Building Code Glossary
Flue Liner (Lining): Building Code Definition
How the IRC 2009, IMC 2009 define flue liner (lining), 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
Flue liner (lining) is a defined term in the International Residential Code (IRC) 2009, in Fuel Gas. The code's own words are: “A system or material used to form the inside surface of a flue in a chimneyor vent, for the purpose of protecting the surrounding structure from the effects of combustion products and for conveying combustion products without leakage to the atmosphere.” The IMC 2009 defines the same term with different wording, so the controlling text depends on which code governs the question in front of you — the comparison below sets the versions side by side. The term is used in 2 chapters of this corpus, most often in Definitions (IMC 2009), Fuel Gas (IRC 2009). These pages transcribe the 2009 model text; verify the definition against the edition and amendments your authority having jurisdiction has adopted.
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?
Flue Liner (Lining) — IRC 2009, Fuel Gas:
A system or material used to form the inside surface of a flue in a chimneyor vent, for the purpose of protecting the surrounding structure from the effects of combustion products and for conveying combustion products without leakage to the atmosphere.
What must be verified before using this guidance?
Two of the I-Codes in this corpus define Flue Liner (Lining), and the wording is not identical — read the version that governs your question.
| Code | Where it is defined | Definition |
|---|---|---|
| IRC 2009 | Fuel Gas | A system or material used to form the inside surface of a flue in a chimneyor vent, for the purpose of protecting the surrounding structure from the effects of combustion products and for conveying combustion products without leakage to the atmosphere. |
| IMC 2009 | Definitions | A system or material used to form the inside surface of a flue in a chimney or vent, for the purpose of protecting the surrounding structure from the effects of combustion products and conveying combustion products without leakage to the atmosphere. |
Where flue liner (lining) is used in the code
The term appears in 2 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.
| Chapter | Code | Mentions |
|---|---|---|
| Definitions | IMC 2009 | 1 |
| Fuel Gas | IRC 2009 | 1 |
The terms flue liner (lining) is built out of
The definition above leans on 5 other defined terms. Each carries its own code definition, and a local amendment to any of them changes what flue liner (lining) covers:
- Combustion Products — IRC 2009: Constituents resulting from the combustion of a fuel with the oxygen of the air, including the inert gases, but excluding excess air.
- Combustion — IRC 2009: In the context of this code, refers to the rapid oxidation of fuel accompanied by the production of heat or heat and light.
- Structure — IPC 2009: That which is built or constructed or a portion thereof.
- Chimney — IBC 2009: A primarily vertical enclosure containing one or more passageways for conveying flue gases to the outside atmosphere.
- System — IFC 2009: An assembly of equipment consisting of a tank, container or containers, appurtenances, pumps, compressors and connecting piping.
Flue Liner (Lining): 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 | Fuel Gas | |
| Read the definition in the adopted IMC | Definitions | |
| Re-check the requirement that uses it | Definitions (IMC 2009) | |
| Re-check the requirement that uses it | Fuel Gas (IRC 2009) | |
| Confirm the dependent definition | Combustion Products | |
| Confirm the dependent definition | Combustion | |
| Confirm the dependent definition | Structure | |
| 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
- Combustion Products: Building Code Definition
- Combustion: Building Code Definition
- Structure: Building Code Definition
- Chimney: 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 flue liner (lining)?
The International Residential Code (IRC) 2009 defines it in Fuel Gas as: “A system or material used to form the inside surface of a flue in a chimneyor vent, for the purpose of protecting the surrounding structure from the effects of combustion products and for conveying combustion products without leakage to the atmosphere.” 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 flue liner (lining)?
In this corpus the term is used across 2 chapters, led by Definitions in the IMC 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.
Is a chimney liner required by code?
Chimney is a separate defined term. The IBC 2009 defines it as: “A primarily vertical enclosure containing one or more passageways for conveying flue gases to the outside atmosphere.” That is not the same as flue liner (lining), which the IRC 2009 defines as “A system or material used to form the inside surface of a flue in a chimneyor vent, for the purpose of protecting the surrounding structure from the effects of combustion products and for conveying combustion products without leakage to the …” — read both before applying either, and confirm the wording in the edition your jurisdiction has adopted.
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