3 Steps to Wildfire Code Compliance withIgnition Resistant ThermoWood®
Leading Through Disruption
Wildfires are more frequent and more devastating. Building codes are changing rapidly to adjust to this new reality with ever stricter requirements.
In this environment, Class A has taken on new meaning while terms, like WUI-approved or WUI-certified, Fire-treated (slang), Fire-resistant, and Ignition-resistant, are tossed around and applied without proper vetting or understanding.
The only way for real wood to remain relevant is to continue to meet demanding aesthetic and performance expectations while simultaneously delivering on higher standards of compliance.
At BPWood, we're working with LDCwood and SaferWood™ to bring genuine ThermoWood® to North America. Our Ayous and Nordic Pine products have passed the full ASTM testing sequence required for exterior use in all Wildland Urban Interface (WUI) areas in the United States and Fire Hazard Severity Zones (FHSZ) in California.
#1 – Clarity is Confidence: Understand Testing.
The most common example of an Ignition Resistant material is Exterior-rated FRTW. For wood to qualify as Ignition Resistant and approved for exterior use as a stand-alone product, it needs to clear a specific set of hurdles.
The Non-Negotiables
Fire Retardant Treated Wood per IBC 2303.2 — This is the baseline definition. If a product doesn't meet this standard, then it’s not compliant.
ASTM E2768 or the "30-minute E84 test," is an extended-duration fire-test-response standard measuring the surface burning characteristics of building materials. It extends the standard 10-minute ASTM E84 test to 30 minutes to evaluate materials (like treated wood) that must limit flame spread, requiring a maximum flame spread index of 25, with no evidence of progressive combustion, for 30 minutes.
ASTM D2898 or the “800-inch rain test” is an accelerated weathering procedure for fire-retardant-treated wood, simulating 800 inches of rain over 12 weeks—approximately the same amount of weathering the wood would experience in 10 years. It is primarily used for exterior-use materials to test for chemical leaching.
FSI* (Flame Spread Index): 0-25 = Class A.
SDI* (Smoke Development Index): 0-450 = Class A.
*SaferWood with Thermex-FR produces an FSI less than 25 with SDI less than 55 for all treated species. An extremely high level of performance when compared to other ignition-resistant and/or non-combustible materials.
The ASTM Requirement
Ignition Resistant Exterior FRTW is required to pass the rigorous ASTM E2768 after D2898 Accelerated Weathering per IBC/IWUIC requirements. This is NOT an either/or situation. Passing only the 30-minute burn test does not approve FRTW for exterior use. ASTM E2768 and D2898 must be run in sequence— surface burning after weathering—to meet code compliance as Ignition Resistant Exterior FRTW.
Without the weathering component, FRTW use is restricted to interior installations, or the product must be part of a specific tested assembly with additional protective materials. This distinction is everything when you're specifying siding, soffits, or decking for a project in a WUI-designated area or FHSZ.
#2 - California's 12-7A Path: Useful, But Limited.
California does offer an alternative compliance path for exterior wood through SFM 12-7A testing. These are assembly-based evaluations—12-7A-1 for walls, 12-7A-4 for decks—that allow untreated combustible wood to be used when installed as part of a specific tested system. Products that pass 12-7A are compliant within California's WUI areas and Fire Hazard Severity Zones. But there are constraints:
12-7A Limitations:
Profile specific — Only the exact board profile tested in the assembly is approved. Different width or edge detail requires separate testing.
Dimension specific — Different thicknesses also require separate testing.
Assembly specific — Different underlayment, fasteners, or framing spacing can void the approval requiring new testing.
California only — 12-7A doesn't satisfy WUI codes outside California; SFM 12-7A is a California Building Code standard.
Lab approval matters — The testing agency must be authorized by California's State Fire Marshal. Tests from unapproved labs don't count.
The Flexibility Trade-Off
Ignition Resistant Exterior FRTW (like our SaferWood™-treated ThermoWood®) is compliant everywhere the IBC and IWUIC have been adopted—all 50 states, including CWUIC-California Wildland Urban Interface Code, and exceeds SFM 12-7A as an Ignition Resistant material: Any profile. Any dimension. Any application. One product, universal compliance.
#3 – All or Nothing: Check Every Box.
When we partnered with SaferWood™ to bring Ignition Resistant ThermoWood® to North America, BPWood made a strategic decision: we'd only work with the best, do full testing for unquestionable compliance, and check every box, or we wouldn't do it at all.
Our ThermoWood® Ayous and Nordic Pine treated with SaferWood’s Thermex-FR® achieved Class A surface burning and smoke development after ASTM E2768 and D2898 at independent third-party quality assurance providers. Reports issued by International Code Council Evaluation Service [ICC-ES] and QAI Laboratories.
That means our products are:
Ignition Resistant per code definitions
Exterior FRTW approved for outdoor stand-alone use
Class A rated after weathering and extended surface burning
Code Compliant with IBC, IWUIC, CWUIC, SFM Chapter 7A, and Colorado's Wildfire Resiliency Code
Multiple-use Installation as siding, cladding, soffit, decking, fencing—any exterior application
Flexible on profile and dimension without needing new tests.
Verify the Claims
Can you provide the full third-party evaluation report?
Which accredited agency performed the testing? (Look for ICC-ES, QAI, Intertek, or UL)
Does this product have both ASTM E2768 AND D2898 results for exterior approval?
Is the testing lab approved by the relevant state authority for my project?
What profiles and dimensions are covered under this evaluation?
What to Compare
Get the evaluation report. Match it against the code requirements in your project's jurisdiction. Look for:
Both fire AND weathering test results
FSI and SDI numbers in Class A range
Clear statement of exterior use approval
Testing agency on the approved list for your state
Frequently Asked Questions
What's the difference between "fire rated" and "ignition resistant"? Fire rated is often used when talking about wood but generally misunderstood. It does not accurately describe Exterior-rated FRTW. Fire-resistant or fire-resistance is applicable when discussing a fire-rated assembly such as 1 & 2-hour wall assemblies with specific components. It is not applicable when discussing the surface burning and smoke development characteristics of Exterior-rated FRTW such as siding, decking, soffit, etc., which has been evaluated as an Ignition Resistant stand-alone product.
Our project is in Colorado. Do California rules apply? Colorado has its own Wildfire Resiliency Code (CWRC), and Ignition Resistant Exterior FRTW satisfies it. Because the IBC has been adopted in all 50 states, products meeting the full exterior FRTW standard are compliant nationwide in WUI-designated areas. California's 12-7A path is California-specific, but proper exterior FRTW travels far and wide.
Can the same ThermoWood® species be used in any profile or dimension? Yes—that's one of the key advantages of Ignition Resistant Exterior FRTW over assembly-tested products. Once a species is tested and approved (like our Ayous and Nordic Pine), it can be milled to any profile and dimension without requiring new testing.
Why does it matter which lab performed the testing? State building authorities maintain lists of approved testing agencies. A test performed by an unapproved lab doesn't satisfy code requirements in that jurisdiction. For California projects, the lab must be on the State Fire Marshal's approved list. Always verify before you specify.
A product says it’s "WUI approved." How do I verify that? Ask for the evaluation report. Verify both ASTM E2768 and D2898 as part of the evaluation report. Confirm evaluation reports are from accredited US agencies such as ICC-ES, QAI, UL, etc. Check that the testing agency is approved in your jurisdiction. If any of these are missing, dig deeper, ask more questions, or seek advise from code compliance experts.
What applications are covered by BPWood's ThermoWood®? Our ThermoWood® Ayous and Nordic Pine treated by SaferWood™ are approved for exterior use as siding, cladding, soffits, enclosed eaves, porch ceilings, decking, and fencing near buildings. Because it's a stand-alone Ignition Resistant Exterior FRTW product, it doesn't require specific assembly components—giving you design flexibility across multiple design and build applications.
Let’s Talk!
Have a project in a WUI area or FHSZ? Want to know more about ThermoWood® Ayous and Nordic Pine? Reach out. We're here to walk you through the process.
Contact BPWood:
— Email: trader@bpwood.com
— Phone: +1 (250) 493-9339
Wood products are renewable and sustainable. A safer built environment is our shared goal. We're here to make sure the materials you specify are rigorously tested, fully documented, and genuinely code compliant.
Since 1981, SaferWood™ with Thermex-FR® by Chemco Inc., has been the gold standard for Ignition Resistant Exterior FRTW. SaferWood produces Thermex-FR, their non-toxic and nonhazardous exterior-rated fire retardant, on-site at their treatment facility in Ferndale WA. Wood treated by SaferWood with Thermex-FR is approved for use in all WUI designated areas across the United States and California’s Fire Hazard Severity Zones (FHSZ) including Very High. SaferWood’s one-time permanent pressure-treatment protects property and saves lives with Real Wood. Made Safer. ©