Arizona

Statewide summary — confirm with your building department before designing

Termite risk is corrected from slight to moderate. Arizona sits in the compound moderate to heavy band of the IRC termite infestation probability map. The City of Flagstaff, the coolest populated part of the state, adopts moderate to heavy in its own amended design criteria table, and the Arizona Department of Agriculture describes a large number of subterranean termite colonies in desert areas. Heavy would be equally consistent with the IRC band, which pairs two levels; moderate is used here to match how other states in the same band are coded in this table. The remaining numbers on this row describe the Sonoran Desert lowlands and are wrong for the Colorado Plateau. Frost depth of 0 inches applies to Phoenix, Tucson and Yuma; the City of Flagstaff adopts a 30 inch frost line depth and Coconino County requires exterior footings 30 inches into undisturbed soil across most of the county, reduced to 24 inches in the Sedona, Marble Canyon and Greenehaven areas. Ground snow load of 0 psf likewise applies to the desert; Flagstaff adopts 60 psf and Coconino County tabulates 20 to 50 psf by area with an increase applied. Winter design temperature of 25 F matches neither Phoenix, which is warmer, nor Flagstaff, which adopts 4 F. Seismic design category B covers Phoenix and Tucson; Flagstaff adopts C and Prescott and Yuma also compute to C. The 115 mph wind speed is an ASCE 7 ultimate design wind speed for Risk Category II. Separately, the IRC requires a minimum footing depth of 12 inches below undisturbed ground everywhere, regardless of frost. Use the adopted design criteria table of your local jurisdiction. SNOW LOAD AUDIT 2026-08-12 (physical design data pass). Minimum and maximum both left NULL. Arizona has no statewide building code at all and publishes no ground snow load, minimum or maximum. This audit confirmed the mechanism rather than assuming the outcome. The statutory mechanism is A.R.S. 11-861. It places the power to adopt a building code with each county board of supervisors, for the unincorporated areas of a county that has adopted zoning, and it lets a board exempt areas zoned rural or unclassified from the code it adopts. What a board may adopt is limited to a building, electrical, plumbing or mechanical code published by a national code organisation, or the code already adopted by the largest city in that county, and a fire prevention code from a national organisation at least as stringent as the state fire code. There is no state building code sitting underneath that delegation for a county to fall back on, and municipalities adopt separately under their own authority. Colorado at least has a Division of Housing rule with numbers in it; Arizona does not even have that. Arizona's only state-level construction rules of general application are the Department of Housing and Office of Manufactured Housing rules in Arizona Administrative Code Title 4, Chapter 34. Section R4-34-102 adopts the 2018 editions of the International Building, Residential, Mechanical, Plumbing, Fuel Gas and Energy Conservation Codes and the 2017 National Electrical Code by reference, together with FEMA Publication 85. The chapter sets no snow load of any kind. The only occurrence of the word snow in it is inside the definition of permanent foundation in R4-34-101, in a clause requiring that a foundation transfer the vertical and horizontal design loads that wind, snow, frost, seismic or flood conditions could impose. No pounds per square foot value is attached to it anywhere in the chapter. Method note, recorded because it bears on how much weight the last paragraph carries. Both apps.azsos.gov and housing.az.gov return a Cloudflare managed challenge to direct requests, so Chapter 4-34 could not be downloaded and searched locally and no attempt was made to work around the challenge. It was instead read through a page-fetching service, twice, against two separately hosted copies of the same chapter, and both readings returned the same result: no snow load value, adoption of the 2018 I-codes by reference, and the single incidental mention of snow in the permanent foundation definition. No value on this row was changed by this pass, and everything the earlier audit recorded remains true and remains the right way to read this row. The stored ground snow load of 0 psf, frost depth of 0 inches, wind speed of 115 mph and seismic design category B describe the Sonoran Desert lowlands and are wrong for the Colorado Plateau. The local counterexamples already on this row stand: the City of Flagstaff adopts a 60 psf ground snow load, a 30 inch frost line depth and seismic category C, and Coconino County tabulates 20 to 50 psf by area with an increase applied and requires exterior footings 30 inches into undisturbed soil across most of the county, reduced to 24 inches around Sedona, Marble Canyon and Greenehaven. Those are city and county figures. Arizona itself publishes nothing, so no min or max could honestly be written here.