How to Specify Fire Treated Wood for Your Next Project
Fire treated wood (FRTW) plays a critical role in today’s commercial, multi-family, and code-driven construction environments. Whether you’re building schools, retail structures, hospitality spaces, or residential occupancy requiring fire protection, understanding how to specify fire treated wood early in design can streamline procurement, prevent costly change orders, and ensure code compliance.
If you’re researching how to buy FRTW or preparing a fire treated wood specification, this guide walks through the essential considerations.
1. Start with the Required Fire Performance Rating
Before selecting a product, determine the fire protection performance the structure requires. Key classification categories include:
- Class A (or Class I) surface burning characteristics
- Flame spread index ≤25
- Smoke-developed index ≤450
Most commercial building types and interior applications require Class A compliant FRTW as defined by ASTM E84 or UL 723.
Tip: Always ensure the testing applies to the specific lumber species, thickness, and treatment formulation being used.
2. Confirm Third-Party Code Compliance
All FRTW must meet standards recognized by the International Building Code (IBC) and National Fire Protection Association (NFPA). Look for:
- ICC-ES evaluation report (ER/ESR)
- UL Classification or listing
- Compliance with ASTM D3201 (leachability and hygroscopicity)
At Biewer, our FRTW is pressure-impregnated and verified through third-party audited programs to ensure consistent performance and accurate labeling.
3. Specify the Correct Use Category
Not all fire treated wood can be used in the same environment. Moisture exposure matters.
| Application Type | Required Label |
|---|---|
| Interior dry-use | Interior / Above-grade |
| Limited moisture exposure | Interior with weather shielding |
| Exterior or ground contact | Only if treated and listed for exposed conditions |
Most FRTW is intended only for interior, dry environments unless otherwise labeled.
4. Specify the Lumber Species and Grade
Different wood species absorb chemical preservative differently, which affects final performance. Your fire treated wood specification should include:
- Species group (e.g., SPF, SYP, DFir-L)
- Grade and dimension
- Treatment brand or type
A complete and precise specification helps ensure bids match your project needs and avoids substitutions.
5. Require Certification and Markings on Each Piece
Every piece of code-compliant FRTW must include a legible stamp showing:
- Treating manufacturer
- Compliance report number (ICC-ESR, UL, etc.)
- Intended use (Interior / Exterior, if approved)
- Fire classification rating
These markings confirm the material meets installed project requirements.
6. Understand Storage and Handling Requirements
To protect performance integrity:
- Keep wood dry prior to installation
- Store under cover and off the ground
- Do not cut, notch, or drill unless permitted in specification literature
If field cuts are necessary, refer to the treatment manufacturer’s guidelines — not all FRTW products require or permit field-applied coatings.
Sample Specification Line
Fire Treated Wood: Provide pressure-impregnated fire retardant wood products certified to ICC-ESR requirements and labeled for Interior Use. Product must achieve Class A (Class I) rating in accordance with ASTM E84/UL 723, comply with ASTM D3201 hygroscopic testing, and be stamped for species, use category, and performance classification.
Ready to Buy? Here’s What to Expect
When evaluating bids or learning how to buy FRTW, verify:
- Lead time and availability by species and dimension
- Required documentation (MSDS, ESR reports, testing data, certification letters)
- Specific application approval (sheathing, structural framing, blocking, roof systems, etc.)
Biewer offers fully code-compliant FRTW solutions and technical support to help ensure the right product is selected for the right application — before materials reach the jobsite.
Talk to Our Team
Whether you’re an architect, specifier, engineer, or contractor, the right fire treated wood specification saves time and protects project compliance.
Need help specifying or purchasing fire treated wood?
Our technical team is here to support design professionals and builders from planning to delivery.