Does Arizona's ADU law apply where I live?
Arizona's ADU rules cover cities and towns of more than 75,000 people under one statute and unincorporated county land under another, so a smaller city or town is bound by neither, and neither applies on tribal land or in the airport areas they exclude.
Arizona has two ADU statutes, not one, and which applies depends on who does the zoning where the lot sits.
The two statutes
- Cities and towns. Section 9-461.18 applies to "a municipality with a
population of more than seventy-five thousand persons", meaning a city or town that exercises zoning powers.1 The section does not say which population count is used. If a city is near 75,000, ask its planning department whether it treats the section as applying.
- Counties. Section 11-810.01 applies to counties, with no population
threshold in its text.2 A county's zoning covers unincorporated land, so this is the statute for lots outside city and town limits.
A city or town of 75,000 people or fewer sets its own zoning and is outside the city statute's threshold, so neither section binds it. Its own ADU rules are the ones that count.
Where neither applies
Both statutes exclude tribal land and land in the vicinity of a military airport or ancillary military facility. They also exclude land in the vicinity of commercially licensed, general aviation and public airports as the statutes describe it, with a 65-decibel noise test.12 The county statute also excludes property in a high noise or accident potential zone.2
What they don't change
Building codes, fire codes and public health and safety rules still apply. Neither a city nor a county may require an ADU to meet a commercial building code or to have a fire sprinkler.12 Counties keep their sensitive-area, wildfire, emergency access, drainage and flood rules, and can require a septic system to be adequately sized before an ADU is built.2 An ADU cannot go on top of a current or planned public utility easement without the utility's written consent.12
Who publishes this
Kyrax Developments is a BC Housing-licensed builder based in British Columbia. It publishes this page as a reference to Arizona state law. The page is not legal advice and not an offer of construction services in Arizona. The city or county planning department has the final word on any specific lot.
One question per page. The first sentence is the answer. When a figure changes, the page changes and the verified date moves. All answers.