Arpit Jain 13 min February 24, 2026

Navigating Oregon's Wildland-Urban Interface (WUI) Building Codes: A Guide for Construction Professionals

As wildfire risk intensifies across the West, Oregon has implemented specific, mandatory building codes for construction in the Wildland-Urban Interface (WUI). For architects, engineers, and builders, understanding these requirements is critical for project approval, safety, and resilience. This guide breaks down the essential WUI regulations found in the Oregon Structural Specialty Code (OSSC) and Oregon Residential Specialty Code (ORSC), detailing how to determine applicability and comply with construction standards.

Direct Answer: Key WUI Code Requirements in Oregon

Oregon's WUI building codes apply to new construction and major alterations within designated wildfire hazard zones. Compliance is determined by a property's classification on the official Oregon Wildfire Risk Explorer map. The higher the risk (Low, Moderate, High, or Extreme), the more stringent the construction requirements.

These regulations are primarily located in ORSC Chapter 3, Section R327 for residential projects and OSSC Chapter 7A for commercial and other structures.

Key Construction Requirements:

• Determine Your Zone: First, use the Oregon Wildfire Risk Explorer map, managed by the Oregon Department of Forestry (ODF), to identify the property's specific WUI risk classification. This classification is the foundation for all subsequent requirements.
• Roofing: In High and Extreme risk zones, a Class A roof covering (e.g., asphalt composition, metal, concrete tile) is mandatory, tested per ASTM E108 or UL 790.
• Siding & Exterior Walls: Walls must be constructed of noncombustible or ignition-resistant materials. This includes materials like fiber-cement, stucco, brick, or products that have passed specific fire tests like ASTM E2707.
• Vents: All attic, foundation, and other ventilation openings must be protected against ember intrusion. This typically requires corrosion-resistant mesh with openings no larger than 1/8-inch or the use of a listed and approved ember-resistant vent.
• Windows & Glazing: Exterior glazing must be at a minimum dual-paned, with at least one pane being tempered glass. This applies to windows, skylights, and glass doors.
• Decks & Projections: Decking surfaces within 10 feet of the building in High/Extreme zones must be noncombustible, ignition-resistant, or meet performance criteria outlined in the code.
• Defensible Space: While regulated by the Oregon State Fire Marshal (OSFM) under Oregon Administrative Rules (OAR), defensible space is a critical, parallel requirement. It involves managing vegetation in zones extending up to 100 feet from the structure to reduce fuel loads. This is often reviewed and enforced by the local fire district in conjunction with the building permit.

Component	Common Requirement in High & Extreme WUI Zones	OSSC Reference	ORSC Reference
Roofing	Class A rated assembly	OSSC 705A.2	ORSC R327.5.2
Vents	1/8" mesh screening or listed ember-resistant design	OSSC 706A.2	ORSC R327.5.3
Exterior Walls	Noncombustible or ignition-resistant materials	OSSC 707A.3	ORSC R327.5.4
Windows/Glazing	Dual-pane with one tempered lite	OSSC 708A.3	ORSC R327.5.7
Decks	Ignition-resistant or noncombustible materials	OSSC 709A.3	ORSC R327.5.6

Context + Why This Topic Matters

The adoption of statewide WUI building codes, driven by Senate Bill 762 in 2021, represents a paradigm shift in Oregon's approach to wildfire resilience. Previously, WUI regulations were inconsistent and adopted only by a few local jurisdictions. Now, a unified, statewide standard based on the International Wildland-Urban Interface Code (IWUIC) is integrated directly into Oregon's building codes.

This topic is critical for design and construction professionals for several reasons:

• Permitting: Failure to address WUI requirements on construction documents is a common reason for plan review rejection in affected areas. Building departments are now mandated to enforce these provisions.
• Project Costs: WUI-compliant materials, such as Class A roofing, ember-resistant vents, and tempered glass, can significantly impact project budgets. These costs must be factored in during the early design and estimating phases.
• Design Limitations: The code places restrictions on exterior materials and certain architectural features. For example, the design of eaves, decks, and exterior trim must be carefully considered to minimize fire risk.
• Coordination Complexity: WUI projects require coordination between the architect/designer, the building department (enforcing OSSC/ORSC), and the local fire marshal or fire district (enforcing OSFM defensible space rules). Understanding the distinct but related responsibilities of each agency is key to a smooth project.

Common misunderstandings include assuming these codes are optional recommendations, confusing building hardening requirements with defensible space rules, or failing to check the official state map to confirm a property's WUI designation.

Detailed Answers to Each Question

How do I determine the applicable Wildland-Urban Interface (WUI) code requirements under the OSSC for a new residential subdivision near Ashland? What are the specific construction standards for roofing, siding, exterior glazing, and defensible space based on the local fire hazard severity zone map?

To determine the applicable WUI requirements for a project near Ashland (Jackson County), you must follow a systematic, map-based approach. The process begins with identifying the property's specific risk classification using the state-mandated tool, which then dictates the precise construction standards from the OSSC or ORSC.

The definitive first step is to locate the property on the Oregon Wildfire Risk Explorer. This official online map, maintained by the Oregon Department of Forestry, shows the boundaries of the WUI and assigns one of five risk classifications to properties within it: No Risk, Low, Moderate, High, or Extreme. The specific requirements are triggered by these classifications, with the most stringent rules applying to High and Extreme zones.

Once you have identified the risk classification, you can apply the specific construction standards found in the Oregon specialty codes. For a residential subdivision, the Oregon Residential Specialty Code (ORSC), Section R327 will apply to single-family dwellings, duplexes, and townhouses. For any non-residential buildings in the subdivision (e.g., a community center), the Oregon Structural Specialty Code (OSSC), Chapter 7A would apply.

Here are the specific construction standards based on a High or Extreme risk classification, which is common in the Ashland area:

1. Roofing (ORSC R327.5.2 / OSSC 705A.2):

• Requirement: Roofs must have a Class A fire rating. This is the highest rating for resistance to severe fire exposure.
• Materials: Common Class A materials include asphalt composition shingles, concrete or clay tiles, and most metal roofing systems.
• Standards: The assembly must be tested in accordance with ASTM E108 or UL 790. The entire roof assembly, including the covering, sheathing, and underlayment, must meet this standard.

2. Siding / Exterior Walls (ORSC R327.5.4 / OSSC 707A.3):

• Requirement: Exterior walls must be constructed with noncombustible materials or materials that demonstrate ignition resistance.
• Approved Materials:
  • Noncombustible: Brick veneer, stucco, stone, concrete, and metal siding.
  • Ignition-Resistant: Materials that have passed testing under ASTM E2707 (Standard Test Method for Determining Fire-Resistance of Exterior Wall Assemblies). Common examples include fiber-cement siding and treated wood products specifically rated for WUI use.
• Detailing: The code also governs exterior wall coverings to ensure no gaps or openings exist that would allow for ember intrusion.

3. Exterior Glazing / Windows (ORSC R327.5.7 / OSSC 708A.3):

• Requirement: Glazing in exterior windows, doors, and skylights must be, at a minimum, insulating-glass units with at least one tempered pane.
• Purpose: Tempered glass is much more resistant to breaking when exposed to the radiant heat of a wildfire, preventing a key entry point for fire and embers.
• Frames: Window and door frames and sashes must also be made of ignition-resistant or noncombustible materials. Vinyl is often permitted if it has internal metal reinforcement and meets specific performance criteria.

4. Defensible Space (OAR 837-110):

• Requirement: This is a property maintenance standard, not a building construction standard, but it is a mandatory companion to the building code. It is enforced by the Oregon State Fire Marshal (OSFM) and delegated to local fire agencies.
• Zones: Property owners in High and Extreme risk zones must create and maintain defensible space in three distinct zones around their homes:
  • Immediate Zone (0-5 feet): The most critical area. Must be completely free of flammable materials. Use noncombustible materials like gravel or pavers. No flammable vegetation.
  • Intermediate Zone (5-30 feet): Trees should be limbed up, and vegetation should be thinned to break up fuel continuity. Lawns should be kept mowed and irrigated.
  • Extended Zone (30-100 feet): Focus on reducing fuel loads, removing dead vegetation, and ensuring separation between trees and shrubs.
• Local Enforcement: For a project in Ashland, the local fire district (e.g., Ashland Fire & Rescue) will be the primary agency reviewing and inspecting for defensible space compliance, often as a condition of the building permit.

Are there specific building codes for building in a wildfire zone in Oregon?

Yes, Oregon has specific, mandatory, and statewide building codes for construction in designated wildfire zones. These regulations are not in a separate, standalone "wildfire codebook" but are fully integrated into the state’s primary building codes: the Oregon Residential Specialty Code (ORSC) and the Oregon Structural Specialty Code (OSSC).

These requirements were established by the Oregon legislature through Senate Bill 762 and became effective for projects permitted after their formal adoption. The technical provisions are largely based on the International Wildland-Urban Interface Code (IWUIC) and are designed to "harden" buildings against ignition from embers and radiant heat.

The key sections where these rules are located are:

• For Residential Buildings (One- and Two-Family Dwellings): ORSC Chapter 3, Section R327, "Wildland-Urban Interface Fire Area." This section details all construction requirements for homes in the WUI, from roofing and vents to decks and exterior walls.
• For Commercial and Other Buildings: OSSC Chapter 7A, "Materials and Construction Methods for Exterior Wildfire Exposure." This chapter mirrors the requirements in the ORSC but is formatted for the OSSC and applies to all buildings under its scope (e.g., apartments, offices, retail).

Applicability:

These codes apply to:

• New Buildings: All new structures constructed within a designated WUI zone (Low, Moderate, High, or Extreme risk) must comply.
• Additions and Alterations: The codes also apply to additions or substantial alterations to existing buildings in the WUI. The exact trigger for compliance on an existing building can depend on the scope and cost of the work, as defined in ORSC R327.1.3.

Compliance with these sections is verified by the local building official (the Authority Having Jurisdiction, or AHJ) during both the plan review and field inspection phases of a construction project.

Additional Supporting Sections

Navigating the Oregon Wildfire Risk Map

The Oregon Wildfire Risk Explorer is the sole official tool for determining if a property is subject to WUI building codes and defensible space requirements. It is not optional; its classifications are legally binding.

How to Use the Map:

1. Access the Portal: Visit the official Oregon Wildfire Risk Explorer website.
2. Enter the Address: Use the search bar to enter the full property address.
3. Review the Classification: The map will zoom to the property and display its risk classification (e.g., "High," "Extreme"). If the property is not in a colored zone, it is classified as "No Risk" and the WUI codes do not apply.
4. Document for Permitting: Take a screenshot or print a PDF of the map showing the property and its classification. This documentation is often required as part of the building permit application submittal to prove which WUI standards are being followed.

It is crucial to use the official state map, not third-party tools or general wildfire hazard maps, as only the ODF's map is tied to the legal requirements of SB 762.

Coordination Between Building Code and Defensible Space Requirements

A frequent point of confusion is the division of responsibility between building hardening and defensible space. While both are triggered by the same risk map, they are regulated and enforced by different agencies.

• Building Hardening (The Structure):

  • Regulations: OSSC Chapter 7A and ORSC Section R327.
  • Enforcing Agency: The local city or county Building Department.
  • Focus: Materials and assembly details of the building itself—roofing, siding, windows, vents, decks.
  • Verification: Plan review of construction documents and field inspections of the building during construction.

• Defensible Space (The Property):

  • Regulations: Oregon Administrative Rules (OAR) Chapter 837, Division 110, developed by the Oregon State Fire Marshal (OSFM).
  • Enforcing Agency: The OSFM or, more commonly, the local Fire Marshal or Fire District.
  • Focus: Management of vegetation and other flammable materials on the land surrounding the structure.
  • Verification: Often involves a site plan review and a final inspection of the property's landscaping and clearing, sometimes as a condition for the Certificate of Occupancy.

Best Practice: Engage both the building department and the local fire district early in the design process. Ensure the site plan submitted for the building permit also clearly demonstrates compliance with defensible space zones.

Common Mistakes and Misinterpretations in WUI Design

1. Ignoring Vents: Vents are a primary pathway for embers to enter a structure. Specifying standard vents instead of 1/8-inch mesh-protected or specialized WUI-rated vents is a common and dangerous error.
2. Non-Compliant Decking: Using standard wood decking within 5 or 10 feet of a building in a High/Extreme zone is a code violation. The code requires ignition-resistant, noncombustible, or heavy timber construction in this critical area.
3. Forgetting Under-Eave Construction: The area where the wall meets the roof is highly vulnerable. Fascia, soffits, and eaves must also be made of noncombustible or ignition-resistant materials.
4. Assuming "Fire-Retardant-Treated" Wood is Automatically Compliant: While FRT wood can be used, it must meet specific testing standards and be listed for exterior use to be compliant for siding or decking. Check the product's evaluation report.
5. Relying on Outdated Information: The WUI codes and risk map are new and subject to updates. Always verify requirements using the current, adopted versions of the OSSC/ORSC and the live Wildfire Risk Explorer map.

Cluster-Level FAQ Section

1. Do Oregon's WUI codes apply to remodels or additions? Yes, they apply to additions and substantial alterations. Per ORSC R327.1.3, if an addition increases the building's floor area by more than 50% or the alteration value exceeds 50% of the structure's value, the entire building must typically be brought into compliance. Smaller projects may only require the new work to comply.

2. What is "Class A" roofing? Class A roofing is a complete roof assembly that has passed the most stringent fire-resistance tests (ASTM E108 or UL 790). It demonstrates a high degree of resistance to fire penetration and spread from sources outside the building.

3. Who enforces defensible space rules in Oregon? The Oregon State Fire Marshal (OSFM) has rulemaking authority, but enforcement is typically delegated to the local fire chief, fire marshal, or fire district that serves the property.

4. Are sheds and garages subject to WUI building codes? Yes. Detached accessory structures greater than 200 square feet are generally required to comply with the same WUI construction standards as the main dwelling, especially concerning roofing and exterior walls.

5. Where can I find a list of approved WUI-rated building materials? The Oregon BCD does not maintain its own list. However, designers often reference product listings from the OSFM or the California Department of Forestry and Fire Protection (CAL FIRE), which maintains an extensive Building Materials Listing of WUI-rated products. Always confirm acceptance with the local building official.

6. How often is the Oregon Wildfire Risk Map updated? The map is subject to periodic review and updates by the Oregon Department of Forestry based on new data related to vegetation, climate, and weather. It's essential to check the live map for every new project.

7. Can I get an exemption from WUI building requirements? Exemptions are extremely rare. The code allows for "Alternate Materials, Design and Methods of Construction" (per OSSC 104.11), but any proposed alternative must be submitted to the building official with technical data proving it meets or exceeds the fire-protective qualities of the prescribed methods.

8. What if my property is on the border of two different risk zones? If a single property contains multiple risk classifications, the building code requirements for the highest-risk classification present on the property will typically apply to any structure built there.

9. Do these rules apply if I have a fire sprinkler system? While residential fire sprinklers (per NFPA 13D) are an excellent life-safety feature, they generally do not provide an exception or trade-off for the mandatory exterior building hardening and defensible space requirements in the WUI code.

10. What is "ignition-resistant" material? An ignition-resistant material is one that has been tested and shown to resist ignition or sustained burning when exposed to embers and small flames. The specific test protocol is defined in the building code (e.g., ASTM E2707). Examples include fiber-cement, treated wood, and certain composite products.