Zoning & Size Limits
| Requirement | Denver, CO | Boulder, CO |
|---|
| Allowed Zones | All residential zones | All single-family and multi-family zones |
| Max Size (Detached) | 864 sq ft | 800 sq ft (market-rate); 1,000 sq ft (affordable ADU program) |
| Max Size (Attached) | 864 sq ft | Up to 50% of principal structure or 1,000 sq ft max |
| Max Height | 24 ft maximum | 20-25 ft (detached, depends on roof pitch); 35 ft |
| Parking Required | 1 space per unit | No parking required (eliminated March 2025) |
| Owner Occupancy | Required in single-unit zones (owner must live in primary or | Not required (eliminated March 2025, per CO HB 24-1152) |
Setback Requirements
| Setback | Denver, CO | Boulder, CO |
|---|
| Rear Setback | Must be within rear 35% of lot; 5 ft minimum rear setback | 10 feet |
| Side Setback | 3 feet | 3 feet |
| Front Setback | 15 feet | 15 feet |
Permits & Timeline
| Detail | Denver, CO | Boulder, CO |
|---|
| Permit Timeline | 30-45 days | 40-60 days |
| Permit Fees | $1,600-$2,700 | $1,900-$3,200 |
| Impact Fees | Minimal | Minimal |
| Pre-Approved Plans | Extensive library 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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