Side by side · Arizona
Compare ADU rules across Arizona
Flexible on where you build? The same backyard cottage can be routine in one city and impossible next door. This table puts 7 Arizona cities side by side so you can shortlist the friendly ones before reading a single ordinance, or narrow it to just the cities you are deciding between. Every value is summarized from the city's own code; open a city's page for the full notes, citations, and fine print.
The short answers
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| City | Detached ADU | Attached / internal | Max size | Owner occupancy | Extra parking | Approval |
|---|---|---|---|---|---|---|
| Chandler | Allowed | Allowed | 75% of the gross floor area of the existing single-family dwelling or 1,000 sq ft, whichever is less; gross floor area means the interior habitable area of the single-family dwelling | Not required | None; no ADU parking requirement in the current code. The former requirement of one additional off-street space (old Sec. 35-2202(9)(c)) was struck by Ord. 5113, and current Sec. 35-2202 expressly excludes ADUs from accessory-building standards | Permitted use |
| Gilbert | Allowed | Allowed | 75% of the primary dwelling's gross square footage (no flat cap); ADUs over 1,000 sq ft additionally need an Administrative Use Permit and must sit within the building envelope | Not required | None for ADUs | Permitted use |
| Mesa | Allowed | Allowed | 75% of the primary residence's interior habitable area or 1,000 sq ft, whichever is less (applies to attached and detached) | Not required | None. No additional parking spaces are required for an ADU, and a garage or carport converted to an ADU does not have to be replaced elsewhere on the lot | Permitted use |
| Phoenix | Allowed | Allowed | 75% of the primary dwelling's gross floor area, and no more than 1,000 sq ft on lots up to 10,000 sq ft net; on lots over 10,000 sq ft net, the lesser of 3,000 sq ft or 10% of net lot area | Not required | No additional parking for an ADU; the Section 702 parking table requires 2 spaces per primary dwelling unit only | Permitted use |
| Scottsdale | Allowed | Allowed | 1,000 sq ft or 75% of the main dwelling's gross floor area, whichever is less (first ADU); 500 sq ft max for any additional ADU on the same lot | Not required | No additional parking required for the ADU | Permitted use |
| Tempe | Allowed | Allowed | 1,000 sq ft of interior habitable area or 75% of the main residence's gross floor area, whichever is less; on lots of 1 acre or more, 2,000 sq ft or 75% of the main residence, whichever is less | Not required | None; no additional vehicle parking is required for an ADU | Permitted use |
| Tucson | Allowed | Allowed | 75% of the principal dwelling's gross floor area, not to exceed 1,000 sq ft; an ADU up to 650 sq ft is allowed regardless of the principal dwelling's size | Not required | None: 'Vehicular parking is not required to be provided for accessory dwelling units.' | Permitted use |
Summarized from each city's ordinance text, most recently read July 2026. Tap a value marked with an info icon to see exactly what it depends on, straight from the ordinance. Nearly every value has zone, lot-size, or process caveats beyond that; the per-city pages carry the full notes and code citations. Treat this as orientation, not a permit determination.
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Reading the table
- Detached ADU is the make-or-break column for backyard cottages: minimum lot sizes (often 8,000 to 14,500 sq ft) hide behind many of the "Allowed" values, so check your lot before celebrating.
- Attached / internal (basement apartments, additions) is legal almost everywhere and is usually the path of least resistance.
- Approval: "Permitted use" means staff-level sign-off; "Conditional use" means a public hearing, which adds time, cost, and uncertainty.
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