Fort Collins vs. Greeley ADU rules
Fort Collins and Greeley take opposite approaches to where an ADU can go. Since Ordinance 009-2025 took effect in February 2025, Fort Collins allows ADUs in every zone where a house is allowed, with no added parking requirement for the ADU itself and only a staff-level Basic Development Review — though that review's flat fee alone is $6,925, and the city puts total fees at $20,000–25,000. Greeley's code (GMC §24-403.b) permits ADUs only in R-M, R-H, C-L, C-H, MU-L, and MU-H districts — not the single-family R-E, R-L, or H-A zones — and still requires one parking space per bedroom, an apparent state-law conflict, though Greeley wasn't on the state's October 2025 non-compliance list.
✓ Verified against code · August 19, 2026
Fort Collins rules run under Land Use Code §3.1.8 and zone-district standards, adopted by Ordinance 009-2025, in effect since February 14, 2025.
✓ Verified against code · August 19, 2026
Greeley rules run under Greeley Municipal Code Title 24 (Development Code), §24-403, adopted by Ord 35-2021 (ADU section last amended by Ord 7-2023), in effect since February 21, 2023.
Rule by rule
| Rule | Fort Collins | Greeley |
|---|---|---|
| ADUs allowed per lot | One ADU per lot — attached or detached — accessory to a detached house, duplex, triplex, or mobile home, in every zone district since February 2025.LUC §3.1.8; Art. 2 zone tables | One ADU per lot, with a detached house or duplex/multi-unit building — detached or within the principal building (attic/basement). As codified, permitted only in the R-M, R-H, C-L, C-H, MU-L, and MU-H districts — not in R-E, R-L, or H-A, where single-family homes are permitted, an apparent conflict with the state statute.GMC §24-403.b; Table 24-4-2; contrast C.R.S. 29-35-403(1) |
| Maximum size | New detached: 750 sq ft if the home is under 1,667 sq ft, otherwise the lesser of 1,000 sq ft or 45% of the home. Converting an existing legal accessory structure: 800 sq ft. Attached: the greater of 750 sq ft or 45% (basement ADUs: up to the full floor).LUC §3.1.8 floor-area tables | The lesser of 60% of the home's living area or 1,200 sq ft; a detached ADU is additionally capped as a secondary building at 50% of the home's footprint (up to 1,200 sq ft). On small homes the 60% formula can block ADUs in the 500–750 sq ft range the statute protects.GMC §24-403.b.3; Table 24-5-2; contrast C.R.S. 29-35-402(18) |
| Detached ADU height | 1.5 stories / 28 ft, or the zone standard — Old Town caps at 24 ft or the house's height, whichever is less.LUC §3.1.8; §2.1.6 | 25 ft, but no taller than the principal structure — and larger secondary buildings also face a 9-ft wall / 22-ft roof-peak limit.Table 24-5-2; §24-502.c.2 |
| Detached ADU setbacks | At least 5 ft from the house and 10 ft behind its front wall; side and rear per zone (RL example: side 5 ft, rear 15 ft — dropping to 5 ft along an alley).LUC §3.1.8; §2.1.4 | Side and rear 5 ft; street side 20 ft; at least 12 ft behind the house's front building line and 6 ft from the house. No alley exception.Table 24-5-2; §24-502.c.1 |
| Off-street parking | None for the ADU — only the home's own minimums apply, and a tandem space can count.LUC Div. 5.9; city ADU page | As codified: one space per bedroom for a 'secondary dwelling' (the term is undefined; applying it to ADUs is the plain reading), confined to the garage, driveway, or street directly in front — well beyond what the statute permits a city to require.Table 24-7-3; §24-403.b.4; contrast C.R.S. 29-35-403(2)(a), (3) |
| Owner-occupancy | None — no owner-occupancy language anywhere in the code.LUC (verified absence); C.R.S. 29-35-403(2)(b) | None — the ADU section contains no owner-occupancy condition.GMC §24-403.b |
| Lot coverage / floor area | ADU floor area is excluded from Old Town's rear-lot floor-area caps and from the RL district's minimum-lot-area ratio — deliberate carve-outs that keep ADUs from eating the lot budget.LUC §2.1.6; §2.1.4 | Greeley uses minimum lot open space per building type rather than a maximum coverage; the detached ADU also lives under the 50%-of-footprint secondary-building cap.Table 24-5-1; §24-503 |
| Permit path & timeline | Basic Development Review — a staff decision — in every zone, then a building permit; a free conceptual design review is offered first. The BDR flat fee is $6,925, and the city itself pegs typical total fees at $20,000–25,000. No published day-count for review.LUC Div. 4.2; city ADU page | Permitted accessory use — staff review and/or site plan approval, then a building permit via eTRAKiT. Published plan-review times: 20 working days for new construction, 10 for additions and remodels.§24-402.a.1(a); city building-permits page |
Fort Collins: worth knowing
- The fee reality is the headline: $6,925 flat for review plus impact and utility fees lands most projects at $20,000–25,000 in fees before a shovel turns.
- ADUs permitted on or after January 1, 2024 may not be short-term rentals (earlier licenses grandfathered).
- No new dwelling units in the Poudre River 100-year floodplain.
- The lot under a home and ADU can't be split, but a condo plat is allowed.
- The ADU needs its own electric meter.
Fort Collins: on our watchlist
Land Use Code Phase 2 (commercial corridors and centers) continues through 2026 but hasn't touched ADU standards to date.
Greeley: worth knowing
- The 'clearly subordinate' standard: the ADU must be visibly secondary and compatible with the main building in design, entrance, and parking placement.
- No ADU-specific short-term-rental ban — unusual on the Front Range.
- Since January 30, 2026, no permits issue in a subdivision until the subdivision or phase is complete.
- The apparent statute conflicts (zones, parking, size formula) have drawn no adopted or visibly pending corrective ordinance — and also no state enforcement listing. A homeowner in R-E, R-L, or H-A is in genuinely uncertain territory: the statute says yes, the code says no.
Greeley: on our watchlist
No HB24-1152 corrective amendment found through August 2026 — and, a genuine puzzle, no state non-compliance listing either. We watch both the council record and the state's quarterly compliance reviews.
Full detail: Fort Collins · Greeley · back to the Colorado hub. Not legal advice — every fact above cites the code section it comes from; check the cite, or ask your city’s planning department to confirm your specific lot.