Accessory Dwelling Unit Size and Development Standards in the City of Mesa
In the City of Mesa, an Accessory Dwelling Unit (ADU) is limited to a maximum interior habitable area of 1,000 square feet or 75% of the primary residence’s interior habitable area, whichever is less. According to the City of Mesa Zoning Ordinance, these units are permitted in various zoning districts, including Agricultural (AG), Residential (RS, RSL, RM), and Downtown (DR) areas, provided they meet specific configuration and setback requirements.
Maximum Unit Size and General Requirements
The City of Mesa Zoning Ordinance establishes specific size limitations for any Accessory Dwelling Unit to ensure it remains subordinate to the primary structure. The interior habitable area must not exceed the thresholds established in the following table:
| Standard | City of Mesa Requirement |
|---|---|
| Maximum Habitable Area | 1,000 sq. ft. or 75% of Primary Residence (whichever is less) |
| Minimum Lot Size | No minimum lot size required to establish an ADU |
| Maximum Kitchens | One (1) per ADU |
| Height Limit | Must comply with primary residence height limits for the district |
| Prohibited Structures | Manufactured homes, RVs, and trailers cannot be used as ADUs |
[Section 11-31-3(B) and (C)]
District Applicability and Density
Under the City of Mesa Zoning Ordinance, property owners are generally allowed one attached ADU and one detached ADU per lot in districts where single-family residences are permitted. These districts include:
- Agricultural District (AG) [Section 11-4-2]
- Residential Districts (RS, RSL, and RM) [Section 11-5-2]
- Downtown Districts (DR) [Section 11-8-3]
If a parcel in the City of Mesa is one acre or larger, a second detached ADU may be permitted if at least one of the units is deed-restricted as affordable housing for households earning up to 80% of the area median income [Section 11-31-3(A)].
Setback and Placement Standards
The City of Mesa requires specific distances between ADUs and property lines. While existing conforming detached accessory buildings (like garages) can sometimes be converted without new setbacks, new construction must adhere to the following standards:
| Requirement for New ADUs | Minimum Distance |
|---|---|
| Side Yard Setback | 5 feet |
| Rear Yard Setback | 5 feet |
| Front Yard Setback | Same as underlying zoning district for primary residence |
| Secondary Front Setback | Same as underlying zoning district for primary residence |
| Separation from Primary Building | Not explicitly specified, but must have a separate entrance |
[Section 11-31-3(D)]
Additional Development Standards
The City of Mesa Zoning Ordinance requires that an ADU maintain a separate and independent entrance from the primary residence [Section 11-31-3(B)]. Furthermore, if a garage or carport is converted into an ADU, the City of Mesa does not require the property owner to replace the covered parking for the primary residence elsewhere on the lot [Section 11-31-3(G)]. All ADUs must be served by the same water, sewer, and electric utility providers and meters as the primary residence [Section 11-31-3(H)].
Sections Cited
- Section 11-4-2: Land Use Regulations (Agricultural)
- Section 11-5-2: Land Use Regulations (Residential)
- Section 11-8-3: Land Use Regulations (Downtown)
- Section 11-31-3: Accessory Dwelling Unit
- Section 11-86-2: Residential Use Classifications (Definitions)