Fire-rated ThermoWood® species are here in North America
We’ve been working on this for a while, and now it’s official. In partnership with SaferWood by Chemco, Inc., BPWood’s ThermoWood® Ayous and ThermoWood® Nordic Pine treated with Thermex-FR earned a Class A rating on the 30-minute tunnel test ASTM E2768 after accelerated weathering ASTM D2898. Independent third-party labs ran the testing. These are the first ignition resistant ThermoWood® species options available in North America.
What “fire-rated” means in plain English
Ignition resistant: the wood is treated so it’s harder to ignite and flame spread is slowed.
Class A: the highest surface burning classification for wood products.
Exterior FRTW: Fire-Retardant Treated Wood that can be used outdoors under the most stringent building codes in North America.
How the fire testing works
ASTM E2768 (30-minute tunnel test): Treated wood is placed in a long tunnel. A controlled flame is applied at one end. Instruments track how far and how fast flames travel across the surface during 30 minutes of exposure. Class A confirms the board resisted flame spread at the highest level for this method.
ASTM D2898 (accelerated weathering): Boards go through water spray and heat cycles to mimic years of outdoor exposure before the fire test. Many products lose performance after this step. ThermoWood® Ayous and Nordic Pine maintained Class A after this sequence with SaferWood Thermex-FR.
WUI quick guide
What is the WUI? The Wildland-Urban Interface is the zone where buildings meet or intermingle with wildland vegetation. It is a focus area for wildfire risk reduction.
Why Exterior FRTW matters: The International Wildland-Urban Interface Code (IWUIC) allows fire-retardant-treated wood identified for exterior use as an ignition-resistant material under Section 503.2 when it meets the requirements of IBC 2303.2. This is a key pathway for cladding, soffits, decks, and similar applications in designated WUI areas.
State and local adoptions: Many jurisdictions reference WUI provisions. Examples include California CRC Chapter 7A for exterior wildfire exposure and Colorado’s 2025 Colorado Wildfire Resiliency Code for designated WUI areas. Always confirm with your local authority having jurisdiction.
What the codes mean
With Class A after weathering, and recognition as Exterior FRTW and ignition resistant, there is a clear path under the most stringent building codes in North America. That includes IBC, IWUIC, and state adoptions such as California CRC Chapter 7A and Colorado’s Wildfire Resiliency Code. Project acceptance varies by jurisdiction. Check with your local AHJ.
Where this can be used
Siding and cladding
Soffits and enclosed eaves
Porch ceilings
Decking
Fencing near buildings
Project acceptance varies by jurisdiction. Check with your local authority having jurisdiction. If you want the deep technical details on Thermex-FR, see SaferWood’s ICC-ES and QAI listings below.
Partners
BPWood supplies ThermoWood® to North America in partnership with LDCwood, a member of the International ThermoWood® Association. Learn more about BPWood ThermoWood and LDCwood.