Updated 2026-09-07

Building Code Glossary

Through Penetration: Building Code Definition

How the IBC 2009 define through penetration, where the wording differs, and which chapters depend on the term.

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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.

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Direct answer

Through penetration is a defined term in the International Building Code (IBC) 2009, in Fire and Smoke Protection Features. The code's own words are: “An opening that passes through an entire assembly.” No other I-Code in this corpus defines it, so the IBC 2009 definition is the one to work from. The term is used in 4 chapters of this corpus, most often in Fire and Smoke Protection Features (IBC 2009), Duct Systems (IMC 2009), Building Planning (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?

Through Penetration — IBC 2009, Fire and Smoke Protection Features:

An opening that passes through an entire assembly.

Labeled code-term definition diagram: Through Penetration: Building Code Definition — How the IBC 2009 define through penetration, where the wording differs, and which chapters depend on the term.

What must be verified before using this guidance?

Through Penetration is defined once in this corpus, in the Fire and Smoke Protection Features chapter of the International Building Code (IBC) 2009:

An opening that passes through an entire assembly.

Where through penetration 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
Fire and Smoke Protection Features	IBC 2009	29
Duct Systems	IMC 2009	5
Building Planning	IRC 2009	4
Definitions	IBC 2009	1

Through Penetration: 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	Fire and Smoke Protection Features
Re-check the requirement that uses it	Fire and Smoke Protection Features (IBC 2009)
Re-check the requirement that uses it	Duct Systems (IMC 2009)
Re-check the requirement that uses it	Building Planning (IRC 2009)
Re-check the requirement that uses it	Definitions (IBC 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.

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 through penetration?

The International Building Code (IBC) 2009 defines it in Fire and Smoke Protection Features as: “An opening that passes through an entire assembly.” 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 through penetration?

In this corpus the term is used across 4 chapters, led by Fire and Smoke Protection Features 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 a through-penetration firestop system?

Through-penetration Firestop System is a separate defined term. The IBC 2009 defines it as: “An assemblage of specific materials or products that are designed, tested and fire-resistance rated to resist for a prescribed period of time the spread of fire through penetrations. The F and T Irating criteria for penetration firestop systems shall be in accordance with ASTM E …” That is not the same as through penetration, which the IBC 2009 defines as “An opening that passes through an entire assembly.” — read both before applying either, and confirm the wording in the edition your jurisdiction has adopted.

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