Building Code Glossary
Longitudinal Flue Space: Building Code Definition
How the IFC 2009 define longitudinal flue space, 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
Longitudinal flue space is a defined term in the International Fire Code (IFC) 2009, in High-piled Combustible Storage. The code's own words are: “The flue space between rows of storage perpendicular to the direction of loading.” No other I-Code in this corpus defines it, so the IFC 2009 definition is the one to work from. The term is used in 4 chapters of this corpus, most often in Flammable and Combustible Liquids (IFC 2009), Aerosols (IFC 2009), High-piled Combustible Storage (IFC 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?
Longitudinal Flue Space — IFC 2009, High-piled Combustible Storage:
The flue space between rows of storage perpendicular to the direction of loading.
What must be verified before using this guidance?
Longitudinal Flue Space is defined once in this corpus, in the High-piled Combustible Storage chapter of the International Fire Code (IFC) 2009:
The flue space between rows of storage perpendicular to the direction of loading.
Where longitudinal flue space is used in the code
The term appears in 4 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.
| Chapter | Code | Mentions |
|---|---|---|
| Flammable and Combustible Liquids | IFC 2009 | 6 |
| Aerosols | IFC 2009 | 4 |
| High-piled Combustible Storage | IFC 2009 | 2 |
| Definitions | IFC 2009 | 1 |
Longitudinal Flue Space compared with Transverse Flue Space
These two are the closest pair in the 2009 I-Codes: about 75 per cent of their defining words are the same. The code states both and compares neither, so the difference is worth naming.
| Wording unique to it | |
|---|---|
| Longitudinal Flue Space (IFC 2009) | flue, perpendicular |
| Transverse Flue Space (IFC 2009) | parallel |
Everything else in the two definitions is shared. If a project turns on which of the two applies, those words are the whole of the test — and a local amendment that edits one of them without editing the other moves the boundary between longitudinal flue space and transverse flue space.
Longitudinal Flue Space: 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 IFC | High-piled Combustible Storage | |
| Re-check the requirement that uses it | Flammable and Combustible Liquids (IFC 2009) | |
| Re-check the requirement that uses it | Aerosols (IFC 2009) | |
| Re-check the requirement that uses it | High-piled Combustible Storage (IFC 2009) | |
| Re-check the requirement that uses it | Definitions (IFC 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
- High-piled Combustible Storage: Building Code Definition
- Draft Curtain: Building Code Definition
- Commodity: Building Code Definition
- Early Suppression Fast-response (ESFR) Sprinkler: 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 longitudinal flue space?
The International Fire Code (IFC) 2009 defines it in High-piled Combustible Storage as: “The flue space between rows of storage perpendicular to the direction of loading.” 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 longitudinal flue space?
In this corpus the term is used across 4 chapters, led by Flammable and Combustible Liquids in the IFC 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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