Building Code Glossary
Fire-retardant-treated Wood: Building Code Definition
How the IRC 2009 define fire-retardant-treated wood, where the wording differs, and which chapters depend on the term.
On this page
Last updated September 7, 2026 · Definitions quoted from the 2009 International Codes as transcribed in this site's building-codes collection, with the source chapter linked for each quotation. Usage counts are computed over the chapters hosted here, one copy per code. The [ICC code library](https://codes.iccsafe.org/codes) publishes the current model text and the [ICC adoption maps](https://www.iccsafe.org/advocacy/code-adoption-maps/) show which edition a jurisdiction has adopted; those sources control.
Direct answer
Fire-retardant-treated wood is a defined term in the International Residential Code (IRC) 2009, in Definitions. The code's own words are: “Pressure-treated lumber and plywood that exhibit reduced surface burning characteristics and resist propagation of fire.” No other I-Code in this corpus defines it, so the IRC 2009 definition is the one to work from. The term is used in 15 chapters of this corpus, most often in Wood (IBC 2009), Roof-ceiling Construction (IRC 2009), Roof Assemblies and Rooftop Structures (IBC 2009). These pages transcribe the 2009 model text; verify the definition against the edition and amendments your authority having jurisdiction has adopted. Record the jurisdiction, the adopted edition, the application date and any local amendment that rewrites the definition before you use it on a live project, because a term redefined by amendment changes every requirement that depends on it.
Content and cited inputs reviewed by Scott Barrington, Harth founder and architectural technology specialist · Published 2026-09-07 · Updated 2026-09-07.
What does this term mean?
Fire-retardant-treated Wood — IRC 2009, Definitions:
Pressure-treated lumber and plywood that exhibit reduced surface burning characteristics and resist propagation of fire.
What must be verified before using this guidance?
Fire-retardant-treated Wood is defined once in this corpus, in the Definitions chapter of the International Residential Code (IRC) 2009:
Pressure-treated lumber and plywood that exhibit reduced surface burning characteristics and resist propagation of fire.
Where fire-retardant-treated wood is used in the code
The term appears in 15 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.
| Chapter | Code | Mentions |
|---|---|---|
| Wood | IBC 2009 | 43 |
| Roof-ceiling Construction | IRC 2009 | 25 |
| Roof Assemblies and Rooftop Structures | IBC 2009 | 19 |
| Building Planning | IRC 2009 | 14 |
| Fire and Smoke Protection Features | IBC 2009 | 10 |
| Exterior Walls | IBC 2009 | 7 |
| Special Detailed Requirements Based on Use and Occupancy | IBC 2009 | 7 |
| Types of Construction | IBC 2009 | 7 |
| Special Construction | IBC 2009 | 3 |
| Definitions | IBC 2009 | 2 |
| Interior Finishes | IBC 2009 | 2 |
| Solar Systems | IMC 2009 | 2 |
3 further chapters mention the term.
The term in use
How the code actually writes about fire-retardant-treated wood, quoted from the 2009 text hosted here:
Fire-retardant-treated wood is any wood product which, when impregnated with chemicals by a pressure process or other means during manufacture, shall have, when tested in accordance with ASTM E 84 or UL 723, a listed flame spread index of 25 or less and show no evidence of significant progressive combustion when the test is continued for an additional20-minute period.
Fire-retardant-treated wood (FRTW) is any wood product which, when impregnated with chemicals by a pressure process or other means during manufacture, shall have, when tested in accordance with ASTM E 84, a listed flame spread index of 25 or less and shows no evidence of significant progressive combustion when the test is continued for an additional 20-minute period.
In addition, fire-retardant-treated wood roof coverings shall be tested in accordance with ASTM D 2898.
Fire-retardant-treated Wood: what to open, and in what order
Every row is a document this term depends on. The ICC code library and the ICC adoption maps cover the middle rows.
| Check | Where | Confirmed |
|---|---|---|
| Read the definition in the adopted IRC | Definitions | |
| Re-check the requirement that uses it | Wood (IBC 2009) | |
| Re-check the requirement that uses it | Roof-ceiling Construction (IRC 2009) | |
| Re-check the requirement that uses it | Roof Assemblies and Rooftop Structures (IBC 2009) | |
| Re-check the requirement that uses it | Building Planning (IRC 2009) | |
| Local amendment to any of the above | Jurisdiction's amendment list |
A research aid, not a code determination. The authority having jurisdiction decides which edition and which amendments apply.
Where can you explore related guidance?
- Explore all glossary guidance
- Building: Building Code Definition
- Construction Documents: Building Code Definition
- Registered Design Professional: Building Code Definition
- Dwelling Unit: Building Code Definition
Sources and method
Definitions quoted from the 2009 International Codes as transcribed in this site's building-codes collection, with the source chapter linked for each quotation. Usage counts are computed over the chapters hosted here, one copy per code. The ICC code library publishes the current model text and the ICC adoption maps show which edition a jurisdiction has adopted; those sources control.
Source links
Frequently asked questions
What is the code definition of fire-retardant-treated wood?
The International Residential Code (IRC) 2009 defines it in Definitions as: “Pressure-treated lumber and plywood that exhibit reduced surface burning characteristics and resist propagation of fire.” The 2009 model text is reproduced here; the definition that binds your project is the one in the edition your jurisdiction has adopted, as amended locally.
Which parts of the code depend on fire-retardant-treated wood?
In this corpus the term is used across 15 chapters, led by Wood in the IBC 2009. Those are the sections whose scope moves if the definition is amended locally, so read them together with Chapter 2 rather than on their own.
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