These rules apply to UNINCORPORATED Maricopa County - communities like Sun City, Sun City West, Anthem, New River, and Sun Lakes - not Phoenix, Mesa, Scottsdale, or other incorporated cities, which have their own ADU codes. ADUs became legal by right countywide with text amendment TA250002, adopted December 10, 2025 to comply with Arizona's HB 2928 (A.R.S. 11-810.01) and carried into the modernized county zoning ordinance effective January 9, 2026. Every single-family lot may add at least one attached and one detached ADU; parcels of an acre or more can add a third if it's deed-restricted affordable. No public hearing, no extra parking, and no owner-occupancy requirement for long-term rentals.
Zoning & Size Requirements [1][2]
Yes — unincorporated Maricopa County allows ADUs. A detached ADU can typically be up to 1,000 sq ft under Arizona state law and the County's zoning code.
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| Where ADUs Are Allowed | By right on any lot where a single-family dwelling is allowed (Maricopa County Zoning Ordinance, per TA250002 and A.R.S. 11-810.01) |
| Max Size (Detached) | 1,000 sq ft or 75% of the primary dwelling's gross floor area, whichever is less - the ADU must always be smaller than the main house |
| Max Size (Attached) | Must stay within the building envelope of the principal dwelling and be smaller than it; the same 75%/1,000 sq ft state framework applies |
| Max Size (JADU) | No JADU category - Arizona law recognizes attached and detached ADUs only |
| Max Height | Standard district height (30 ft in rural and single-family districts); a detached ADU encroaching into a required side or rear yard is limited to 18 ft |
| Max Units | At least 1 attached + 1 detached ADU on any single-family lot; a second detached ADU (third unit) on parcels of 1+ acre if deed-restricted affordable to households at up to 80% of area median income. |
Setback & Parking Requirements [1][2]
Unincorporated Maricopa County requires a rear setback of about 5 ft for a detached ADU, and parking requirements vary by unit size or location. Owner-occupancy is not required — you can rent it out without living on the property.
| Rear Setback | District setbacks apply, but a detached ADU may come within 5 ft of the rear line (state law bars requiring more) and occupy up to 30% of a required yard |
| Side Setback | 5 ft minimum (same state-law floor); the ADU cannot sit over a utility easement without the utility's consent |
| Front Setback | Standard district front setback; the ADU must share a single street access point with the primary residence |
| Parking Required | None - the county may not require additional parking for an ADU or charge fees in lieu of it (A.R.S. 11-810.01(B)(3)) |
| Owner Occupancy | Not required for long-term ADU rentals - the county cannot require any family, marital, or employment relationship between the homeowner and the ADU tenant. Exception: short-term-rental properties whose ADU was finaled on or after Sept 14, 2024 require the owner to live on-site |
| Min Lot Size | None for the first two ADUs (1 attached + 1 detached); the third ADU requires a parcel of 1 acre or more |
Permit Process & Fees [3]
An ADU in unincorporated Maricopa County is approved ministerially (by-right) within a standard residential building-permit review cycle (no published ADU-specific target; permits are valid one year from issuance); permit fees are valuation- and square-footage-based per the county fee schedule - no ADU-specific fee, and no in-lieu parking fees are allowed.
| Approval Process | By right - no public hearing, variance, conditional use permit, or special exception. A standard residential building permit from Maricopa County Planning & Development is all that's required; building, fire, and septic codes apply, but the county may not demand commercial-code compliance or fire sprinklers |
| Review Timeline | a standard residential building-permit review cycle (no published ADU-specific target; permits are valid one year from issuance) |
| Permit Fees | valuation- and square-footage-based per the county fee schedule - no ADU-specific fee, and no in-lieu parking fees are allowed |
| Impact Fees | No ADU-specific impact fees published; if sewer is unavailable the county may require an adequately sized septic system before construction |
| Plan Check | Standard residential plan review through Planning & Development (Permit Center, 602-506-3301) |
| Pre-Approved Plans | No county pre-approved ADU plan program as of mid-2026 |
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Construction Costs [4]
Building an ADU in unincorporated Maricopa County typically costs $120,000-$240,000 (Phoenix-metro market estimate) ($135-$270 (market estimate) per sq ft); a garage conversion runs $60,000-$140,000 (market estimate).
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Construction costs in unincorporated Maricopa County mirror the surrounding Inland Empire market. Rural parcels can cost more due to septic, well, access, and fire-hazard (WUI) requirements, so treat these as planning ranges and get local bids.
| Average Build Cost | $120,000-$240,000 (Phoenix-metro market estimate) |
| Cost per Sq Ft | $135-$270 (market estimate) |
| Garage Conversion | $60,000-$140,000 (market estimate) |
| Prefab ADU (Installed) | $100,000-$220,000 (market estimate) |
Finance Your ADU Project
Most ADU projects are funded through HELOCs, construction loans, or cash-out refinancing. Compare rates from top lenders.
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Rental Income Potential [5]
| Avg Rent (1 Bedroom) | $1,200-$1,650/mo (Phoenix-metro market) |
| Avg Rent (2 Bedroom) | $1,500-$2,100/mo |
| Short-Term Rental | Yes with limits - Arizona preempts STR bans, and the county's first STR standards (TA250002) allow one whole-unit STR per parcel at a time, no by-room rentals, no events; if the ADU's certificate of occupancy is dated Sept 14, 2024 or later, the owner must live on the property to STR it |
| Est. Annual ROI | 7-10% annual return (market estimate) |
Recent Law Changes
What's Changed Recently
- May 2025: Arizona HB 2928 signed - new A.R.S. 11-810.01 required every county to allow ADUs by January 1, 2026 or accept ADUs on all residential lots without limits
- October 23, 2025: county Planning & Zoning Commission recommended TA250002 (ADU + short-term-rental amendment) 9-0
- December 10, 2025: Board of Supervisors adopted TA250002 and the comprehensively modernized zoning ordinance (TA25001, 5-0) - the county's first explicit ADU framework, replacing the old guest-house rules
- January 9, 2026: the modernized Maricopa County Zoning Ordinance took effect, carrying the ADU and STR provisions
Tips for Building an ADU in Unincorporated Maricopa County
- Sun City, Sun City West, Anthem, New River, and Sun Lakes are unincorporated - these County rules apply, not Phoenix or Scottsdale codes (note: age-restricted communities' private HOA covenants still apply on top)
- The 75%-of-home cap binds before 1,000 sq ft on homes under ~1,333 sq ft - measure your primary dwelling first
- Keep a detached ADU out of required yards to use the full 30 ft district height; inside a required yard it drops to 18 ft
- Planning to Airbnb it? If your ADU is finaled after Sept 14, 2024, you must live on the property - long-term rental has no such condition
- On 1+ acre parcels, a third unit is available if you accept an 80%-AMI affordability deed restriction
ADU Builders in Maricopa County
Looking for an ADU builder in Maricopa County? ADU projects need a contractor experienced with local zoning, the permit process, and utility connections — not every general contractor has built one. We match Maricopa County homeowners with experienced local ADU contractors who provide free, no-obligation quotes. Getting at least three bids typically saves 20-40% on the same scope.
Cities Within Maricopa County
If your property is inside one of these incorporated cities, follow that city's ADU code — not the County rules above:
Sources & References
All data on this page is sourced from official government records and verified market data. View our full methodology.
- A.R.S. 11-810.01 - Accessory dwelling units (counties) Government Data — Accessed 2026-07-30
- TA250002 - Report to the Board of Supervisors (ADUs / Short-Term Rentals) Planning Department — Accessed 2026-07-30
- Maricopa County Zoning Ordinance Update (TA25001, effective Jan 9, 2026) Planning Department — Accessed 2026-07-30
- Angi - ADU Construction Cost Data Market Data — Accessed 2026-07-30
- HUD Fair Market Rents Government Data — Accessed 2026-07-30
- HB 2928 (2025) bill text - Arizona Legislature Government Data — Accessed 2026-07-30
- KJZZ - Maricopa County approves zoning for multiple accessory dwelling units (Dec 10, 2025) News Source — Accessed 2026-07-30
Frequently Asked Questions
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