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Standards / IWUIC
International Wildland-Urban Interface Code
ICC model WUI code. It applies only where a jurisdiction adopts it. The 2024 edition is the model California amended into CWUIC. Oregon uses optional R327 instead of a statewide IWUIC mandate.
Covers: Ignition-resistant construction classes, defensible space, access, water supply, and material performance in mapped WUI areas where the model code is adopted.
Does not cover: Automatic effect in Oregon or California. Oregon uses optional local adoption of ORSC R327. California’s live book is CWUIC, not unmodified IWUIC.
The IWUIC is a model code. The International Code Council publishes it. It applies only where a jurisdiction adopts it. This page’s official URL is the 2024 title on ICC Digital Codes (IWUIC2024P1). That is a code path, not the ICC homepage and not a shop SKU.
Oregon’s wildfire construction path is ORSC R327, adopted city-by-city or county-by-county. California’s live book as of 1 January 2026 is CWUIC (Title 24 Part 7), not unmodified IWUIC and not Chapter 7A. Other sourced states differ in the asides below. Which edition governs a lot is the adopting ordinance’s answer, and each aside names the ordinance it read.
Why it matters
Embers and flame at the WUI are the exposure. A model book lets states start from one text. It is not adopted code until a legislature or a local ordinance says so. If you spec “IWUIC vents” on an Oregon lot, you may have named a book nobody adopted.
California did adopt a related book. BSC says CWUIC is based on the 2024 IWUIC, then amended. The amendments matter.
How the model book is arranged
ICC’s 2024 IWUIC preface describes an overlay code. It covers land use and buildings in designated wildland-urban interface areas, using both prescriptive and performance provisions.
| IWUIC chapter | What it decides |
|---|---|
| 1–2 | Scope, administration, definitions |
| 3–4 | WUI area designation, access, water, fire-protection plans. Chapter 4 points construction at IR 1, IR 2, or IR 3 |
| 5 | Special building construction. Class 1 / 2 / 3 ignition-resistant construction |
| 6 | Fire protection, including defensible space distances in Table 603.2 |
| 7 | Referenced standards |
Ignition-resistant construction in this book is a class of the building, not the same phrase as Oregon’s ignition-resistant material (an extended ASTM E84 / UL 723 run).
2024 IWUIC Class 1 is Section 504. Class 2 is 505. Class 3 is 506.
The paths
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Where a jurisdiction adopts IWUIC. Read that ordinance. Confirm the edition. Confirm which appendices. Then read Chapter 5 for the IR class Chapter 4 assigned. This site does not keep an IWUIC adoption map.
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Roofs in the 2024 model. 504.2 (Class 1) requires a Class A roof assembly tested to ASTM E108 or UL 790. 505.2 (Class 2) requires not less than Class A, or a noncombustible roof covering the code official accepts. 506.2 (Class 3) requires not less than Class B, or a noncombustible covering the code official accepts. Profile gaps at eaves must be firestopped or covered with ASTM D3909 cap sheet. That is the model. It is not Oregon’s Class B floor.
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Vents in the 2024 model. 504.10.1 is listed vents tested to ASTM E2886. 504.10.2 is a prescriptive path: openings not more than 144 square inches, covered with noncombustible corrosion-resistant mesh not more than 1/8 inch, or designed to prevent flame or ember entry. 504.10.3 keeps attic vents out of soffits and eave overhangs in that class. California CWUIC 504.10 is not a copy-paste of this pair.
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California. Spec CWUIC. Sections 505 and 506 are reserved. CBC Chapter 7A is the old search name.
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Oregon. Spec R327 where adopted. R327 versus CWUIC. Deschutes County will accept OSFM handbook products when they are on the drawings. That is not IWUIC adoption.
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Colorado. Spec the 2025 Colorado Wildfire Resiliency Code, not unmodified IWUIC. Class 1 and Class 2 hardening follow the fire-intensity map. Confirm the local adopting ordinance.
What people mix up
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Treating IWUIC as automatically in force. It is a model.
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Treating CWUIC as unmodified IWUIC. California reserved 505 and 506. Vent section numbering looks similar and is not identical.
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Treating IWUIC “ignition-resistant construction Class 1” as Oregon ignition-resistant material. Different documents.
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Using the ICC homepage as the code citation. The title path is
/content/IWUIC2024P1. The ICC shop card is a catalog page for print and PDF. -
Importing IWUIC 504.10.3 “no soffit vents” onto an Oregon R327 job without reading R327’s eave-vent rule.
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Calling FireApproved the adopting body. We are not.
How to check
Ask which book the building official adopted, and which year. If the answer is IWUIC, open the Digital Codes title and the adopting ordinance. If the answer is CWUIC, leave this page. If the answer is R327, leave this page.
If you spec a listed vent or roof model as a performance path, confirm the model on the listing. How to read a listing.
Limits
This page does not host the IWUIC text. It does not keep an IWUIC adoption map. ICC’s own adoption charts are incomplete by ICC’s note. Colorado’s live book is the CWRC, cited in Where this differs. It does not decide Oregon, California, or Colorado jobs. FireApproved is not an AHJ.
Related records
CWUIC is California’s amended book. Chapter 7A is the old California search name. ASTM E2886 is the vent test method 504.10.1 names.
Sources
- 2024 International Wildland-Urban Interface Code (ICC Digital Codes title)
- 2024 IWUIC Chapter 5 (ICC; IR classes and 504.10 vents)
- 2024 International Wildland-Urban Interface Code (shop) (ICC; catalog page for print and PDF, not the official reader)
- 2025 Title 24 California Code Changes (California Building Standards Commission; CWUIC based on 2024 IWUIC)
- 2025 California Wildland-Urban Interface Code (ICC / California)
- Home hardening and wildfire hazard mitigation (Oregon Building Codes Division)
- 2023 ORSC Section R327 amendment (Oregon Building Codes Division)
- 2025 Colorado Wildfire Resiliency Code (Colorado Division of Fire Prevention and Control)
- Ordinance 20250410-041 Wildland-Urban Interface Code (City of Austin; 2024 IWUIC with local amendments, effective 10 July 2025)
Does IWUIC apply in Oregon by default?
No. Oregon’s wildfire construction path is ORSC R327, adopted city-by-city or county-by-county. That is not a statewide IWUIC mandate.
Is California CWUIC the same book as IWUIC?
No. BSC says CWUIC is based on the 2024 IWUIC, then amended. California reserved IWUIC Sections 505 and 506. Spec the adopted Title 24 Part 7, not the model PDF.
What are IR 1, IR 2, and IR 3?
2024 IWUIC ignition-resistant construction classes. Class 1 is Section 504. Class 2 is Section 505. Class 3 is Section 506. Hazard, water, and access in Chapter 4 point at those classes. California CWUIC keeps 504 and reserves 505 and 506.
Is the official URL a shop page?
No. The official URL is ICC Digital Codes for the 2024 IWUIC title (IWUIC2024P1). A free account may be required to read it. ICC also sells a print and PDF catalog page. That catalog is not this URL.
Does Washington use IWUIC statewide today?
No. WAC 51-55-003 is reserved. RCW 19.27.560 adopts named Class 1 rules only upon completion of DNR hazard maps. Counties may adopt IWUIC locally now. See Washington WUI code status.
Did Kittitas County, Washington adopt IWUIC locally?
Yes. KCC 20.10 adopts the current IWUIC, with Appendices B and C, and designates all unincorporated areas as WUI. WAC 51-55 remains reserved statewide.
Does Nevada use IWUIC statewide as a construction book?
No. NAC 477.281 adopts the 2018 IWUIC including Appendices A and B. NAC 477.283 then deletes Chapter 5. Locals may adopt more stringent rules. See Nevada WUI code status.
Does Utah use 2024 IWUIC statewide today?
No. Current 15A-2-103 adopts the 2006 Utah Wildland Urban Interface Code for local adoption. The 2024 IWUIC is effective 1 January 2027. See Utah WUI code status.
Does Idaho adopt IWUIC statewide?
No. Idaho Code 39-4109 adopts IBC, the Idaho residential code, energy, and IEBC. IWUIC is not on that list. Locals may still adopt a WUI overlay. See Idaho WUI code status.
Does Montana require IWUIC on every lot?
No. ARM 24.301.181 adopts the 2021 IWUIC with Chapter 4 and Section 602 deleted. Locals that enforce IBC or IRC may elect to enforce it and must then map WUI areas. See Montana WUI code status.
Does Arizona require IWUIC statewide?
No. A.R.S. 11-861 lets a county adopt a current wildland-urban interface code. That is optional. See Arizona WUI code status.
Did Clark County, Nevada adopt 2024 IWUIC?
Yes, locally. Ordinance 5320 adopts the 2024 IWUIC with Appendices A, B, and C, effective 1 January 2026. NAC 477.283 still deletes Chapter 5 statewide. That is Clark County’s book, not Nevada’s.
Did Washoe County adopt IWUIC Chapter 5?
Yes, locally. Washoe County Code 100.100.10 (Ord. 1736, effective 1 July 2025; 2024 editions required for submittals on or after 1 January 2026) adopts the 2024 IWUIC, Chapter 5 only. NAC 477.283 still deletes Chapter 5 statewide.
Does Boise use statewide Idaho IWUIC?
No. Idaho does not adopt IWUIC statewide. Boise’s 2018 IFC amendments add Chapter 41 WUI construction, including Class A roofs for IR1. Confirm the overlay with the fire code official.
Did Taylorsville, Utah adopt 2024 IWUIC?
No. Ordinance 25-15 adds 15.08.060, which adopts the Utah Wildland Urban Interface Code as a construction code, effective no later than 31 December 2025. 15A-2-103 currently names the 2006 book. The 2024 IWUIC is not in force until 1 January 2027.
Did Salt Lake City adopt 2024 IWUIC?
No. Salt Lake City Code 18.44.010.B (Ord. 68-25, 2025) adopts the Utah Wildland Urban Interface Code as adopted by 15A-2-103, on property shown on the Salt Lake City Wildland Urban Interface Map. 15A-2-103 currently names the 2006 book. The 2024 IWUIC is not in force until 1 January 2027.
Did Prescott, Arizona adopt 2024 IWUIC?
Yes, locally. Prescott City Code 6-2-1 adopts the 2024 IWUIC by reference through Resolution 2026-1983, with Ordinance 2026-1943 recorded May 12, 2026. Section 302 declares the entire city WUI, while City GIS and predictive modeling assign the risk class. That is Prescott's book, not Arizona's. Confirm the project and class with the code official.
Did Teton County, Wyoming adopt 2024 IWUIC?
Yes, locally and separately. The County resolution applies only on unincorporated lands, adopted 7 January 2025 and effective 1 February 2025. Town Ordinance 1416 applies across Jackson’s corporate boundary, adopted 16 December 2024 and effective 1 January 2025. Confirm the exact authority and project with Jackson Hole Fire/EMS.
Did Eagle, Idaho adopt 2024 IWUIC?
No. Eagle 7-1G-3 adopts the 2018 IWUIC including Appendices A and B inside the Ordinance 947 mapped overlay. The map depicts reach, while 2018 Table 503.1, the project type, and any City-approved Fire Protection Plan determine the applicable path. FireApproved models 15 conservative IR1/IR2/IR3 material rows but does not project the table's IR1 + N.C., Not Required, or Not Permitted outcomes. That is not Idaho statewide.
Did Santa Fe County adopt 2024 IWUIC?
No. Ordinance 2023-6 adopts the 2021 IWUIC in unincorporated Santa Fe County and deletes Chapter 5. That is the county’s book, not New Mexico’s.
Did Sedona adopt 2024 IWUIC?
No. Sedona Fire District adopts the 2018 IWUIC with local amendments. Sections 505 and 506 are deleted, so Class 1 construction is the overlay. That is the fire district’s book, not Arizona’s. Confirm with the fire code official.
Did Flagstaff adopt 2024 IWUIC?
No. Flagstaff 5-02-001-0001, effective 1 January 2020, still adopts the 2006 IWUIC and Appendices A through D. That is Flagstaff’s book, not Arizona’s.
Does New Mexico adopt IWUIC statewide?
No. 14.7.2 and 14.7.3 NMAC adopt the 2021 IBC and IRC. IWUIC is not that statewide book. See New Mexico WUI code status.
Does Texas require IWUIC statewide?
No. Local Government Code 214.212 adopts the IRC as the municipal residential building code. IWUIC is not that statute. See Texas WUI code status.
Does Wyoming require IWUIC statewide?
No. Council on Fire Prevention Chapter 1 incorporates 2024 IBC, IEBC, IFC, IMC, and IFGC. IWUIC is not on that list. See Wyoming WUI code status.
Did Austin adopt 2024 IWUIC?
Yes, as a local overlay. Austin 25-12-181 adopts the 2024 IWUIC and Appendices A through D with the deletions and amendments in 25-12-181 and 25-12-183. Ordinance 20250410-041 takes effect 10 July 2025. Class 1, 2, and 3 ignition-resistant construction definitions are deleted. Proximity Zones A, B, and C replace them. That is Austin’s book, not Texas’s.
Does Florida require IWUIC statewide?
No. F.S. 553.73(7) updates the Florida Building Code from IBC, IFGC, IEBC, IMC, IPC, IRC, NEC, and IECC. IWUIC is not on that list. See Florida WUI code status.