Exterior Fire-X

Fire Retardant Treated Wood Products

Koppers Exterior Fire-X is an exterior grade, leach resistant (LR), fire retardant applied to timber by a pressure impregnration process. Exterior Fire X is a listed product in the 2012 UK Wood Protection Association Flame Retardants Manual.


Independent testing performed in accordance with industry standards has shown that Exterior Fire-X FRTW products exhibit enduring fire performance properties without compromising other critical engineering properties such as strength, durability, corrosivity and hygroscopicity.





Exterior Fire-X FRTW products are permitted for use in above ground interior or exterior applications where the adopted building regulations permit the use of wood products or fire retardant wood products, such as cladding, shingles, playground equipment, sheathing, joists etc. The specifier and/or end user is responsible for reviewing the test data on Exterior Fire-X FRTW products to determine whether they are acceptable for the intended end use. Exterior Fire-X treated timber has been shown to perform well in the standard fire retardant tests ASTM E84, BS 476 Part 7 and BS EN 13501-1. Treated timber has also maintained its fire retardant performance in the ASTM D2898 accelerated weathering test, used to approve leach resistant (LR), exterior grade fire retardant treatments.


Standards and Specification Information

Exterior Fire-X Fire Retardant Treated Wood products (FRTW) have been tested to BS EN 13501-1:2002 'Fire classification of construction products and building elements' and/or BS 476 Part 7 'Surface Spread of Flame of Products'.


These tests are commonly referred to as 'reaction to fire tests'. Reactions to fire tests are commonly called up in regulations in both the building and transport sectors. The classifications of flammability are A1, A2, B, C, D, E and F.


This table gives an overview of the classifications:


Koppers currently holds approvals for many of the most commonly specified species. Below is a list of just some of the approvals held.



Further materials are undergoing testing on a continuous basis, please contact us for a comprehensive list. Please check with Koppers for specific sizes tested and approval classification achieved. Exterior Fire-X treated wood can also be CE marked.

Exterior Fire-X is able to meet the requirements of HR (humidity resistant) treatment, DI (dry internal) and LR (leach resistant) specifications.



Exterior Fire-X is availbale as a service treatment through our treatment partner PTG Treatments.