ADU Permits: Mesa vs Phoenix
How do adu permits rules compare between Mesa, AZ and Phoenix, AZ?
Mesa has fewer restrictions than Phoenix.
Mesa, AZ
Maricopa County
Mesa permits ADUs by right in all single-residence districts under Mesa Zoning Ordinance Title 11, Section 11-31-3, as updated by Ordinances 5883 and 5950 to comply with Arizona HB 2720. Internal, attached, and detached ADUs are allowed. Maximum 75% of the primary residence interior habitable area or 1,000 sq ft, whichever is less. No minimum lot size and no additional parking required.
View full Mesa rules →Phoenix, AZ
Maricopa County
Phoenix processes ADU permits through Planning and Development under PZC Section 608 (Casita Ordinance) and 2024 Phoenix ADU updates. Arizona HB 2928 (effective 2025) preempts local restrictions in cities over 75,000 residents, requiring ministerial approval for ADUs meeting state standards.
View full Phoenix rules →Key Facts Comparison
| Fact | Mesa | Phoenix |
|---|---|---|
| State Law | AZ HB 2720 (effective 2025) | AZ HB 2928 (2025) |
| City Code | MZO §11-31-3 (Ord. 5883) | Phoenix PZC Section 608 |
| Max Size | 75% primary or 1,000 sq ft | 75% primary or 1,000 sq ft |
| Min Lot Size | None | - |
| Parking | Not required | - |
| ADUs Per Lot | 1 attached + 1 detached by right | - |
| Review Type | - | Ministerial (no hearing) |
| Review Time | - | 10-20 business days |
Highlighted rows indicate differences between cities.
Mesa FAQ
Do I need a permit for a Mesa ADU?
Yes. All ADUs require building permits through Mesa Development Services. Under HB 2720 and MZO Section 11-31-3, review is ministerial (over-the-counter) without public hearings. Full structural, electrical, mechanical, and plumbing trade permits are required.
How many ADUs can I build on my Mesa lot?
At least one attached and one detached ADU are permitted by right on any lot where a single-family dwelling is permitted, with no minimum lot size. On lots of at least one acre, a third ADU (second detached) is permitted only if deed-restricted as affordable to households at 80% AMI.
Phoenix FAQ
Do I need a permit for a Phoenix ADU?
Yes. All ADUs require building permits through Phoenix Planning and Development under PZC Section 608. Under HB 2928, review is ministerial (over-the-counter) without public hearings, but full structural and trade permits are required.
How big can my Phoenix ADU be?
Under Arizona HB 2928, ADUs are limited to 75 percent of the primary dwelling size or 1,000 square feet, whichever is less. Phoenix cannot impose a smaller maximum size than state law.
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