Maricopa County's Zoning Ordinance: ADU and Short-Term Rental Rules (2025 Update)

This page is general information for property owners in unincorporated Maricopa County, not legal advice.

What this ordinance does

If your parcel is in unincorporated Maricopa County, no city issues your permit. The county does, under the Maricopa County Zoning Ordinance (MCZO). In December 2025 the Board of Supervisors replaced the ordinance's whole layout with a comprehensive update. That update brought the county's casita and short-term rental rules in line with Arizona's 2025 county ADU statute. The ADU rules now live in Article 602.3 and the short-term rental rules in Article 602.2.

Status

• In force. The Board of Supervisors approved text amendment TA250001, the comprehensive MCZO update, by a 5–0 vote on December 10, 2025 (Maricopa County Planning & Development, Zoning Ordinance page).
• Effective January 9, 2026 (same page: "The effective date of the updated MCZO is January 9, 2026").
• The ordinance itself dates to 1969: "This Ordinance was first adopted and became effective on May 29, 1969" (MCZO Section 102). The cover of the current text reads "Reformatted 2001 and 2025 · Latest Revision 2025."
• The companion case that never became law. A narrower emergency amendment, TA250002 (ADUs and short-term rentals only), ran alongside TA250001. The county's own board report says: "If TA250001 (MCZO Update) is adopted then TA250002 becomes unnecessary and will be administratively withdrawn." TA250001 was adopted. If you have read that "TA250002" is the county's ADU law, that is wrong.
• State mandate behind it: A.R.S. § 11-810.01, added by Laws 2025, ch. 217 (HB 2928), which required counties to adopt complying ADU regulations by January 1, 2026.
• Last verified: September 1, 2026.

What it actually says

ADUs are a permitted use. "In accordance with Arizona State Statute, ADUs are a permitted use on any lot or parcel zoned for single-family residential use. A public hearing, variance, or special permit shall not be required" (Article 602.3.1).

How many. "At least one attached and one detached ADU shall be permitted on each lot or parcel where a single-family dwelling is allowed" (602.3.2.A). On a lot of one acre or more, "at least one additional detached ADU shall be permitted provided that at least one ADU on the lot be a deed restricted-affordable dwelling unit to be rented to households earning up to eighty percent of the area median income" (602.3.2.B).

Size. "No ADU shall exceed the size of the principal dwelling" (602.3.3.A). "On lot or parcel less than one acre, the size of the ADU shall be a maximum of 75% of the primary dwelling unit or 1,000 square feet whichever is less" (602.3.3.B).

Who may live there. ADUs "may be leased or occupied independently of the principal dwelling as long-term rental housing," and "No familial, marital, or employment relationship is required between occupants of the principal dwelling and the ADU" (602.3.4).

Design standards. ADUs follow "the same height, lot coverage, and frontage standards as single-family dwellings within the zoning district," with three exceptions (602.3.5):

• A detached ADU may sit in the required rear or side yard but "shall not occupy more than 30% of any required yard and shall not be nearer than five feet to any side or rear lot line" (602.3.5.A).
• A detached ADU that encroaches into a required side or rear yard "shall be limited to a height of 18 feet" (602.3.5.B).
• "All ADUs shall share a single access point to the street with the primary residence; internal driveways may diverge from this point" (602.3.5.C).

Older ADUs. An ADU lawfully built before this article that does not meet current standards "may be continued as a legal nonconforming use. Alterations or expansions must comply with this Article" (602.3.6).

Short-term rental of an ADU. "No more than one ADU may be used as a short-term rental" (602.3.7). The general STR rules in Article 602.2 add: an STR is a rental of "no more than 30 consecutive days"; "The owner of a short-term rental must reside on the property if the property contains an accessory dwelling unit unless a certificate of occupancy, certificate of completion or similar final approval for the accessory dwelling unit was issued by the County on or before September 13, 2024"; whole-unit rental only, no by-the-room rentals; "Only one (1) STR unit may be rented per parcel at any given time"; and no commercial events, signage, or retail operation (602.2.1–.5).

Definition. "ACCESSORY DWELLING UNIT: A habitable space with independent sleeping, bathing and cooking quarters either detached from or attached to and designed without interior entry into the primary dwelling" (MCZO Chapter 2).

Where it applies

• Covered: the "entire unincorporated area" of Maricopa County (MCZO Section 103). If your parcel is inside a city or town, that city's ordinance applies instead, even if your mailing address says otherwise.
• Not covered: parcels inside any incorporated city or town; tribal land.
• State-law exclusions: A.R.S. § 11-810.01(H) removes tribal land, land near military airports or in high-noise or accident-potential zones, and land near FAA-licensed, general-aviation, or public airports with a noise level above 65 decibels from the county ADU mandate. Whether and how Article 602.3 applies those exclusions on the ground was not established from the ordinance text we read.

What's still unsettled

• Section numbers moved. Before the 2025 update, readers cited "MCZO §503" for accessory structures. In the current text, Section 503 is "Purpose of Commercial Zoning Districts." Any guide that still cites §503 for ADUs is reading the superseded layout.
• Size on larger lots. The 75%-or-1,000-square-foot cap in 602.3.3.B is written for lots under one acre. For lots of one acre or more, the text we read sets only the "no larger than the principal dwelling" ceiling. Confirm with the county before designing a larger unit.
• Septic. A.R.S. § 11-810.01(I) lets a county require an adequately sized septic system before an ADU is built where sewer is unavailable. We did not locate the county's implementing text.
• The September 13, 2024 date in Article 602.2.2 is the day before the state ADU law took effect on September 14, 2024. The ordinance does not explain the choice; we report it as written.
• Airport exclusions. See "Where it applies."
• Fees and permit process. Not covered here.

Related pages

• Arizona's ADU Law: HB 2720
• HB 2928 — the 2025 ADU follow-up law

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• Current Maricopa County Zoning Ordinance (PDF, header dated December 10, 2025): https://esd.maricopa.gov/DocumentCenter/View/4785
• Maricopa County Planning & Development, Zoning Ordinance page (TA250001 vote, effective date): https://www.maricopa.gov/6159/Zoning-Ordinance
• Board of Supervisors report, TA250002, hearing December 10, 2025 (withdrawal condition): https://www.maricopa.gov/AgendaCenter/ViewFile/Item/10027?fileID=97120
• A.R.S. § 11-810.01 (county ADU statute): https://www.azleg.gov/ars/11/00810-01.htm
• Laws 2025, ch. 217 (HB 2928): https://www.azleg.gov/legtext/57leg/1R/laws/0217.htm

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