Accessory Dwelling Unit (ADU) Regulations in Mesa, Arizona
In the City of Mesa, one attached and one detached Accessory Dwelling Unit (ADU) are permitted on any lot or parcel that contains an existing single-family residence, regardless of the underlying zoning district. However, in non-residential districts such as Commercial, Employment, or Public/Semi-Public zones, ADUs are only permitted if they are accessory to an existing, legal non-conforming residential use. Additionally, ADUs are strictly prohibited on properties located within Airport Overflight Area 1 (AOA 1) or Airport Overflight Area 2 (AOA 2).
Permitted Zoning Districts
The City of Mesa identifies specific permissions for ADUs across various base and overlay districts. While Section 11-31-3 provides a broad allowance for any lot with an existing single residence, the individual district tables specify the following:
Residential and Agricultural Districts
ADUs are permitted by right in the following districts, provided the property is not in an airport overflight restricted area [Table 11-4-2, Table 11-5-2]:
- Agricultural (AG)
- Single Residence (RS-6, 7, 9, 15, 35, 43, 90)
- Residential Small Lot (RSL-2.5, 3, 4, 4.5)
- Multiple Residence (RM-2, 3, 4, 5)
Downtown and Transect Districts
ADUs are integrated into the urban form of the Downtown and Form-Based Code areas [Table 11-8-3, Table 11-58-3.A]:
- Downtown Residence (DR-1, DR-2, DR-3)
- Downtown Business and Core (DB-1, DB-2, DC): Permitted only if an existing non-conforming residential use is located on the lot.
- Transect Zones (T3N, T4N, T4NF, T4MS, T5N, T5MSF, T5MS, T6MS): Permitted as a "Secondary Dwelling Unit."
Commercial, Employment, and Public Districts
In these districts, the City of Mesa allows ADUs only as an accessory to an existing non-conforming residential use [Table 11-6-2, Table 11-7-2, Table 11-10-2]:
- Commercial (NC, LC, GC, OC, MX)
- Employment (PEP, LI, GI, HI)
- Public and Semi-Public (PS)
Special Residential Classifications
ADUs are specifically permitted in the following specialized residential developments [Section 11-34-2]:
- Recreational Vehicle Subdivisions
- Manufactured Home Subdivisions
Development Standards for ADUs
All Accessory Dwelling Units in the City of Mesa must adhere to specific size, height, and setback requirements to ensure compatibility with the primary residence and neighboring properties.
| Standard | Requirement |
|---|---|
| Quantity Allowed | One (1) attached and one (1) detached ADU per lot. |
| Maximum Unit Size | 75% of the primary residence's interior habitable area, or 1,000 sq. ft., whichever is less. |
| Minimum Setbacks | 5 feet for side and rear yards (new structures). |
| Front Setbacks | Must comply with the primary residence setbacks for the underlying district. |
| Maximum Height | 15 feet if located within 5 feet of property lines; otherwise, the limit of the underlying district applies. |
| Parking | No additional parking spaces are required for an ADU. |
General Requirements and Restrictions
- Existing Residence Required: The Primary Building must be under construction or fully constructed prior to initiating the construction of an ADU [Section 11-30-17].
- Entrance: An ADU must have a separate and independent entrance from the primary residence [Section 11-31-3].
- Kitchen Facilities: An ADU may contain a partial or full kitchen, but no more than one kitchen is allowed per ADU [Section 11-31-3].
- Prohibited Structures: Manufactured homes, recreational vehicles (RVs), and trailers may not be used as an ADU [Section 11-31-3].
- Affordable Housing Bonus: One additional detached ADU (total of three units on one lot) may be permitted if the lot is one acre or larger and at least one of the ADUs is deed-restricted as affordable housing for households earning up to 80% of the area median income [Section 11-31-3].
- Airport Restrictions: ADUs are not permitted on any property subject to the AOA 1 or AOA 2 overflight areas [Section 11-19-2].
Sections Cited
- Section 11-4-2: Agricultural District Land Use Regulations
- Section 11-5-2: Residential Districts Land Use Regulations
- Section 11-6-2: Commercial Districts Land Use Regulations
- Section 11-7-2: Employment Districts Land Use Regulations
- Section 11-8-3: Downtown Districts Land Use Regulations
- Section 11-10-2: Public and Semi-Public District Land Use Regulations
- Section 11-19-2: Runway Protection Zones and Airport Overflight Areas
- Section 11-30-17: Detached Accessory Buildings or Structures
- Section 11-31-3: Accessory Dwelling Unit
- Section 11-34-2: Permitted Uses (Manufactured Home/RV)
- Section 11-58-3.A: Composite Use Table (Transect Zones)