Do I Need a Building Permit in Arizona?
Arizona building permit rules. Counties must require a permit above $1,000, cities decide for themselves, and state law stops a prior owner's unpermitted work from blocking yours.
On unincorporated county land, yes if the work costs more than $1,000 — A.R.S. 11-321(A) makes that permit mandatory. Inside a city or town it depends on that municipality's own ordinance, because the state statute is written to govern municipalities that require permits without itself requiring them.
The county rule carries a dollar figure; the city rule carries none
A.R.S. 11-321(A) puts a duty on the county, not a choice: "Except in those cities and towns that have an ordinance relating to the issuance of building permits, the board of supervisors shall require a building permit for any construction of a building or an addition to a building exceeding a cost of $1,000 within its jurisdiction." Read the exception carefully, because it is wider than it first looks — it lifts the county duty in cities and towns with an ordinance "relating to the issuance of building permits", not only in those that require one. The municipal side never supplies the missing requirement. A.R.S. 9-467(A) opens "Any municipality requiring the issuance of a building permit shall transmit one copy of the permit to the county assessor and one copy to the director of the department of revenue", and every operative subsection after it is addressed to a municipality that already requires permits. So inside city limits the question is about the local ordinance, and state law does not answer it for you; on unincorporated land above $1,000 it is already answered.
You do not inherit the previous owner's unpermitted work
Arizona says this twice in identical words — at 9-467(F) for municipalities and 11-321(H) for counties: "If a person has constructed a building or an addition to a building without obtaining a building permit, a municipality shall not require a subsequent owner to obtain a permit for the construction or addition done by the prior owner before issuing a permit for a building addition except that this section does not prohibit enforcing an applicable ordinance or code provision that affects the public health or safety." Two limits are inside that sentence rather than outside it. It protects a subsequent owner, so it does nothing for the person who did the unpermitted work. And the closing clause preserves enforcement of anything bearing on public health or safety, so genuinely unsafe work can still be pursued against you. What it removes is the specific blocking move that strands buyers: a permit desk refusing your new addition until you first retroactively permit somebody else's old one.
Three more things the permit desk may not ask for
First, a tax or business licence as the price of the permit. Both 9-467(E) and 11-321(E) bar requiring "an applicant for a building permit to hold a transaction privilege tax license or business license as a condition for issuing the building permit" — but the municipal version carries a second sentence the county version does not, allowing a city or town to require a permit holder who has no business licence "to apply for a business license within thirty days after issuing the building permit". In a city that is a sequencing rule, not an exemption. Second, a particular utility. 9-467(B) and 11-321(B) declare a utility provider's authority to serve customers "a matter of statewide concern", subsection C forbids denying a permit application "based on the utility provider proposed to provide utility service to the project", and subsection D forbids setting fees or requirements that have the effect of restricting that choice; "utility service" is defined as water, wastewater, natural gas including propane, or electric service to an end user. Third, your physical presence — but only in a county, and only conditionally. 11-321(F) reads "Where deemed of public convenience, the board of supervisors shall allow the application for and the issuance of building permits by mail." That opening clause is the whole of the hedge: the county decides whether public convenience is served. Title 9 gives cities and towns no counterpart.
The ADU mandate is real, and it stops at the city line and at 75,000 people
A.R.S. 9-461.18(A) requires a municipality to "adopt regulations that allow on any lot or parcel where a single-family dwelling is allowed" at least one attached and one detached accessory dwelling unit as a permitted use, at up to seventy-five percent of the single-family dwelling's gross floor area or one thousand square feet, whichever is less. "Permitted use" is defined at (I)(5) as approval "without requiring a public hearing, variance, conditional use permit, special permit or special exception", which is what gives the mandate its force. Subsection B then forbids requiring additional parking, requiring the unit to match the house's exterior design, roof pitch or finishing materials, setting rear or side setbacks more than five feet from the property line, or requiring a familial, marital or employment relationship between the occupants. The limits matter as much as the mandate. Subsection H confines the whole section to "a municipality with a population of more than seventy-five thousand persons". Subsection G excludes lots on tribal land, in the vicinity of a military airport or ancillary military facility, and in airport territory with a noise level above sixty-five decibels. And it sits in Title 9, so counties are not covered at all and unincorporated land takes nothing from it. Where it does apply it has teeth: under (F), a municipality that failed to adopt the required regulations on or before January 1, 2025 must allow accessory dwelling units "on all lots or parcels zoned for residential use in the municipality without limits". Building, fire and public health and safety codes still apply under (D), with two carve-outs — a municipality may not require an accessory dwelling unit to comply with a commercial building code or to contain a fire sprinkler.
What we did and did not find about a statewide building code
A.R.S. 34-461 is the section most often reached for on this question, and it is narrower than its reputation. It sits in Title 34, "Public Buildings and Improvements", and subsection J fixes its subject: "'public building' means a building or appurtenance to a building that is built in whole or in part with public monies." Its genuinely useful rule for that class is subsection B — a public building in an area that has not adopted local codes "shall be designed or constructed according to the state fire code adopted by the office of the state fire marshal and the building, plumbing, electrical and mechanical codes that apply in the largest city in the county in which the building is located". That is a borrowing rule for public projects, and the only statewide code it names is the fire code. None of it reaches a house or a privately funded commercial building. We read Titles 9 (Cities and Towns), 11 (Counties), 34 (Public Buildings and Improvements), 36 (Public Health and Safety) and 41 (State Government) — five of the forty-seven titles currently in force, Titles 2 and 24 having been repealed — and found no statute adopting a building code for private construction across Arizona. That is a description of where we looked rather than a guarantee about the other forty-two, and the practical consequence is the same either way: the document that decides your project is your city or county ordinance. (Arizona Revised Statutes as published by the Arizona State Legislature at azleg.gov and read on 9 September 2026. That site states the compilation has been updated to include the revised sections from the 57th Legislature, 1st Regular Session, and that the next update will not take place until after the conclusion of the 57th Legislature, 2nd Regular Session, which convened in January 2026 — so any change made in the 2026 session may not yet appear in the text quoted here. The site also states that the official version is published by Thomson Reuters.)
Ask the body that would actually issue the permit, and be sure which one that is: on unincorporated county land A.R.S. 11-321(A) has already answered yes for anything over $1,000, while inside a city the answer lives in the local ordinance rather than in state law. Three protections travel with you either way — a prior owner's unpermitted work cannot be used to block your new permit except on public health or safety grounds, no transaction privilege tax or business licence may be demanded as a condition of issuance, and no permit may be denied over your choice of utility provider.
Based on the International Residential Code (IRC) and International Building Code (IBC) model codes. Every jurisdiction adopts a specific edition with its own local amendments — check your city’s permit page for the exact codes in force and their source citations.