Building Code Glossary
Chimney: Building Code Definition
How the IBC 2009, IRC 2009, IFC 2009, IMC 2009 define chimney, 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
Chimney is a defined term in the International Building Code (IBC) 2009, in Masonry. The code's own words are: “A primarily vertical enclosure containing one or more passageways for conveying flue gases to the outside atmosphere.” The IRC 2009, IFC 2009, IMC 2009 define 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 27 chapters of this corpus, most often in Fuel Gas (IRC 2009), Masonry (IBC 2009), Chimneys and Fireplaces (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?
Chimney — IBC 2009, Masonry:
A primarily vertical enclosure containing one or more passageways for conveying flue gases to the outside atmosphere.
What must be verified before using this guidance?
Four of the I-Codes in this corpus define Chimney, and the wording is not identical — read the version that governs your question.
| Code | Where it is defined | Definition |
|---|---|---|
| IBC 2009 | Masonry | A primarily vertical enclosure containing one or more passageways for conveying flue gases to the outside atmosphere. |
| IRC 2009 | Definitions | A primary vertical structure containing one or more flues, for the purpose of carrying gaseous products of combustion and air from a fuel-burning appliance to the outside atmosphere. |
| IFC 2009 | Definitions | A primarily vertical enclosure containing one or more passageways for conveying flue gases to the outside atmosphere. |
| IMC 2009 | Definitions | A primarily vertical structure containing one or more flues, for the purpose of carrying gaseous products of combustion and air from a fuel-burning appliance to the outdoor atmosphere. |
Where chimney is used in the code
The term appears in 27 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.
| Chapter | Code | Mentions |
|---|---|---|
| Fuel Gas | IRC 2009 | 317 |
| Masonry | IBC 2009 | 204 |
| Chimneys and Fireplaces | IRC 2009 | 168 |
| Chimneys and Vents | IMC 2009 | 123 |
| Chimneys and Vents | IRC 2009 | 84 |
| Building Services and Systems | IFC 2009 | 33 |
| Definitions | IRC 2009 | 33 |
| Definitions | IMC 2009 | 31 |
| Building Planning | IRC 2009 | 22 |
| General Requirements | IFC 2009 | 12 |
| Fire and Smoke Protection Features | IBC 2009 | 10 |
| Wood | IBC 2009 | 6 |
15 further chapters mention the term.
The term in use
How the code actually writes about chimney, quoted from the 2009 text hosted here:
Piping shall not be installed in or through a ducted supply, return or exhaust, or a clothes chute, chimney or gas vent, dumbwaiter or elevator shaft.
Two 3/l6-inch by I-inch (4.8 mm by 25.4 mm) straps shall be embedded a minimum of 12 inches (305 mm) into the chimney.
A masonry heater is a heating appliance constructed of concrete or solid masonry, hereinafter referred to as masonry, which is designed to absorb and store heat from a solid-fuel fire built in the firebox by routing the exhaust gases through internal heat exchange channels in which the flow path downstream of the firebox may include flow in a horizontal or …
The terms chimney 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 chimney covers:
- 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.
- Flue Gases — IRC 2009: Products of combustion plus excess air in appliance flues or heat exchangers.
- Appliance — IRC 2009: Utilization equipment, normally built in standardized sizes or types, that is installed or connected as a unit to perform one or more functions such as clothes washing, air conditioning, food mixing, deep frying, etc.
- Enclosure — IRC 2009: The case or housing of apparatus, or the fence or walls surrounding an installation, to prevent personnel from accidentally contacting energized parts or to protect the equipment from physical damage.
- Structure — IPC 2009: That which is built or constructed or a portion thereof.
Chimney: 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 IBC | Masonry | |
| Read the definition in the adopted IRC | Definitions | |
| Read the definition in the adopted IFC | Definitions | |
| Read the definition in the adopted IMC | Definitions | |
| Re-check the requirement that uses it | Fuel Gas (IRC 2009) | |
| Re-check the requirement that uses it | Masonry (IBC 2009) | |
| Re-check the requirement that uses it | Chimneys and Fireplaces (IRC 2009) | |
| Re-check the requirement that uses it | Chimneys and Vents (IMC 2009) | |
| Confirm the dependent definition | Combustion | |
| Confirm the dependent definition | Flue Gases | |
| Confirm the dependent definition | Appliance | |
| 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
- Flue Gases: Building Code Definition
- Combustion: Building Code Definition
- Structure: Building Code Definition
- Enclosure: 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 chimney?
The International Building Code (IBC) 2009 defines it in Masonry as: “A primarily vertical enclosure containing one or more passageways for conveying flue gases to the outside 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.
Do the I-Codes define chimney the same way?
No. IBC 2009, IRC 2009, IFC 2009, IMC 2009 all define the term, but the wording is not identical, and a difference in wording can change which requirements are triggered. The comparison table above sets the versions side by side so you can read the one that governs your question.
Which parts of the code depend on chimney?
In this corpus the term is used across 27 chapters, led by Fuel Gas in the IRC 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?
In the 2009 I-Codes hosted here it is a defined term rather than a description. The IBC 2009 states, in Masonry: “A primarily vertical enclosure containing one or more passageways for conveying flue gases to the outside atmosphere.” It is defined in IBC 2009, IRC 2009, IFC 2009, IMC 2009. Because it is a defined term, whatever the adopted edition says it means is what every section using it means — so check Chapter 2 of that edition and any local amendment before relying on this wording.
What does IBC mean in building codes?
Building is a separate defined term. The IBC 2009 defines it as: “Any structure used or intended for supporting or sheltering any use or occupancy.” That is not the same as chimney, which the IBC 2009 defines as “A primarily vertical enclosure containing one or more passageways for conveying flue gases to the outside atmosphere.” — read both before applying either, and confirm the wording in the edition your jurisdiction has adopted.
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