Building Code Glossary
Masonry Chimney: Building Code Definition
How the IRC 2009 define masonry 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
Masonry chimney is a defined term in the International Residential Code (IRC) 2009, in Definitions. The code's own words are: “A field-constructed chimney composed of solid masonry units, bricks, stones or concrete.” 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 13 chapters of this corpus, most often in Masonry (IBC 2009), Chimneys and Fireplaces (IRC 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. 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?
Masonry Chimney — IRC 2009, Definitions:
A field-constructed chimney composed of solid masonry units, bricks, stones or concrete.
What must be verified before using this guidance?
Masonry Chimney is defined once in this corpus, in the Definitions chapter of the International Residential Code (IRC) 2009:
A field-constructed chimney composed of solid masonry units, bricks, stones or concrete.
Where masonry chimney is used in the code
The term appears in 13 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.
| Chapter | Code | Mentions |
|---|---|---|
| Masonry | IBC 2009 | 66 |
| Chimneys and Fireplaces | IRC 2009 | 35 |
| Fuel Gas | IRC 2009 | 34 |
| Chimneys and Vents | IMC 2009 | 26 |
| Chimneys and Vents | IRC 2009 | 19 |
| Building Planning | IRC 2009 | 8 |
| Building Services and Systems | IFC 2009 | 5 |
| Mechanical Systems | IBC 2009 | 3 |
| Definitions | IRC 2009 | 3 |
| Fire and Smoke Protection Features | IBC 2009 | 2 |
| Structural Tests and Special Inspections | IBC 2009 | 2 |
| Definitions | IMC 2009 | 2 |
1 further chapters mention the term.
The term in use
How the code actually writes about masonry chimney, quoted from the 2009 text hosted here:
Seismic reinforcing shall not be required within the body of a masonry heater with a height that is equal to or less than 3.5 times its body width and where the masonry chimney serving the heater is not supported by the body of the heater.
Seismic reinforcing shall not be required within the body of a masonry heater whose height is equal to or less than 3.5 times it's body width and where the masonry chimney serving the heater is not supported by the body of the heater.
Masonry chimney flues shall be provided with a cleanout opening having a minimum height of 6 inches (152 mm).
The terms masonry chimney is built out of
The definition above leans on 4 other defined terms. Each carries its own code definition, and a local amendment to any of them changes what masonry chimney covers:
- Solid Masonry — IRC 2009: Load-bearing or nonload-bearing construction using masonry units where the net cross-sectional area of each unit in any plane parallel to the bearing surface is not less than 75 percent of its gross cross-sectional area.
- Chimney — IBC 2009: A primarily vertical enclosure containing one or more passageways for conveying flue gases to the outside atmosphere.
- Masonry — IBC 2009: A built-up construction or combination of building units or materials of clay, shale, concrete, glass, gypsum, stone or other approved units bonded together with or without mortar or grout or other accepted methods of joining.
- Solid — IBC 2009: A material that has a melting point, decomposes or sublimes at a temperature greater than 68°F (20°C).
Masonry 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 IRC | Definitions | |
| 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 | Fuel Gas (IRC 2009) | |
| Re-check the requirement that uses it | Chimneys and Vents (IMC 2009) | |
| Confirm the dependent definition | Solid Masonry | |
| Confirm the dependent definition | Chimney | |
| Confirm the dependent definition | Masonry | |
| 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
- Solid Masonry: Building Code Definition
- Masonry: Building Code Definition
- Chimney: Building Code Definition
- Solid: 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 masonry chimney?
The International Residential Code (IRC) 2009 defines it in Definitions as: “A field-constructed chimney composed of solid masonry units, bricks, stones or concrete.” 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 masonry chimney?
In this corpus the term is used across 13 chapters, led by Masonry 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.
What is considered a masonry chimney?
In the 2009 I-Codes hosted here it is a defined term rather than a description. The IRC 2009 states, in Definitions: “A field-constructed chimney composed of solid masonry units, bricks, stones or concrete.” It is defined in IRC 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.
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