Zoning & Size Limits
| Requirement | Denver, CO | Phoenix, AZ |
|---|
| Allowed Zones | All residential zones | Single-family residential zones |
| Max Size (Detached) | 864 sq ft | 900 sq ft |
| Max Size (Attached) | 864 sq ft | 75% of primary dwelling, capped at 1,000 sq ft (lots ≤10,000 sq ft) |
| Max Height | 24 ft maximum | 15 ft (use permit may allow more) |
| Parking Required | 1 space per unit | No additional parking required (AZ HB 2720, effective Jan 20 |
| Owner Occupancy | Required in single-unit zones (owner must live in primary or | Not required |
Setback Requirements
| Setback | Denver, CO | Phoenix, AZ |
|---|
| Rear Setback | Must be within rear 35% of lot; 5 ft minimum rear setback | 15 feet |
| Side Setback | 3 feet | 5 feet |
| Front Setback | 15 feet | 25 feet |
Permits & Timeline
| Detail | Denver, CO | Phoenix, AZ |
|---|
| Permit Timeline | 30-45 days | 60-90 days |
| Permit Fees | $1,600-$2,700 | $2,500-$4,200 |
| Impact Fees | Minimal | $900-$1,600 |
| Pre-Approved Plans | Extensive library available | Limited availability |
Construction Costs
| Cost | Denver, CO | Phoenix, AZ |
|---|
| Avg Build Cost | $140,000-$280,000 | $120,000-$240,000 |
| Cost Per Sq Ft | $130-$260 | $135-$270 |
| Garage Conversion | $70,000-$160,000 | $60,000-$140,000 |
| Prefab ADU | $100,000-$230,000 | $85,000-$200,000 |
Rental Income Potential
| Rental | Denver, CO | Phoenix, AZ |
|---|
| 1BR Avg Rent | $1,400-$1,900/mo | $1,250-$1,700/mo |
| 2BR Avg Rent | $1,800-$2,500/mo | $1,600-$2,200/mo |
| Short-Term Rentals | Yes, with STR license | Varies by neighborhood |
| Est. ROI | 7-9% annual return | 7-10% annual return |
Which City Is Better for ADUs?
Denver scores 8/10 while Phoenix scores 6/10 on our ADU-friendliness index.
Denver edges ahead overall. Both cities offer viable ADU development opportunities — the best choice depends on your specific property, budget, and goals.
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