Real ADU pricing across Phoenix, Tucson, and Arizona's other major markets, shaped by extreme summer heat loads, xeriscape water requirements, and a labor market that swings hard by region.
HB 2720, signed by Gov. Katie Hobbs on May 21, 2024, requires every Arizona city with more than 75,000 residents (16 cities, covering roughly two-thirds of the state's population) to allow at least one attached and one detached ADU per single-family lot by right. It also dropped owner-occupancy and off-street parking requirements statewide, and capped size at 75% of the primary home's floor area or 1,000 sq ft, whichever is less, with setbacks no greater than 5 feet. Cities had until January 1, 2025 to adopt compliant local rules — after that date, ADUs became permitted by default in any city that hadn't. HB 2928 (2025) followed up with technical clarifications.
Phoenix got there first. The Phoenix City Council legalized backyard casitas on its own in September 2023, a year before the state mandate — then updated its ordinance again in late 2024 to fall in line with HB 2720. Phoenix's rules now allow up to two ADUs plus a possible third on lots over an acre, and specifically bar ADUs from operating as short-term rentals. A related 2024 measure, SB 1415, drew controversy in the legislature over provisions addressing ADU kitchens and short-term rental restrictions — a reminder that Arizona's ADU framework is still actively being amended, not settled once and for all in 2024.
Cities above the statutory population threshold must allow ADUs by right; local permits, HOA covenants, and development rules still apply.
These are planning benchmarks, not a permit quote, eligibility ruling, or legal opinion. Confirm zoning, building, utility, site, private-covenant, fee, and timing requirements with the current local authorities. See the 51-jurisdiction law directory and national permit guide.
Freestanding backyard structure. Scottsdale and Flagstaff push toward the top of this range; Tucson and Mesa toward the bottom. HB 2720 caps size at 1,000 sqft or 75% of the primary home, whichever is less.
Detached ADU Guide →An addition sharing a wall with the main house. Shared utility connections reduce hookup costs versus a fully detached unit, and still qualifies under HB 2720's by-right guarantee.
Attached ADU Guide →Arizona's dry climate keeps most garages in solid structural condition, making full conversion one of the most cost-efficient paths to an ADU statewide.
Garage Conversion Guide →True basements are rare in Arizona — slab-on-grade construction dominates due to soil and cost conditions statewide. Homeowners with an existing lower level should still confirm feasibility with a local contractor.
Basement ADU Guide →Several prefab ADU providers serve the Phoenix metro market. Units must be engineered for Arizona's extreme summer heat load, but typically reach occupancy faster than site-built construction.
Prefab ADU Overview →A converted interior space within the existing footprint of the main house, with its own private entrance. The lowest-cost path to an ADU in Arizona, since no new foundation or structure is required.
Junior ADU Overview →
*Total-cost ranges outside Phoenix are derived from regional $/sq ft data at a representative ~600 sq ft build; verify against local bids before publishing final figures. Note that Flagstaff — driven by Northern Arizona University housing demand and constrained mountain-town supply — runs higher than Phoenix on a per-sq-ft basis, which is a genuine market condition, not an error.
Effective framework: HB 2720 (2024) + HB 2928 (2025). Cities above the statutory population threshold and counties operate under state ADU standards; local permits and development rules still apply. Permit fees and review timing remain planning estimates until confirmed for the specific property.
Calculate My ROI →HB 2720 and HB 2928 already guarantee your right to build. These moves target the design fees, climate costs, and timeline factors that remain within your control.
Calculate My ADU ROI →
Illustrative 1-bedroom layout. Actual floor plans vary by ADU type, size, local code, and homeowner needs.
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