Fire Treated Wood FAQ: Everything You Need to Know
As fire safety requirements continue to evolve, more architects, engineers, and builders are turning to fire treated wood (FRTW) as a reliable solution for code-driven construction. But with multiple product types, testing requirements, labeling rules, and installation considerations, it’s natural to have questions before specifying or ordering material.
This Fire Treated Wood FAQ covers the most common questions about FRTW so you can design, purchase, and install with confidence—while supporting compliance from the first submittal to final inspection.
What is Fire Treated Wood?
Fire treated wood is lumber that has been pressure-impregnated with fire retardant chemicals. These chemicals react within the wood fibers, reducing flammability and slowing the spread of flames and smoke during a fire event.
Is Fire Treated Wood Code Compliant?
Yes—when properly tested, labeled, and certified.
To be used in code-regulated applications, FRTW must:
- Meet Class A (Class I) fire performance per ASTM E84 or UL 723
- Follow applicable IBC/NFPA requirements
- Carry a valid third-party evaluation report (such as an ICC-ESR)
- Be stamped with product, performance, and use designation
Biewer FRTW is fully third-party verified and compliant with national building codes.
Where Can Fire Treated Wood Be Used?
Common approved applications include:
- Wall assemblies
- Floor and roof sheathing
- Blocking and furring strips
- Interior framing
- Attics and concealed spaces
- Load-bearing and non-load-bearing assemblies (when approved)
- Roof trusses
- Rafters
- Plywood roof sheathing
- Floor & roof joists
- Mezzanines
- Sill plates
- Steps
- Stairways
- Studs
- Interior partitions (non-load)
- Plywood
- Subflooring
- Partition walls
- Beams & purlins
- Platforms
- Stages
- Wall sheathing & paneling
- Architectural millwork & trim
- Backing for electrical panels
Always confirm allowed uses based on the specific product listing and evaluation report.
Can Fire Treated Wood Be Used Outdoors?
Most FRTW is intended for interior dry use only. However, certain products may be approved for exterior or weather-exposed applications if clearly labeled as such.
If the stamp does not say “Exterior,” assume it is for interior use.
Does Cutting or Drilling Affect Performance?
Minor field cuts (trimming, notching, or drilling) are generally permitted—but only if the treatment manufacturer guidelines allow it.
Some products require no additional coating, while others may require a field-applied sealant on cuts. Always follow the specific documentation included with your treated wood.
Is Fire Treated Wood Corrosive to Fasteners?
Fire retardant chemicals can change wood pH, so it’s important to pair FRTW with the correct hardware. Most products require:
- Corrosion-resistant fasteners
- Hot-dipped galvanized or stainless steel hardware (depending on exposure)
Refer to the treatment manufacturer’s compatibility tables when selecting fasteners.
Does Fire Treating Affect Strength?
Fire retardant treatment may impact strength values under certain temperature and moisture conditions. For structural use, always rely on:
- The treating manufacturer’s design value tables
- The evaluation report requirements
- IBC and engineering guidance
Biewer FRTW is tested and approved for load-bearing use when installed per engineered design.
What Documentation Should I Expect When Ordering FRTW?
A complete order typically includes:
- ICC-ES evaluation report
- Safety Data Sheet (SDS)
- Product specifications
- Storage and handling instructions
- Installation or engineering guidance (as applicable)
Keeping this documentation on file helps ensure inspection and compliance go smoothly.
How Should Fire Treated Wood Be Stored?
To maintain its fire-resistant properties:
- Keep the material dry prior to installation
- Store it under cover and off the ground
- Do not allow prolonged exposure to moisture
Proper jobsite care preserves code compliance and long-term performance.
Ready to Purchase Fire Treated Wood?
Understanding fire treated wood specifications upfront helps prevent delays, substitutions, inspection issues, and rework.
Whether you’re specifying material for a new design or evaluating bids, Biewer’s FRTW team provides:
- Technical support
- Code compliance guidance
- Documentation packages
- Availability and lead time planning
Let’s Get Your Project Right—From the Start.
Interested in ordering or need help with specification language?
Our technical specialists are here to support architects, engineers, distributors, and contractors throughout the build process.