Mesa, AZ Accessory Structures: ADU Rules (2026)

Section 11-31-3 of the Mesa Zoning Ordinance sets the citywide framework for accessory dwelling units. Any lot with an existing Single Residence qualifies for one attached and one detached ADU regardless of zoning district, and a lot of one acre or more can add a second detached ADU if at least one unit is rented as a restricted-affordable dwelling to households earning up to 80% of area median income. There's no minimum lot size requirement to establish an ADU. The unit must have a separate, independent entrance from the primary residence with no internal connecting doorway, and it may contain only one kitchen, whether partial or full.

Manufactured homes, RVs, and trailers cannot be used as an ADU. New attached or detached ADU structures must observe a minimum 5-foot side and rear setback, while front and street-side setbacks follow the primary residence's underlying zoning district requirements. Height for an attached or detached ADU must match the primary residence's height limit for that district, and the unit must comply with the same lot coverage and building coverage caps that apply to the underlying zoning district. ADUs in a Historic District must additionally comply with Chapter 74 of the Zoning Ordinance, and every ADU must meet all applicable residential building code requirements.

Utilities must be shared with the primary residence's water, sewer, and electric provider, and an ADU cannot be built over a current or planned Public Utility Easement without written consent from the utility. No additional off-street parking spaces are required to add an ADU to a property.