Pyro-Guard is pressure-impregnated, interior fire-retardant treated lumber and plywood for enclosed structural applications.


Pyro-Guard is recommended for enclosed structural applications such as:

  • Plywood roof sheathing
  • Roof trusses
  • Rafters
  • Floor joists
  • Mezzanines
  • Shelving
  • Load-bearing walls
  • Floor sheathing
  • Partition walls
  • Studs
  • Interior beams
  • Blocking
  • Steps
  • Stairways
  • Platforms
  • Stages
  • Plywood subfloors
  • Wall sheathing
  • Telecomm/electrical panels

Pyro-Guard has been strength-tested after prolonged exposure to elevated temperatures and moisture to verify its strength characteristics when used in roof systems and other recommended applications.

Pyro-Guard plywood span ratings and lumber design value adjustments are based on strength testing after prolonged exposure to high temperatures experienced in roof applications.

Pyro-Guard fire-retardant treated wood is produced in strategically located company-owned facilities and is distributed by an extensive nationwide network of stocking distributors.

Exterior Fire-X® retardant treated wood is recommended for exterior exposures and other applications exposed to dampness, high humidity or wetting.

E-mail Hoover’s Technical Service Department or request sales information.

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  • Construction with Pyro-Guard treated wood requires no special tools or skills.
  • Pyro-Guard trusses and roof decks often qualify a masonry wall building as “non-combustible” for insurance purposes.
  • Pyro-Guard can often be substituted for non-combustible materials without affecting building classification.
  • Use of Pyro-Guard wood partitions instead of untreated partitions often allows for an increase in square footage and lower insurance rates.
  • The use of Pyro-Guard wood roof decking is usually accepted in lieu of parapet walls in multi-family dwellings.
  • Even when sprinklers are mandatory, the use of Pyro-Guard can further reduce fire insurance rates.
  • Pyro-Guard is commonly accepted by building codes for partition walls, store fronts, fixtures and roof construction in shopping centers.

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Fire Performance

Pyro-Guard is pressure impregnated deep into the wood to provide permanent protection, unlike coatings, which only provide superficial protection.

When Pyro-Guard treated wood is exposed to fire, non-combustible gas and water vapor are produced, and a layer of protective char forms, which hinders combustion and insulates the wood against further damage.

Pyro-Guard interior fire-retardant treated wood has a low rate of fuel contribution and heat release, and it maintains structural integrity longer than other building materials such as steel. Consequently, fire damages and repair costs are minimized, resulting in reduced insurance rates.

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Smoke Toxicity

Pyro-Guard has successfully passed a stringent combustion toxicity test. Smoke produced by Pyro-Guard treated wood was no more toxic than smoke produced by untreated wood.

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Code Compliance

Pyro-Guard was the first FRTW (fire-retardant treated wood) to be issued a Code Compliance Report based on high temperature testing for roof sheathing and framing uses.

UL Evaluation Report ER7002-01 has been issued for Pyro-Guard by Underwriters Laboratory, confirming compliance with the International Building Code.

UL Evaluation Report ER7002-01 contains conditions of use and strength adjustments for roof sheathing, roof framing and other applications.

Pyro-Guard 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.

Pyro-Guard is often approved as a substitute for non-combustible materials in applications such as wall studs and roof systems.

Pyro-Guard should not be confused with fire-retardant surface coatings, because test requirements and code definitions are entirely different for each. Pyro-Guard is pressure impregnated and carries a flamespread rating derived by Underwriters Laboratories in the 30 minute ASTM E-84 flamespread test, while coatings are sprayed, brushed or rolled on the surface and flame 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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Hoover Treated Wood Products, Inc. warrants PYRO-GUARD ® fire retardant treated wood against defects in manufacture where the product is properly installed up to a maximum of 20 years. This warranty entitles the holder to repair or replacement of defective material, including the reasonable cost of labor and materials.

Hoover Treated Wood Products, Inc. warrants that its’ PYRO-GUARD ® interior fire retardant treated wood is manufactured under Underwriters Laboratories independent third-party Follow Up Inspection Service and that it meets or exceeds the following code requirements for interior fire-retardant-treated wood:

  • International Building Code
  • International Residential Code
  • Military Specification MIL-L-19140

Further, PYRO-GUARD ® treated wood products will meet or exceed the relevant ASTM Standards (E-84, D-3201) for interior fire retardant treated lumber and plywood.

PYRO-GUARD ® fire treated wood can only be used for interior applications involving dry conditions of use above grade and not exposed to weather, dampness or wetting. It shall be stored, protected, applied and used during construction in accordance with Hoover Treated Wood Products, Inc.’s specifications and recommendations. Use of PYRO-GUARD ® fire retardant treated wood as roof sheathing without proper ventilation for moisture control invalidates the terms of this warranty. No other warranty, expressed or implied, including warranties of merchantability or fitness, shall apply.

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The natural wood color and texture remains intact with Pyro-Guard. Raised grain may occur, especially on sanded plywood, and this is easily removed by sanding. Stick marks may be minimized by special order.

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Engineering Calculations with Pyro-Guard

Pyro-Guard was the first FRTW with plywood roof span ratings and lumber strength adjustments based on strength testing after prolonged exposure to elevated temperatures and moisture.

Furthermore, Pyro-Guard was the first FRTW to be issued a Code Compliance Report which includes evaluation of elevated temperature strength testing.

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Pyro-Guard was the first interior fire-retardant treatment with plywood roof span ratings and lumber strength adjustments based on high temperature testing. Plywood was strength-tested after exposure to 170 degrees F, and lumber was strength-tested after exposure to 150 degrees F according to ASTM 5516 and ASTM 5664. As a result, Pyro-Guard can be used with confidence in all recommended structural applications, including plywood roof sheathing and roof trusses.

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Finishing Pyro-Guard Fire Retardant Treated Wood

Pyro-Guard interior fire-retardant treated wood can be finished or painted. As with untreated wood, the wood must be dry and clean before finishing.

Pyro-Guard fire retardant treated wood, like any other type of wood, should only be finished after the structure is enclosed and mechanical equipment is placed in service. This allows the moisture content in the wood to stabilize at an acceptable level.

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

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Ventilation, Moisture and Heat

Adequate air flow must be provided in wood roof systems to prevent moisture buildup in the wood. It is the sole responsibility of the building owner or his agent (builder, architect, engineer, etc.) to insure that ventilation meets or excedes the building code requirements.

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Job Site Storage

As with untreated wood, it is important to keep Pyro-Guard material dry by covering the top of the bundle, storing the material under shelter, elevating the bundle from ground contact, and allowing for air circulation around the wood. Roof sheathing should be covered as soon as practical after installation. If wetted during construction, allow to dry before enclosure or covering with roofing material.

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Hygroscopicity and Corrosiveness

The hygroscopicity (moisture absorbency per ASTM 3201) and corrosiveness of Pyro-Guard fire-retardant treated wood is far lower than the maximum allowed by industry and governmental standards. Even though testing indicates that carbon steel fasteners can be compatible with Pyro-Guard, galvanized fasteners are recommended.

Pyro-Guard is safe to use with galvanized truss plates, duct work, plumbing, conduit and copper. It contains no halides, sulfates or ammonium phosphates.

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Third-Party Monitoring of Kiln Drying After Treatment

All building codes require fire-retardant treated wood to be dried after treatment. Kiln drying restores stiffness and strength, increases dimensional stability and reduces shipping weight.

Kiln drying of Pyro-Guard is monitored by Timber Products Inspection Inc. to assure conformance to Production Standard 2200. This unique standard was developed by Hoover to assure that treating and re-drying methods are consistent with those used to produce materials tested for long-term strength properties. This monitoring program is in addition to UL Follow-Up Service which assures fire performance.

Such quality control is possible because Pyro-Guard is produced in company-owned treating plants and by a select group of licensees, allowing complete control of all facets of production.

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Pyro-Guard is recommended for enclosed interior applications not exposed to the weather, dampness, high humidity or wetting. When codes require exterior fire retardant treated wood Exterior Fire-X is available.

Pyro-Guard is allowed for use in contact with concrete or masonry that is above grade and is not susceptible to wetting or dampness.


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