Zoning & Size Limits
| Requirement | Denver, CO | Boulder, CO |
|---|
| Allowed Zones | All zones that allow a single-family dwelling (citywide as o | All single-family and multi-family zones |
| Max Size (Detached) | Up to 1,000 sq ft on lots over 7,000 sq ft (864 sq ft on 6,000-7,000 sq ft lots; ~650 sq ft on smaller lots) — varies by zone district | 800 sq ft (market-rate); up to 1,000 sq ft (affordable ADU program) |
| Max Size (Attached) | Up to 1,000 sq ft (varies by zone district) | Up to 50% of principal structure or 1,000 sq ft max |
| Max Height | 24 ft / 1.5 stories maximum | 20-25 ft (detached, depends on roof pitch); confir |
| Parking Required | Not required (no parking minimum for ADUs per HB24-1152 / CB | Not required (no parking minimum for ADUs per Ordinance 8650 |
| Owner Occupancy | Not required (removed by CB24-1303, effective Dec 16, 2024; | Not required (removed by Ordinance 8650, eff. March 8, 2025; |
Setback Requirements
| Setback | Denver, CO | Boulder, CO |
|---|
| Rear Setback | Must be within rear 35% of lot; 5 ft minimum rear setback | Confirm with Boulder Planning (reduced rear setbacks ~3 ft apply to market-rate detached ADUs near alleys) |
| Side Setback | Varies by lot width (typically 3-5 ft); confirm with Denver CPD | 3 feet |
| Front Setback | Matches the primary structure front setback (varie | 15 feet |
Permits & Timeline
| Detail | Denver, CO | Boulder, CO |
|---|
| Permit Timeline | 4-7 months realistic from application to issued permit (zoning + building review) | 40-60 days |
| Permit Fees | $500-$5,000 building permit + ~$2,055 Denver Water SDC (rising to $2,170 on Jul 1, 2026); total permit/utility typically $6K-$10K | $1,900-$3,200 |
| Impact Fees | Denver Water system development charge applies; see fees | Minimal |
| Pre-Approved Plans | Pre-approved/standard plan options available | Available |
Construction Costs
| Cost | Denver, CO | Boulder, CO |
|---|
| Avg Build Cost | $140,000-$280,000 | $160,000-$320,000 |
| Cost Per Sq Ft | $130-$260 | $140-$280 |
| Garage Conversion | $70,000-$160,000 | $80,000-$180,000 |
| Prefab ADU | $100,000-$230,000 | $120,000-$270,000 |
Rental Income Potential
| Rental | Denver, CO | Boulder, CO |
|---|
| 1BR Avg Rent | $1,400-$1,900/mo | $1,600-$2,100/mo |
| 2BR Avg Rent | $1,800-$2,500/mo | $2,000-$2,800/mo |
| Short-Term Rentals | Yes, with STR license | Limited restrictions |
| Est. ROI | 7-9% annual return | 6-8% annual return |
Which City Is Better for ADUs?
Denver scores 8/10 while Boulder scores 8/10 on our ADU-friendliness index.
Both cities offer viable ADU development opportunities — the best choice depends on your specific property, budget, and goals.
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