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Keep the list of Western treaters that make and supply fire retardant treated lumber and plywood handy by downloading the Sources - Fire Retardant Treated Wood.

Exterior Fire Retardants

Exterior FR

Lumber and plywood treated with exterior fire retardant must withstand not only the dangers from fire, but also from exposure to the weather, water and other demanding conditions. Exterior fire retardants available today have a unmatched record of durability and fire protection.

To earn code acceptance as an exterior fire retardant, each formulation must pass rigorous testing to ensure the fire protection is durable. The accelerated weathering tests subject samples to the equivalent of 800-inches of rain over a 12-week period. Exterior fire retardants must also pass the same fire tests as required for interior applications.

Wood treated with exterior fire retardants are often used in commericial projects, for applications such as siding, decking, canopies, store fronts, facades and open-air roof systems. Exterior lumber is also used increasingly in locations prone to wildfires, where states my require exterior fire treatment for decking and outdoor construction in many wildland-urban interface areas.

There are two exterior fire retardants offered through Western treaters today:


A natural extension of Arxada's fire retardant products, FRX is used in exterior applications where other materials would transfer hear or allow fire to spread, where sprinkler systems cannot be easily installed or where fire protection is inadequate or not readily available.


Part of the SaferWood line of products, Thermex-FR is a safe and environmentally friendly formulate that renders wood safe from fire. Wood treated with Thermex-FR have passed strict fire and weathering tests and comply with all model building codes.

Like the interior formulations, exterior fire retardants have passed all code-required tests and are code compliant through an ICC-ES Evaluation Report for each formulation.

Exterior fire retardant lumber and plywood must be stamped with a detailed quality mark, that includes the statement "No increase in the listed classification when subjected to Standard Rain Test (ASTM D2898)."

Use the links above to download specification guides and other important information on FRX and Thermex-FR exterior fire retardant products.