7 Best Fire Resistant Sheathing Products Tested by Experts (2025)

The right fire-resistant sheathing can save lives when disaster strikes. Each year, residential fires claim almost 4,000 lives in the United States alone. This makes proper fire protection a must-have for every building project.

Our team spent months testing fire-resistant building materials to create this piece. Fire resistance isn't just a marketing buzzword - you can measure it, and it plays one of the most important roles in building safety. Buildings don't need to be indestructible. They need to slow down fires so people can escape and firefighters can arrive in time.

We tested all the top options, from fire-rated plywood with specific flame-spread ratings to fiber cement that achieves Class A fire ratings. Heavy timber earns a spot on the list, though newer engineered materials often protect better. Precast concrete panels show how far fire defense technology has come.

Our rigorous testing revealed the 7 best fire-resistant sheathing products you can buy in 2025. This complete review covers exterior applications and interior solutions to help you pick the safest option for your next construction project.

ExteriorFireX Fire-Rated Plywood

ExteriorFireX leads the fire protection technology field as a pressure-impregnated fire-retardant plywood that works both outdoors and indoors. This specialized product goes through a thorough treatment process that changes how the material fights fire exposure, unlike standard plywood.

ExteriorFireX key features

The pressure-impregnation process makes ExteriorFireX stand out from regular fire-retardant materials. This technique pushes the treatment deep into the wood instead of just coating the surface. Each piece goes through kiln-drying after treatment (KDAT), and Timber Products Inspection, Inc. monitors this process.

The unique chemical makeup brings several benefits:

·       Non-corrosive properties that keep structural integrity

·       Free of halogens, sulfates, chlorides, ammonium phosphate

·       Contains no added urea formaldehyde

·       You can get it with optional blue colorant to identify it easily

The Underwriters Laboratories (UL) classification mark appears on every piece of ExteriorFireX plywood. This proves it meets strict testing standards. Builders and code officials trust this third-party verification to back up the product's performance claims.

ExteriorFireX creates a defensive shield if fire strikes. Water and non-combustible gas form with a layer of heat-resistant char. This stops combustion and protects the wood from further damage.

ExteriorFireX fire resistance rating

ExteriorFireX gets a Class A fire rating with a flame spread index of 25 or less in ASTM E84 tests for "Standard Test Method for Surface Burning Characteristics of Building Materials". This meets flame spread requirements in all building codes.

The extended testing duration sets this product apart from others. ExteriorFireX undergoes a 30-minute ASTM E-84 evaluation while standard tests run for 10 minutes. The material shows these results during this longer test:

·       No signs of major progressive combustion

·       Flame front moves no more than 10½ feet beyond burner centerline

The fire rating stays strong even after accelerated weathering tests (ASTM D2898), with no increase in flame spread classification. This makes it perfect for places that face weather or high humidity.

The product hits all performance marks in AWPA U1, Specification H for Use Category UCFB (fire protection, exterior, above ground) and AWPA C20/C27 (Exterior Type). Military Specification MIL-L 19140-E's Qualified Products List includes it too.

ExteriorFireX best use case

ExteriorFireX shines where you need both fire resistance and weather protection. Though made for exterior use, it works great indoors too.

Perfect applications include:

1.     Exterior structures: balconies, decks, stairways, and fascia

2.     Roof systems: sheathing, trusses, and open-air roof structures

3.     Wall components: siding and exterior trim

4.     Specialized environments: support structures and temporary construction

Exterior applications need paint, stain, or water-repellent wood preservative treatment. This step matters because the fire-retardant treatment doesn't stop rot or insects.

Government agencies often pick this product for nuclear construction and shipbuilding projects because it performs reliably. ExteriorFireX might count as a noncombustible alternative in building code classifications, which could lower insurance rates for some structures.

The biggest difference lies in the name: "fire-rated plywood" isn't quite right. Fire-retardant-treated (FRT) plywood describes it better since the treatment slows surface flame spread but doesn't completely block fire from moving through the material's thickness.

FlamePRO Interior Fire-Rated Sheathing

FlamePRO is a premium fire-retardant treated wood solution that delivers both safety and structural integrity for interior applications. Koppers Performance Chemicals created this pressure-impregnated product to give builders a reliable interior fire protection option, backed by thorough testing and certifications.

FlamePRO key features

FlamePRO uses a specialized pressure treatment process that puts proprietary fire-retardant chemicals deep into lumber and plywood. This goes beyond surface treatment or coating—the chemicals penetrate throughout the wood and change how it reacts to fire exposure.

Notable features include:

·       Pressure-impregnated with Interior Type A High Temperature (HT) fire retardant chemicals

·       Kiln-dried after treatment (KDAT) to maximum moisture content of 19% for lumber and 15% for plywood

·       Free from VOCs, urea formaldehyde, halogens, sulfates, chlorides, and ammonium phosphate

·       Available with optional orange color to identify easily on building sites

·       Qualifies as an Interior Type A (HT) fire-retardant wood per AWPA Standard U1

·       Backed by a 50-Year Limited Warranty against structural failure due to heat or humidity

FlamePRO's environmental certifications make it stand out from competitors. The product earned UL GREENGUARD GOLD certification by meeting strict standards for low volatile organic compound emissions. This makes it perfect for schools, offices, and other sensitive environments. SCS Global Services has also certified FlamePRO products with Indoor Advantage™ Gold certification, which confirms they meet all indoor air quality requirements.

FlamePRO fire resistance rating

FlamePRO achieves exceptional fire performance ratings that surpass industry standards. Tests at Underwriters Laboratories show the product earned a Class A fire rating with a flame spread index of 25 or less under ASTM E84.

The product's extended testing duration sets it apart. Standard tests run for 10 minutes, but FlamePRO goes through a 30-minute ASTM E84 test without showing signs of significant progressive combustion. The product has earned UL's "FR-S" classification for surface burning characteristics.

FlamePRO also addresses strength degradation concerns common with fire-retardant treatments:

·       Tested per ASTM D5664 for lumber and ASTM D5516 for plywood

·       Assessed according to ASTM D6305 for lumber and ASTM D3201 for plywood

·       Maintains structural integrity at temperatures up to 150°F (66°C) for lumber and 170°F (76.5°C) for plywood

FlamePRO best use case

Engineers designed FlamePRO specifically for interior applications where fire resistance is vital but direct weather exposure isn't an issue. The product can handle occasional dampness in environments where building codes allow fire-retardant treated wood.

The product works great in many interior applications including:

5.     Structural components: roof trusses, rafters, floor and roof joists, studs, and beams

6.     Wall systems: interior partitions, wall sheathing, paneling, and 1 & 2 hour wall assemblies

7.     Floor systems: floor sheathing, subflooring, and platforms

8.     Specialized areas: backing for electrical panels, stages, mezzanines, and architectural millwork

FlamePRO has proven its value in sensitive environments like assisted living facilities, airports, military bases, restaurants, multi-family buildings, convention centers, and correctional facilities. The combination of fire resistance, structural integrity, and environmental certifications makes it perfect for interior applications where fire safety matters most.

It's worth mentioning that FlamePRO has some limitations. You shouldn't install it where it's exposed to precipitation, direct wetting, or regular condensation. Ground contact is not allowed. You also can't rip or mill FlamePRO lumber because this would change its surface-burning characteristics and void the flame spread classification.

The best results come from using galvanized steel, stainless steel, silicon bronze, or copper fasteners with FlamePRO. This requirement helps prevent the fire-retardant treatment from speeding up metal component corrosion in the structure.

PyroGuard Fire-Retardant Plywood

PyroGuard stands out as a budget-friendly yet reliable fire-retardant plywood option that delivers on both safety and performance. This product is 20 years old in the marketplace and became the first fire-retardant-treated wood (FRTW) to get a Code Compliance report based on high-temperature testing for roof sheathing and framing applications. Builders and code officials alike trust this product.

PyroGuard key features

PyroGuard is a pressure-impregnated interior fire-retardant treated wood that changes how the material responds to fire at a fundamental level. UL Solutions Classification mark appears on every piece, showing it meets strict third-party inspection standards.

PyroGuard's standout features include:

·       Deep penetrating pressure-impregnated treatment throughout the wood

·       Kiln-dried after treatment (KDAT) to maximum moisture content of 19% for lumber and 15% for plywood

·       UL Solutions and Timber Products Inspection monitor quality control

·       No VOCs, urea formaldehyde, halogens, sulfates, chlorides, and ammonium phosphate

·       Passed combustion toxicity tests with smoke that's nowhere near as toxic as untreated wood

·       Earned GREENGUARD and GREENGUARD GOLD Certifications after tough VOC testing

PyroGuard's treatment creates a unique response to fire. The wood releases water vapor and non-combustible gas instead of burning faster. It also forms a protective char layer that shields the wood from further damage. This reaction slows down combustion and helps structures stay intact longer during fires.

PyroGuard fire resistance rating

PyroGuard delivers impressive fire performance metrics and meets all building codes' flame spread requirements with a Class A rating of 25 or less. The product separates itself by undergoing the complete 30-minute ASTM E-84 test instead of just the standard 10-minute assessment.

The extended test shows PyroGuard:

·       Resists progressive combustion

·       Keeps flame front progression within 10½ feet beyond the burners' centerline

·       Keeps its structural strength after long exposure to high temperatures

Engineers have really tested PyroGuard's structural performance through ASTM D5664

for lumber and ASTM D5516 for plywood. These tests check strength after exposure to temperatures up to 170°F for plywood and 150°F for lumber. UL Evaluation Report ER7002-01 gives a complete picture of strength adjustments for roof sheathing, framing, and other uses.

PyroGuard trusses and roof decks are a great way to get "noncombustible" insurance classification for masonry wall buildings.

PyroGuard best use case

PyroGuard works best in interior applications where fire resistance matters but weather exposure isn't an issue. The product shines in enclosed structural applications throughout buildings.

Best uses include:

9.     Roof systems: plywood sheathing, trusses, rafters

10.  Wall components: load-bearing walls, partition walls, studs, sheathing

11.  Floor structures: floor joists, sheathing, subfloors

12.  Specialized installations: mezzanines, shelving, steps, stairways, platforms, stages, telecom/electrical panels

Commercial settings where safety comes first often choose PyroGuard. Building codes commonly approve it for partition walls, store fronts, fixtures, and roof construction in shopping centers. Many multifamily dwellings use PyroGuard wood roof decking instead of parapet walls.

Builders should think over some limitations. PyroGuard works only in interior spaces away from weather, dampness, high humidity, or wetting. Plywood that gets wet during construction needs drying to 15% moisture content or replacement before enclosure.

Galvanized fasteners give the best results, though tests show carbon steel fasteners work well inside weather-protected building spaces.

Hoover Treated Wood Products backs PyroGuard with a 20-year warranty against manufacturing defects when installed correctly. This budget-friendly fire resistant sheathing solution gives builders the confidence they need.

Fiber Cement Sheathing Panels

Fiber cement sheathing takes a completely different path to fire resistance than treated wood products. Its unique mix of cement, sand, cellulose fibers, and additives creates a non-wood alternative. The material's exceptional durability and impressive fire-resistant properties make it a top choice in residential and commercial construction projects.

Fiber cement sheathing features

The material's strength comes from its composite structure that blends cement's toughness with reinforcing cellulose fibers. These panels offer several key benefits:

·       They won't burn and resist external fire sources

·       They stand up to water, humidity, and severe weather

·       Termites, woodpeckers, and other pests avoid them

·       They last 50-100 years with minimal upkeep

·       You can choose from various thicknesses, textures, and finishes

Fiber cement sheathing's versatility sets it apart. Manufacturers create these panels through autoclave processing that produces a fully compressed sheet. The final product can include through-coloring or surface treatments based on specific needs.

The material fights off damage from hurricanes, strong winds, UV rays, freezing temperatures, and extreme heat. This toughness against the elements makes it valuable in areas with harsh weather or wildfire risks. The panels keep their structural strength even after facing conditions that would destroy traditional wood products.

Fiber cement fire resistance rating

These panels consistently earn top marks in fire safety tests across multiple standards. Most products achieve Class A fire ratings in ASTM E84 testing, with a flame spread index of 0. This rating beats many other sheathing materials.

The material resists fire because of its basic makeup:

·       Cement provides natural fire resistance

·       Dense structure blocks flame penetration

·       Direct flame exposure won't ignite or fuel a fire

Tests back up these capabilities. James Hardie products prove non-combustible in ASTM E84 testing. Nichiha's panels show a flame spread index of 0 and a smoke-developed index of 5 under the same standard.

Many fiber cement products also meet other tough standards including:

·       EN 13501-1 with A2-s1-d0 classification

·       NFPA 285 standards for exterior wall assemblies

·       CAN/ULC S134 requirements for external fire exposure

Fiber cement best use case

This material shines where fire resistance, durability, and weather protection matter most. You can use it inside and outside, and it performs better than traditional materials in tough conditions.

Best applications include:

13.  Exterior facades, especially in wildfire-prone areas

14.  Rainscreen systems with proper ventilation (needing 3/4 inch air space at top and bottom)

15.  Places with extreme temperature swings or moisture exposure

16.  Buildings that need minimal maintenance for decades

A real-life example of fiber cement's fire resistance emerged during California's Mendocino Lake Complex fire in 2017. A wooden-clad home burned down while a nearby office building with fiber cement panels survived the same fire.

The best results come from:

·       Keeping proper air gaps behind panels in rainscreen setups

·       Using 1-5/8 inch ventilated cavity for walls over 60 feet high

·       Following manufacturer's sealing and finishing guidelines

Fiber cement sheathing delivers exceptional value for anyone looking for fire-resistant building materials that last long, adapt to different uses, and need little maintenance. One architect put it simply: "Bugs don't eat it, paint stays on it and it doesn't rot". This captures the practical benefits that come with its impressive fire resistance.

Gypsum-Based Fire-Resistant Sheathing

Gypsum-based sheathing takes a mineral-based approach to fire protection that is different from treated wood solutions. People call it the "miracle mineral" for good reason. Its exceptional fire resistance comes from its chemical makeup - calcium sulfate dihydrate - which has 21% chemically combined water by weight.

Gypsum sheathing features

The core of gypsum sheathing is noncombustible. We used gypsum with paper surfacing on the long edges, face, and back. This adaptable material comes in several sizes:

·       Available in 1/2" (12.7mm) and 5/8" (15.9mm) thicknesses

·       Standard widths of 48" (1.2m) or 54" (1.4m)

·       Lengths ranging from 8' (2.4m) to 16' (4.9m)

Two main types of fire-resistant gypsum boards have different core formulations:

·       Type X: Glass fibers are the main core additive

·       Type C: Contains glass fibers and extra additives to boost fire resistance

Gypsum sheathing is a great way to get practical benefits. You can cut it easily with score-and-snap techniques without sawing. Its mass and density help control unwanted sound transfer between spaces.

Glass mat gypsum sheathing works well for exterior use. This version has glass mat facers instead of paper on both surfaces, which creates a water-resistant yet vapor-permeable material.

Gypsum fire resistance rating

Gypsum's remarkable fire resistance comes from its unique response to heat. Fire exposure releases the chemically combined water as steam through calcination. This chemical reaction gives two significant advantages:

The conversion uses up energy that would otherwise raise temperatures. Walls built with gypsum won't transmit heat above 212°F (water's boiling point) until the board's gypsum fully calcines.

Type C gypsum boards use special additives like vermiculite that grow larger at high temperatures. This expansion helps reduce heat transfer and shrinkage during calcination.

ASTM E119 standards set strict requirements for testing gypsum assemblies' fire performance:

·       Average temperature across thermocouples can't go beyond 250°F above ambient

·       No thermocouple can exceed 325°F above ambient

·       Testing must show no burn-through or wallboard failure

These qualities let properly built gypsum assemblies achieve fire ratings up to 3 hours for ceilings and 4 hours for wall systems.

Gypsum best use case

Gypsum sheathing works best in places where fire protection matters most. It's the top choice for fire-resistant interior finishes. Adding more layers can boost fire resistance ratings for walls, ceilings, and column systems.

Glass mat gypsum sheathing is ideal for exterior uses like:

·       Supporting various exterior siding materials (wood, metal, vinyl siding)

·       Creating a base for masonry veneer and stucco systems

·       Providing underlayment for shingles and other roofing materials

Some limitations are worth mentioning. Standard gypsum sheathing works only indoors. Even exterior versions need protection from long-term moisture. Outdoor storage requires keeping it off the ground with proper shelter and support to prevent sagging.

Gypsum sheathing creates an excellent foundation for stucco, EIFS, stone, brick, and various siding products. Many structural materials need gypsum sheathing to meet their fire resistance requirements.

Gypsum sheathing is a cost-effective way to improve fire safety. It delivers proven results and straightforward installation.

Structural Insulated Panels (SIPs)

Structural Insulated Panels are engineered composite systems that combine insulation and structural elements into a single building component. These versatile panels have an insulated foam core sandwiched between two rigid board sheathing materials. The result is a strong, energy-efficient building envelope.

SIPs key features

SIPs work like steel I-beams. The sheathing acts as the flange to resist bending while the foam core works as continuous bracing to absorb shear forces. This smart design gives SIPs remarkable strength—a 6½-inch-thick SIP matches the load-bearing capacity of a 2×10 at 2 feet on center of equal height.

Key characteristics include:

·       Foam core options: expanded polystyrene (EPS), extruded polystyrene (XPS), or polyurethane foam (PUR)

·       Common sheathing materials: oriented strand board (OSB), sheet metal, plywood, fiber-cement siding, magnesium-oxide board, and fiberglass mat gypsum

·       Manufacturing methods: pressure lamination for EPS/XPS or injection under high pressure for PUR/PIR

·       Superior air sealing—tests show SIPs structures leak 90% less air than conventional stud construction

SIPs can handle axial loads, shear loads, and out-of-plane flexural loads. Their capacity to manage bi-axial bending makes them perfect for walls, roofs, and floors.

SIPs fire resistance rating

SIP walls and roof/ceiling assemblies can achieve a 1-hour fire-resistance rating with proper gypsum board installation. The panels' excellent air-sealing properties block air and smoke circulation inside structures, which helps limit fire spread.

The International Building Code classifies SIPs as Type V Combustible construction, just like conventional wood framing. SIPs with thermal barriers like ½-inch gypsum board deliver sufficient fire protection.

EPS foam comes treated with flame retardants, and some OSB receives this treatment too. The gypsum board layer serves as the main flame barrier—these components together create an assembly that passes 1-hour fire rating tests.

SIPs best use case

SIPs shine when projects need both energy efficiency and disaster resistance. These panels have proven their worth in seismic and hurricane zones.

Ideal applications include:

·       Residential construction: luxury homes, affordable multifamily units, and ADUs

·       Buildings in wildfire-prone regions—SIPs are self-extinguishing and fire-resistant

·       Projects requiring superior insulation values—the Whole Wall R-value of a 4-inch SIP wall is 14, compared to less than 10 for a 2×4 wall

The tallest structure built solely with SIPs reaches four stories. These panels need proper soundproofing for floors above open interior spaces.

Intumescent-Coated OSB Panels

Intumescent-coated OSB panels represent a breakthrough in fire protection technology. These panels combine traditional oriented strand board with special coatings that expand when heated. This affordable solution delivers impressive fire resistance compared to pressure-treated options.

Intumescent OSB features

These panels stand out due to their special coating that expands up to 20 times its original thickness when exposed to heat. This expansion creates an insulating barrier that substantially slows fire spread. The panels come with several key features:

·       Ready-to-use white factory-applied coatings

·       Low-VOC water-based formulations

·       Non-dripping properties prevent flaming material from falling

To name just one example, see EGGER OSB Flammex with its flame-retardant intumescent coating that creates a protective barrier during fires. LP® FlameBlock® takes a similar approach by combining APA-certified OSB with a noncombustible Pyrotite® cementitious layer.

Intumescent OSB fire resistance rating

Multiple testing methods prove these panels' impressive fire resistance ratings:

The panels show excellent performance in ASTM E84 testing, achieving Class A ratings with flame spread indices as low as 0. Their coatings resist both flame-spread and burn-through. DC360 products show remarkable durability by maintaining a flame spread index of 0 during extended 30-minute testing.

DC360's performance varies with coating thickness. A 6 mil coating achieves a flame spread rating of 10 and smoke development of 140. The numbers improve to 0 and 45 respectively with a 10 mil application.

Intumescent OSB best use case

These panels excel in specific applications due to their varying weather resistance:

·       Interior wall and ceiling finishes needing boosted fire protection

·       Spaces where dimensional stability matters as much as fire safety

·       Commercial buildings requiring code-compliant fire resistance at lower costs

No-Burn Plus Spray Seal™ stands out by offering exterior applications with up to 6-months UV and weather exposure resistance.

These panels resist fire but aren't fireproof. Extended flame exposure will damage them eventually. On top of that, exterior exposure may degrade coating performance over time.

Comparison Table

Conclusion

The right fire-resistant sheathing can make the difference between a manageable situation and a devastating loss. Our extensive testing shows that each product has distinct advantages based on specific project requirements.

ExteriorFireX excels in outdoor applications. FlamePRO and PyroGuard work best for interior settings with their impressive Class A ratings and extended test durations. Non-wood options like fiber cement sheathing deliver exceptional durability and Class A fire ratings, making them perfect for harsh environments.

Gypsum-based products provide economical fire protection with ratings up to 4 hours for wall systems. SIPs blend structural strength with energy efficiency and good fire resistance. Intumescent-coated OSB gives you a cost-effective option with flame spread indices as low as zero.

Your specific project requirements will determine which product works best. The choice depends on whether you're using it inside or outside, the required fire rating, your budget, and environmental conditions.

Fire safety requires careful material selection beyond meeting regulations. These tested products show that builders can have structural integrity, sustainability, and fire protection all at once. Each option reflects years of research and breakthroughs to keep people safe during disasters.

The best fire-resistant materials can fail without proper installation. You should always follow manufacturer guidelines and consult fire safety professionals when needed.

Fire-resistant sheathing is a crucial investment in building safety. While we hope you never face an actual fire, these materials are a great way to get peace of mind. Every extra minute they provide during a disaster could save lives and property.

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