rule litigation; HB24-1152 is in effect — verify current status
Climate & Construction Notes
Larimer County is EPA Radon Zone 1, with Fort Collins homes averaging around 10 pCi/L — plan for radon-resistant construction and licensed testing. Roofs must be engineered for a 30 psf snow load, and foothills lots on the west side face higher design wind speeds under the Colorado Front Range gust map. The semi-arid, freeze-thaw climate rewards good drainage, frost-protected foundations, and expansive-soil detailing.
Frequently Asked Questions
How long does it take to get an ADU permit in Fort Collins?
Plan on 2–3 months for the Basic Development Review plus 6–8 weeks for the building permit — roughly 3–6 months of permitting, even though the process is administrative with no public hearing. Total project time from design to CO is usually 9–13 months.
What types of ADUs are allowed in Fort Collins?
Detached, attached, basement, and converted-structure (e.g., garage) ADUs are all allowed. Detached units are capped at 750 sf on smaller lots or up to 1,000 sf (45% of the main home) on larger ones.
Do I need to live on the property to build an ADU in Fort Collins?
No — Fort Collins does not require owner-occupancy for ADU rentals. Rules can change, so confirm the current standards with the City of Fort Collins planning department.
More Fort Collins ADU Resources
Ready to Start Your ADU Project?
Join hundreds of homeowners who used our guides to navigate their ADU build successfully.
✓ Free comprehensive guide ✓ Vetted contractor list ✓ No credit card needed