Exterior Fire-X is pressure-impregnated fire-retardant lumber and plywood that provides tested fire protection for applications directly exposed to the weather or high humidity, outdoors as well as indoors.



  • Exterior decks
  • Balconies
  • Stairways
  • Siding
  • Scaffolding
  • Moulding
  • Trim
  • Open-air roof systems
  • Stables
  • Soffit
  • Fascia
  • Roof sheathing

Exterior Fire-X lumber and plywood offers the workability and versatility of wood as well as the fire-safety and insurance advantages of non-combustible materials.

Balconies and exterior walls constructed of Exterior Fire-X may be considered non-combustible by some building codes.

Exterior Fire-X siding is often accepted as an alternate for non-combustible siding, and exterior stairs constructed of Exterior Fire-X are generally accepted as non-combustible.

Exterior Fire-X treated roof systems including roof supports, trusses, and decking may often be substituted for non-combustible construction in open warehouses, storage sheds, and other structures with no penalty in the insurance rates or the building code classification of the structure.

Exterior Fire-X lumber and scaffold plank for temporary structures in construction projects may help reduce the cost of builders risk insurance.

The Specifier should evaluate the acceptability of the product for each application.

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  • Permits use of wood under restrictive codes
  • Thoroughly strength tested
  • Can be used outdoors or indoors
  • Reduces insurance rates
  • Non-corrosive
  • Each piece identified with UL classification mark
  • Kiln drying monitored by Timber Products Inspection Inc.
  • No halogens or sulfates
  • Optional blue color coded
  • Can be painted or stained
  • Approved for use in nuclear power plants

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Code Acceptability

Each piece of Exterior Fire-X lumber and plywood bears the Underwriters Laboratories label as required by building codes.

Exterior Fire-X fire retardant treated lumber and plywood meets or exceeds the requirements of the following agencies:

  • Military Specification MIL-L-19140
  • International Code Conference (ICC)
  • Building Officials and Code Administrators (BOCA)
  • Southern Building Code Congress International (SBCCI)
  • International Conference of Building Officials (ICBO)
  • Insurance Service Office (ISO)
  • American Nuclear Insurers
  • Nuclear Mutual Limited

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Code Compliance

Exterior Fire-X meets the flame spread requirement of all building codes which is 25 or less, as determined by Underwriters Laboratories in the extended 30 minute duration of ASTM E-84, “Standard Test Method for Surface Burning Characteristics of Building Materials.” Each piece of treated wood bears the Underwriters Laboratories Classification mark identifying it as being produced under its Classification and Follow Up Services.

Exterior Fire-X should not be confused with fire-retardant surface coatings, because test requirements and code definitions are entirely different for each. Exterior Fire-X is pressure impregnated and carries a flame spread rating derived by Underwriters Laboratories in the 30 minute ASTM E-84 flame spread test, while coatings are sprayed, brushed or rolled on the surface and tested for only 10 minutes. Fire retardant coated wood is superficially protected at best, and it does not meet code requirements for structural uses.

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Exterior Fire-X can be painted or stained much like untreated wood. Water repellent preservative finishes are recommended for exterior applications directly exposed to the weather.

Coating systems should first be tested on sample material and exposed to actual use conditions to determine if the desired effect can be obtained.

Marks left by drying sticks may appear on both sides of lumber and plywood. Stick marks may be minimized by special order. This must be specified when placing the order, and is recommended for exterior siding.

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Wood Siding

Exterior Fire-X treated wood siding combines the economy and natural beauty of wood siding with the insurance and safety advantages of fire resistant siding.

It is used to meet restrictive fire performance criteria and/or to reduce insurance rates.

Exterior Fire-X treated siding is often accepted as an alternate for non-combustible siding.

It is available in 303 plywood sidings and various lap siding patterns in cedar, pine, and fir.

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Exterior Fire-X Blue

Exterior Fire-X Blue is color coded with a pressure-applied blue stain for easy identification. It has the same fire performance characteristics, ratings and approvals as Exterior Fire-X.

Exterior Fire-X Blue is widely specified by government agencies and is used in the nuclear construction and ship-building industries.