A.R.S. 11-861: How Arizona Counties Adopt Building Codes for Rural Land

If you build on unincorporated land in Maricopa or Pinal County instead of inside a city, your building code comes from the county. A.R.S. 11-861 is where the county gets that authority. The section lets a county board of supervisors adopt building codes for the rural areas it zones. It also fences off several things the county cannot do. It is the county counterpart to the city code powers, with extra provisions aimed at fire and pools.

What the section lets a county do

A county board of supervisors can put a building code in force across the unincorporated land it zones.

the board of supervisors may adopt and enforce, for the unincorporated areas of the county so zoned, a building code and other related codes

Like a city, a county adopts these codes by reference rather than reprinting them. It names an edition and adds local amendments. Maricopa County, for example, adopted the 2018 International Building Code and the 2018 International Residential Code in a Board of Supervisors vote on August 17, 2022. The county took on the 2017 National Electrical Code and regional amendments at the same time. Those model codes are copyrighted. That is why the county adopts them by reference and keeps a copy on file instead of posting the full text. If your lot sits on unincorporated county land, that adopted code, not a city's, is what your home is designed and inspected to.

The fire-sprinkler limits

11-861 carries the same sprinkler protection that cities operate under, plus a second clause closing an obvious workaround.

shall not adopt a code or ordinance ... that prohibits a person or entity from choosing to install or equip or not install or equip fire sprinklers in a single-family detached residence or any residential building that contains not more than two dwelling units

A county cannot force sprinklers on your single-family home or small duplex. The same pre-December 31, 2009 grandfather exception from the city statute applies here too. The section then goes further, to fire apparatus access roads. Those are the routes a fire truck uses to reach a house. A county cannot turn an access-road rule into a backdoor sprinkler mandate, and the statute preempts any county rule that tries. So a long rural driveway can trigger access and turnaround standards. It cannot trigger a sprinkler requirement dressed up as a road rule.

Pool gates, fire watch, and refrigerants

The section also reaches a few specific building details that come up on rural custom homes:

• Pool barrier gates. From and after December 31, 2014, a county code can reach the locking devices on pool barrier gates. It applies to semipublic pools built or heavily remodeled after that date. That sits alongside the statewide pool-fence law, and it matters if your project includes a shared or community pool.
• Fire watch. When a fire watch is required during construction, a building's own employees can stand it. They have to be able to reach the fire department and keep up constant patrols.
• Refrigerants. A county cannot ban an HVAC refrigerant that federal Clean Air Act rules list as acceptable. The equipment still has to be listed and installed to those use conditions. That keeps a newer, lower-impact refrigerant out of reach of a local ban as the HVAC trade moves to them.

What this means for you

Building outside city limits does not mean building without a code. On unincorporated land in Rio Verde or the desert edges of Cave Creek, the county's adopted code and permit process apply. 11-861 is the source of that authority. Your rural home is held to the county's adopted edition of the residential code. The county cannot make you sprinkler a single-family house, and it cannot do it through a road rule. It also cannot block an EPA-approved refrigerant in your air-conditioning. Our page on Maricopa County residential building permit requirements covers what the county wants on a rural build.

How this connects to the rest of the law

11-861 is the county mirror of two city statutes: the code-adoption power in A.R.S. 9-802 and the sprinkler limit in A.R.S. 9-807. Its pool-gate clause works with the statewide pool-barrier rule in A.R.S. 36-1681. If your rural parcel is in unincorporated county land, the county ADU law also runs off county zoning. The adopted code is usually the International Residential Code and International Fire Code, enforced by the county as your authority having jurisdiction (AHJ). For applied questions, see what you need to build on rural land in Rio Verde and does a hot tub or spa need a pool barrier in Arizona.

Full text and source

Read the current section, with all of its fire and utility subsections, on the legislature's site: View A.R.S. 11-861 on azleg.gov. FindLaw carries the same text at codes.findlaw.com, and Maricopa County lists what it adopted under this authority on its ordinances and codes page.

A county writes its own amendments and picks its own adopted edition. So a parcel straddling the Scottsdale line and unincorporated county land can end up under two different code stacks. Settle which jurisdiction your lot actually sits in before a designer draws anything.