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The IWUIC edition on the lot
The IWUIC year on the ordinance is a construction specification. It is not a synonym for “WUI code.” Flagstaff 5-02-001 still adopts the 2006 edition after the city moved its fire code to 2018. Prescott 6-2-1 now adopts 2024 with current local amendments. Spec the year, local application, risk class, and project trigger the building official names.
You are looking at a Flagstaff eave or a Prescott roof and asking whether “Arizona IWUIC” is one detail. Arizona has no statewide IWUIC book. A.R.S. 9-806 lets a city adopt a current WUI code. These two cities did, at different editions, with different local amendments. See Arizona WUI code status.
Why it matters
Embers enter at vents and under decks. A 2024 IWUIC note on a 2006 Flagstaff lot names the wrong book. In Prescott, the current year is only the first question: the City risk result maps extreme to IR1, high to IR2, and moderate to IR3, while project thresholds can exempt specified work from Chapter 5. The local application is the second question.
How it works
Flagstaff’s fire-code section, effective 1 January 2020, adopts the 2018 International Fire Code. The same section still adopts IWUIC, 2006 Edition, with Appendices A–D. An IFC update did not silently update IWUIC.
The city’s WUI requirements handout says Flagstaff adopted that 2006 book in March 2008. Class 1 ignition-resistant construction on that handout includes a non-combustible roof covering, noncombustible or heavy-timber eaves, Class A flame-spread walls or heavy timber, underfloor enclosed to grade, 144-square-inch vent openings with 1/8-inch mesh, and this location rule: attic ventilation openings shall not be located in soffits, in eave overhangs, between rafters at eaves, or in other overhang areas.
The same Flagstaff code’s IWUIC 504.10 amendment also lets the official approve fascia or soffit vents with 1/8-inch mesh, located as far from the exterior wall as practical. That exception is the official’s. Do not treat the handout and the exception as the same sentence. Ask.
Prescott 6-2-1 now adopts the 2024 IWUIC through Resolution 2026-1983, with Ordinance 2026-1943 recorded May 12, 2026. Current Section 302 declares the entire incorporated city a WUI. That citywide declaration does not select a construction class: City predictive modeling and GIS assign the risk severity, then 503.1 maps extreme to IR1, high to IR2, and moderate to IR3.
Prescott rewrites 505.2 and 506.2 so both Class 2 and Class 3 roofs require a Class A assembly tested to ASTM E108 or UL 790. Section 506.5 sends Class 3 vents to the Class 1 prescriptive or tested paths. New Section 506.6 adds Class 3 eave, soffit, and fascia-back protection alternatives. Sections 101.5 and 105.3 separately define project thresholds and exemptions; a ZIP cannot decide those facts.
Both opened cities amend Chapter 5. They do not delete it. That is the opposite cut from what deleting IWUIC Chapter 5 actually removes.
The paths
| Detail | Flagstaff (2006 IWUIC, opened) | Prescott (2024 IWUIC, opened) |
|---|---|---|
| Model year named | 2006, still named after the 2018 IFC adoption | 2024, adopted by reference in 2026 |
| Geographic reach | City/local overlay and handout; confirm the parcel | Entire incorporated city declared WUI; City GIS still assigns risk severity |
| Construction classes | Opened Class 1 handout and local amendments | Extreme → IR1; high → IR2; moderate → IR3 |
| Roof path | Opened local covering language differs from the current model | Class A ASTM E108 or UL 790 assembly in Classes 1, 2, and locally amended Class 3 |
| Class 3 eaves | Not projected from the opened Flagstaff material | Prescott 506.6 adds eave, soffit, and fascia-back protection alternatives |
| Project thresholds | Confirm with Flagstaff | 500-square-foot and 25-percent thresholds plus listed exemptions require project review |
| Chapter 5 | Amended, not deleted | Amended, not deleted |
- Name the year. Ask which IWUIC edition is adopted.
- Read the local amendments. The year is not the whole book.
- No statewide Arizona IWUIC. Spec the city ordinance or ordinary IBC/IRC.
- Harden anyway. IBHS is a designation, not adopted code.
What people mix up
- Treating “IWUIC” as one construction chapter. The year matters.
- Treating Flagstaff’s 2018 IFC as a 2018 or 2024 IWUIC.
- Copying Prescott’s 2024 material paths onto a Flagstaff 2006 project, or the reverse.
- Treating Prescott’s whole-city WUI declaration as if it also selected IR1, IR2, or IR3 for the parcel.
- Treating either city as Arizona statewide.
- Importing Oregon R327 or California CWUIC onto an Arizona drawing.
- Confusing Flagstaff’s “Class A flame spread” wall language with a Class A roof assembly. See covering versus assembly.
How to check
- Ask the building official which IWUIC edition is adopted, and which map it uses.
- If Flagstaff, open 5-02-001 and the WUI handout. Confirm whether soffit vents need the 504.10 exception.
- If Prescott, open 6-2. Read 302, 502, 503.1, 505.2, 506.2, 506.5, 506.6, and the project thresholds in 101.5/105.3.
- This site does not read your parcel.
Limits
This page quotes the opened Flagstaff code and handout and the current opened Prescott chapter. It does not reproduce unmodified model-book text that the local pages do not publish. It does not decide Phoenix, Tucson, or Sedona. It does not classify a parcel or project.
Related records
- Arizona WUI code status
- Flagstaff and Prescott place records
- What deleting IWUIC Chapter 5 actually removes
- Mesh versus listed vents
- Fire apparatus access
Questions
Does the IWUIC year on the ordinance actually change the house?
Yes, where the local amendments differ. Flagstaff still names the 2006 IWUIC in 5-02-001 after it adopted the 2018 International Fire Code. Prescott 6-2-1 now names the 2024 IWUIC; its current amendments declare the entire city WUI, assign IR1/IR2/IR3 through City risk modeling, require Class A roofs in Classes 2 and 3, and add Class 3 eave protection. Confirm the project and risk class with the building official.
Did Flagstaff keep 2006 IWUIC when it updated the fire code?
Yes. 5-02-001-0001, effective 1 January 2020, adopts the 2018 IFC and still adopts the IWUIC 2006 Edition with named appendices. An IFC year is not an IWUIC year.
Can I spec 2024 IWUIC vents on a Flagstaff or Prescott lot?
Prescott now adopts the 2024 IWUIC with local amendments; Flagstaff still names 2006. That does not make every 2024 model detail applicable to every project. Ask the official for the edition, local amendment, City risk class, and project trigger. Arizona has no statewide IWUIC book.
Do both cities keep Chapter 5 construction?
The opened texts amend Chapter 5; they do not delete it. That is the opposite cut from Santa Fe County 9.H and from Nevada’s State Fire Marshal path. Confirm the current ordinance.
Is this Arizona’s book?
No. A.R.S. 9-806 lets a city adopt a current WUI code. Flagstaff and Prescott did, at different editions. Prescott's 2024 adoption is not Phoenix and not a statewide mandate.