Put ExteriorFireX to work in your next project.

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


ExteriorFireX meets the flame spread requirement of all building codes which is 25 or less, as determined by UL Solutions in the extended 30 minute duration of ASTM-84 (UL 723), “Standard Test Method for Surface Burning Characteristics of Building Materials.” Each piece of treated wood bears the UL Solutions Classification mark identifying it as being produced under its Classification and Follow Up Services.

ExteriorFireX should not be confused with surface coatings, because test requirements and code definitions are entirely different for each.

ExteriorFireX is pressure impregnated and carries a flame spread rating derived by UL Solutions in the 30 minute ASTM E-84 (UL 723) flame spread test, while coatings are sprayed, brushed or rolled on the surface and tested for only 10 minutes. Coated wood does not meet code requirements for structural uses.

Design & Construction Guide

Safer by design. Sustainable by nature.

This is your guide to designing and building with Hoover’s code compliant, pressure impregnated, kiln dried, fire-retardant-treated lumber and plywood products.


-Permits use of wood under restrictive codes

-Thoroughly strength tested

-Can be used outdoors or indoors

-Reduces insurance rates


-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


ExteriorFireX Specs

A detailed rundown of everything related to our top of the line fire-retardant-treated lumber and plywood for enclosed structural applications.


-Exterior Decks







-Open-air roof systems




-Roof sheathing

ExteriorFireX fire-retardant-treated lumber and plywood offers the workability and versatility of wood as well as the fire-safety and insurance advantages of noncombustible materials.
Balconies and exterior walls constructed of ExteriorFireX may be considered noncombustible by some building codes.
ExteriorFireX fire-retardant-treated wood siding is often used in lieu for noncombustible siding, and exterior stairs constructed of ExteriorFireX are generally accepted as noncombustible.
ExteriorFireX fire-retardant-treated roof systems including roof supports, trusses, and decking may often be used in lieu of noncombustible construction in open warehouses, storage sheds, and structures with no penalty in the insurance rates or the building code classification of the structure.

ExteriorFireX 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.

FRTW Education

Tap into continuing education from the industry leader.

Quick, convenient courses, certified by the American Institute of Architects (AIA) for HSW/AXP credit and delivered by International Code Council (ICC) Preferred Education Providers.

Code Acceptability

Each piece of ExteriorFireX fire-retardant-treated lumber and plywood bears the UL Solutions label as required by building codes.

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

-Military Specification MIL-L-19140E

-International Code Conference (ICC)

-Wildland Urban Interface (WUI)

-Insurance Service Office (ISO)

-American Nuclear Insurers

-Nuclear Mutual Limited


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

Wood Siding

ExteriorFireX fire-retardant-treated wood siding combines the economy and natural beauty of wood siding with the insurance and safety advantages of fire-retardant-treated wood siding.

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

ExteriorFireX fire-retardant-treated wood siding is often accepted as an alternative for noncombustible siding.

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

ExteriorFireX Blue

ExteriorFireX Blue is color coded with a pressure-applied blue stain for easy identification. It has the same fire performance characteristics, ratings, and approvals as ExteriorFireX. ExteriorFireX is widely specified by government agencies and is used in the nuclear construction and ship-building industries.