Coconino County, AZ Accessory Structures: ADU Rules (2026)

4 of the Zoning Ordinance governs Accessory Dwellings on Residential-zoned and Planned Community single-family lots, aiming to 'increase housing supply' and 'achieve housing affordability goals' while preserving neighborhood character. Every lot may add one attached and one detached Accessory Dwelling; lots over one acre can add a second detached unit only if it is deed-restricted to personal residential use or rental as Affordable Housing. Size is tiered by percentage, not a flat cap: any single-family lot can build up to 600 square feet of livable area regardless of lot or house size, and larger lots can go further, capped at 75 percent of the main dwelling's livable area, with hard ceilings of 1,000 square feet detached and 1,200 square feet attached.

Only Single Family Dwellings, and Modular and Manufactured Homes, may serve as an Accessory Dwelling, and the ordinance expressly bars Travel Trailers, Recreational Vehicles, and Mobile Homes from that role. A detached unit must sit no closer than 200 feet from the principal dwelling on lots under 4 acres, or 500 feet on lots 4 acres and larger, and must still meet the underlying zone's front and street-side setbacks plus a flat 5-foot side and rear setback. Building, Environmental Quality, and Engineering permits are required, reviewed through Planning and Zoning.

The Community Development Director can waive the separation-distance or square-footage limits through an Administrative Adjustment, but only to the minimum extent needed, for reasons such as converting an existing structure, protecting an environmentally sensitive feature, enabling solar or water-conservation design, or working around site infrastructure constraints; a decision on that request can be appealed to the Board of Adjustment as a Variance.