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Frequently Asked Questions

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What is FlameBlock?

LP FlameBlock^® is a structural, fire-rated panel used in both new construction and renovation projects. The panel’s fire-resistive properties are provided by Pyrotite® technology – a patented process that provides a non-hazardous, cementicious coating bonded to oriented strand board. Pyrotite is non-combustible and when exposed to the heat of fire will release molecularly bound water. The water cools the panel’s surface and slows the spread of fire.

Is the FlameBlock product based on proven technology?

Yes. LP FlameBlock is manufactured with proven Pyrotite technology that has been used to produce structural fire rated sheathing in the US since 1991.

Where are FlameBlock panels used?

LP FlameBlock is most commonly used as:

a structural roof sheathing in multifamily roof decks along fire walls
a component of interior or exterior fire-rated structural wall assemblies
an ignition-resistant open soffit panel (installed coated side down on roof deck and left exposed in eave)
a roof deck panel in both Class A and C low-slope commercial roof deck assemblies
a thermal barrier for foam core panels, including structurally insulated panels (SIPs)

The product is specified by architects or engineers, and its code-compliant applications are outlined in ICC ESR-1365 .

What is the fire rating of FlameBlock?

LP FlameBlock is rated for flame spread and smoke development as well as burn-through resistance. LP FlameBlock is a Class A (or I) flame and smoke rated panel as determined by the ASTM E-84 (UL 723) Flame Spread test conducted by Underwriters Laboratories. LP FlameBlock meets Class A commercial low slope roof deck assembly requirements under single-ply membranes, exceeds the 15-min. thermal barrier requirement for foam core plastics, and is listed in a variety of 1 and 2-hr load bearing wall assemblies.

Does the coating side face in or out?

The orientation of the coated face of the panel depends on the application. Please review the Application Instructions that pertains to your particular use. In general, the coated side is oriented to face the side of the roof or wall where protection from fire is required.

I like the finish on FlameBlock — can I use it for interior purposes with the surface exposed?

The OSB substrate in FlameBlock will expand and contract slightly with changes in humidity. Therefore, joints between panels should be gapped 1/8-inch. The Pyrotite surface of standard FlameBlock panels is stamped to show certifications of fire and structural performance. The panel faces may exhibit variation in color and texture. LP FlameBlock may be painted with a good quality interior or exterior paint to achieve a more finished appearance.

Is it available with the Pyrotite coating on both sides?

Yes, LP FlameBlock is available with the Pyrotite layer on either one or both sides, depending on the application.

What if the Pyrotite coating is damaged during installation?

The adhesion, resiliency, and fiberglass reinforcement of the Pyrotite coating makes it very resistant to impact and tear-out. If, however, small pieces are removed during installation, the affected area can be easily repaired with standard drywall joint compound. For larger repairs, Pyrotite laminate can be quickly shipped to a job site and mechanically fastened to a panel with nails or staples, in accordance ICC code report ESR1365.

How do I treat the panel edges?

LP FlameBlock was tested with the edges untreated. Building codes require that field applications mimic laboratory conditions so no further treatment of the panel edges is required. Standard panel spacing practices should be observed. Always check the relevant Application Instructions to be sure installation in the field is done correctly.

What about roofing nails protruding the surface of the coating?

Protruding roofing nails were shown in fire tests NOT to reduce the fire rating of the panel.

What is the panel strength?

The fiberglass-reinforced Pyrotite coating strengthens the panel. The span and load ratings meet or exceed those of fire rated plywood or OSB panels in the same performance category, as verified by independent , ISO-certified testing laboratory Progressive Engineering Inc. (PEI). Each panel is individually labeled with a span rating. Load/span and shear rating tables are here.

Is FlameBlock available in Structural Rated Panels?

Yes, LP FlameBlock is available in Struc-1 rated panels of varying performance categories and lengths.

Who tests and certifies FlameBlock?

LP FlameBlock has an International Code Council (ICC) Evaluation Services (ES) report, ESR-1365 , which lists the code compliant applications. In addition, LP FlameBlock is listed and subject to quarterly quality control inspections with two independent laboratories: Intertek (Omega Point Laboratories) and Underwriters Laboratories (UL). LP FlameBlock is also included as an approved product on the California State Fire Marshall’s Wildland Urban Interface List (WUI) for exterior wall sheathing, under eave applications, and ignition resistant building materials. It is also approved for use in the City of Los Angeles (LARR #25875 ).

What are the key FlameBlock advantages?

LP FlameBlock’s key advantage is that the panel combines fire resistance and structural performance in a single panel. In the right applications, LP FlameBlock can reduce the time and cost associated with having to install either double-layers of gypsum, or a combination of gypsum and structural sheathing. Using a single panel reduces the wall thickness, saving the cost of configuring window and door frames to accommodate thicker walls. FlameBlock’s Exposure 1 certification means that it is bonded with water-resistant adhesives and withstands exposure to moisture during normal construction delays.

What are the dimensions of FlameBlock panels?

LP FlameBlock panels can be made in all standard OSB performance categories in 4’ x 8’, 4’x9’ and 4’x10’ lengths. LP OSB Sheathing panels are sized to 3’ 11-7/8” x 7’ 11-7/8” dimensions (reduced 1/8” from 4’ x 8’ to allow for proper spacing during installation). Panels are available in performance categories ranging from 15/32-inch to 1-1/8. Extended length and oversized panels are subject to availability.

What are performance categories?

Performance category replaces the fractional nominal thickness used in U.S. Voluntary Product Standard PS2. The Performance Category is consistent with the panel thickness used in the U.S. model building codes.

How much do FlameBlock panels weigh?

The Pyrotite coating itself adds approximately .7 lbs per square foot to a board. Thus, a 4’ x 8’, 15/32 Category LP FlameBlock panel coated on one side weighs approximately 66 pounds, and about 85 pounds with the coating on both sides. As a comparison, the combined weight of a layer of a 4’ x 8’ 5/8” gypsum board plus a 4’ x 8’ 15/32 sheathing panel can easily be 120 pounds.

How do you install FlameBlock panels?

Installation is similar to standard sheathing. LP FlameBlock can be cut and installed with standard carpentry tools. LP FlameBlock has been shown in relevant testing not to corrode nails, so standard nails, screws, and fastening patterns may be used. Carbide-tipped saw blades are recommended. Blades may have to be sharpened or replaced about 20% more often than if cutting standard panels only.

Is the dust from cutting FlameBlock dangerous?

Third party testing has show that silica and dust exposure levels during product usage were below the OSHA Permissible Exposure Limits (PELs.) As when cutting any wood product, a proper fitting dust mask and eye protection with side shields should be worn. CALIFORNIA PROP 65 WARNING: Use of this product may result in exposure to wood dust, known to the state of California to cause cancer.

Can I cover FlameBlock with any type of siding?

Fire-rated, exterior wall assemblies often specify the exterior claddings for which the assembly’s rating is valid. In addition, local code officials have jurisdiction over what types of sidings and coverings can be attached to fire-rated walls and roofs, and should be consulted for information on the approved siding options in a given municipality.
Does FlameBlock reduce sound transmission?
Testing is currently underway to provide sound transmission coefficients for wall assemblies utilizing LP FlameBlock.
Where can I buy FlameBlock?
LP FlameBlock will be distributed by most building material suppliers that carry other LP branded products. Please contact your LP representative to locate a dealer near you.

What does FlameBlock cost?

LP FlameBlock panel costs vary based on panel size, dimension, geography and volume. LP FlameBlock is priced competitively to other alternatives. In addition, using LP FlameBlock will save the builder time and money overall, as well as provide the best performing and safest fire-resistant sheathing technology available. For pricing on any specific order of LP FlameBlock, please contact your LP representative or email us.

Has FlameBlock or Pyrotite^® technology ever experienced any issues associated with their use?

The use of Pyrotite technology as a coating for structural wood based panels has been very successful. As with any roof deck material it is important that the attic space below the panel be ventilated at least to building code standards. The build-up of humidity in a poorly ventilated attic space, coupled with temperature fluctuations in northern environments, may cause condensation to form on the surface of structural panels, including LP FlameBlock.

Where has LP FlameBlock been used?

LP FlameBlock is currently in use in different applications across the US. Please check the case study section of our website or contact your local LP representative for specific examples.

Where can I find code-compliant wall assemblies for LP FlameBlock?

A number of wall assemblies are available, and can be accessed here. More wall assemblies are under development.

What is the warranty for LP FlameBlock?

LP FlameBlock carries a twenty-year transferrable limited warranty that covers fire rating at time of manufacture as well as delamination. For full details, please read the warranty available here.

Frequently Asked Questions

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