Zoning & Size Limits
| Requirement | Phoenix, AZ | Gilbert, AZ |
|---|
| Allowed Zones | Single-family residential zones | All single-family zoning districts (Gilbert Development Serv |
| Max Size (Detached) | 1,000 sq ft on lots up to 10,000 sq ft (75% of primary dwelling, whichever is less); on lots over 10,000 sq ft, the lesser of 3,000 sq ft or 10% of net lot area | 75% of the primary residence's gross square footage (state law guarantees at least the lesser of 1,000 sq ft or 75%) |
| Max Size (Attached) | 75% of primary dwelling, capped at 1,000 sq ft (lots ≤10,000 sq ft) | 75% of the primary residence's gross square footage (state law guarantees at least the lesser of 1,000 sq ft or 75%) |
| Max Height | 15 ft when within required rear/side yards (greate | Same as the underlying zoning district standard fo |
| Parking Required | No additional parking required (ARS 9-461.18 / AZ HB 2720 pr | No additional parking may be required (ARS 9-461.18) |
| Owner Occupancy | Not required for long-term rental; owner must reside on-site | Not required for long-term rentals; no familial or pre-exist |
Setback Requirements
| Setback | Phoenix, AZ | Gilbert, AZ |
|---|
| Rear Setback | 5 feet (3 ft for some detached configurations per ZO 706; statute caps rear/side at 5 ft) | 5 feet maximum required (ARS 9-461.18 caps rear setbacks at 5 ft) |
| Side Setback | 5 feet (3 ft for some detached configurations per ZO 706) | 5 feet maximum required (ARS 9-461.18 caps side setbacks at 5 ft) |
| Front Setback | Per underlying zoning district (no ADU-specific fr | Per underlying zoning district — Confirm with Gilb |
Permits & Timeline
| Detail | Phoenix, AZ | Gilbert, AZ |
|---|
| Permit Timeline | 60-90 days | Confirm with Gilbert Development Services (480-503-6700) |
| Permit Fees | $2,500-$4,200 | Building permit and plan review fees based on valuation — Confirm with Gilbert Development Services |
| Impact Fees | $900-$1,600 | System development fees apply to new dwelling units — Confir |
| Pre-Approved Plans | Limited availability | No pre-approved plan library — Confirm with Gilber |
Construction Costs
| Cost | Phoenix, AZ | Gilbert, AZ |
|---|
| Avg Build Cost | $120,000-$240,000 | $130,000-$260,000 |
| Cost Per Sq Ft | $135-$270 | $150-$280 |
| Garage Conversion | $60,000-$140,000 | $60,000-$140,000 |
| Prefab ADU | $85,000-$200,000 | $90,000-$210,000 |
Rental Income Potential
| Rental | Phoenix, AZ | Gilbert, AZ |
|---|
| 1BR Avg Rent | $1,250-$1,700/mo | $1,500-$1,750/mo |
| 2BR Avg Rent | $1,600-$2,200/mo | $1,850-$2,300/mo |
| Short-Term Rentals | Varies by neighborhood | Arizona law allows STRs with registration; ADU-specific STR |
| Est. ROI | 7-10% annual return | 6-9% annual return |
Which City Is Better for ADUs?
Phoenix scores 6/10 while Gilbert scores 6/10 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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