Meeting Fire Code Requirements Without Sacrificing Wood's Structural Integrity

The Challenge: Fire Safety Without Compromising Performance

Traditional fire retardant treated wood has historically raised questions about structural integrity in high-temperature environments like enclosed attics and roof assemblies. In Type I, II, and III construction, specifying fire-rated assemblies requires navigating complex building code requirements while addressing potential risks related to strength degradation, fastener corrosion, and long-term liability.

Beyond code compliance, life safety depends on materials that slow flame spread and reduce smoke development—buying critical evacuation time for occupants and valuable operational time for first responders during fire events. However, when building codes demand enhanced fire protection, but design intent calls for wood’s efficiency, workability, and familiarity, architects are often forced into difficult trade-offs.

Designers need solutions that meet fire code requirements while preserving the construction practicality expected from modern building systems.

One Solution: Code-Compliant Fire Protection with Verified Durability

Kopper’s FlamePRO® Fire Retardant Treated Wood (FRTW) eliminates the tradeoff between code compliance and construction practicality. Pressure-impregnated with Interior Type A High Temperature (HT) fire retardant chemicals, FlamePRO® lumber and plywood deliver proven fire performance while maintaining wood's natural workability and structural integrity.

Some key technical advantages include,

Independent Testing & Certification:

• UL Classified FR-S Rating
• ICC-ESR Report 4244
• CAL FIRE Listed
• ASTM E84 Extended 30-minute test
• AWPA compliant (UC-1, UCFA, T1, P50)

Superior Indoor Air Quality:

• GREENGUARD Gold Certified for low VOC emissions
• SCS Indoor Advantage™ Gold Certified
• Suitable for schools, offices, healthcare facilities

Low Corrosion: ASTM E12 testing confirms minimal corrosion to standard fasteners including galvanized steel, aluminum, copper, and brass when properly sized.

Minimal Hygroscopicity: ASTM D3201 testing confirms FlamePRO® doesn't pick up excessive moisture compared to untreated wood, reducing dimensional instability concerns.

Workability: Maintains natural wood workability with standard carpentry practices. Compatible with latex and oil-based paints, water- and solvent-based stains following standard surface preparation.

Simplified Code Compliance

FlamePRO® meets strict IBC and IRC requirements for FRTW, including AWPA P50 and ICC AC66 standards (ICC-ESR Report 4244), simplifying specification across multi-family residential, commercial, and institutional projects.

The product achieves UL "FR-S" Class A classification with flame spread and smoke development ratings of 25 or less (ASTM E84), slowing fire progression while reducing toxic smoke generation, the leading cause of fire fatalities.

Design Flexibility Through Tested Assemblies

FlamePRO® is supported by 1-hour and 2-hour tested wall assemblies (ASTM E119, ANSI/UL 263), eliminating the need for custom fire-rating engineering. These pre-approved assemblies, covering interior partitions and exterior walls with various facing materials, streamline design and approval processes.

Available in lumber (minimum 2x4 at 16" o.c.) and plywood (minimum 15/32" thick), FlamePRO® adapts to standard construction practices across roof systems, floor assemblies, wall framing, mezzanines, stairways, and architectural millwork.

Verified Long-Term Structural Performance

Tested to ASTM D5664 and D5516, FlamePRO® maintains structural integrity in elevated temperatures up to 150°F for lumber and 170°F for plywood—the elevated conditions in enclosed roof assemblies where heat accumulation causes premature failure in lesser products.

Comprehensive strength design factor tables enable confident specification across multiple climate zones and loading conditions, backed by a 50-Year Limited Warranty against structural failure due to heat or humidity—addressing the long-term liability concerns that make specifiers hesitant about fire retardant treated wood.

Penetrating Protection

Pressure-impregnated throughout the wood, FlamePRO® maintains fire resistance even when cut, drilled, or joined during installation. Standard joining cuts and drilled holes require no field treatment to maintain flame spread ratings, though ripping or extensive milling of lumber is not permitted (plywood can be ripped as required).

Supporting Safer, Stronger, More Sustainable Infrastructure

FlamePRO® advances Koppers' mission by enhancing building safety through verified fire protection, promoting healthier indoor environments through low-VOC formulations, and extending the service life of wood framing systems. This is wood protection that doesn't force compromises—it's proven performance meeting today's codes while addressing tomorrow's durability expectations. Learn more about Koppers on Material Hub.