Glossary / wildland-urban interface
WUI, the wildland-urban interface
Where houses and wildland vegetation meet or mix. WUI is a land condition. It is not by itself a product listing.
The wildland-urban interface, WUI, is where houses and wildland vegetation meet or mix. It is a description of land, not a rule: a house is "in the WUI" because of what surrounds it, and what that obliges the owner to do depends on which document a state or city has attached to the map.
The codes that carry the name. The International Wildland-Urban Interface Code, IWUIC, is the model code; states and cities adopt it, amend it or write their own. California's live book since 1 January 2026 is the CWUIC, Title 24 Part 7, which replaced the Chapter 7A people still search for; it applies in mapped fire hazard areas, and how to read a FHSZ map is the way to find out whether a lot is in one. Colorado's 2025 Wildfire Resiliency Code and Oregon's R327, adopted city by city and county by county, are the other two books on this site; R327 versus CWUIC sets them side by side.
"WUI compliant" and "WUI approved". Neither phrase is a rule. California's OSFM handbook lists products by model, and its 2025 edition says listing is not a statutory mandate for most WUI products; a listed model is one path under CWUIC, beside tested assemblies and prescriptive recipes. Outside California no listing program is attached to the word at all. The Build hubs hold, part by part, what each adopted book asks for and which listed products match.
What being in the WUI does not decide. It does not decide the plants: defensible space and Zone 0 come from separate guidance and, in California, a separate law. It does not decide insurance: IBHS Wildfire Prepared and California Safer from Wildfires are designations and credits, not the map. The map says where the rules apply; the adopted book says what they are.
Questions
What does WUI mean?
Wildland-urban interface: the zone where houses and wildland vegetation meet or mix. It describes the land. The construction rules come from whichever code a state or city has adopted for it: IWUIC, California CWUIC, Colorado CWRC or Oregon R327.
What is a WUI map?
The map a state or city uses to say where its wildfire code applies. In California the Fire Hazard Severity Zone maps decide where CWUIC applies; other states and cities publish their own. The guide on reading a FHSZ map walks one.
What is a WUI compliant product?
A phrase, not a rule. In California a product listed by model in the OSFM handbook is one path under CWUIC, and OSFM's 2025 handbook says listing is not a statutory mandate for most WUI products. The adopted code names the paths; the Build hubs show which listed products match each.
Is my house in the WUI?
Only the map your state or city publishes can say. California's FHSZ maps decide CWUIC; Oregon's R327 applies where a city or county adopted it; the Place pages on this site hold the sourced instrument for each place we have opened, and say plainly where there is none.
Also called: WUI, wildland urban interface.
Related
- adopted code
- defensible space
- zone 0
- siding
- roofing
- vents
- iwuic
- cwuic
- cbc-chapter-7a
- How to read a CAL FIRE FHSZ map
- Oregon R327 versus California CWUIC
- Firewise USA site recognition
Where this term is used
- Arizona WUI code status
- ASTM E119 versus a WUI wall test
- Black Hills ponderosa is an island forest
- Building code upgrade coverage
- California AB 38 seller disclosure
- Char rate
- Clark County IWUIC over Nevada’s deleted Chapter 5
- Class A covering is not a bag of shingles