Building Code Glossary
Offset: Building Code Definition
How the IRC 2009, IPC 2009 define offset, 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
Offset is a defined term in the International Residential Code (IRC) 2009, in Definitions. The code's own words are: “A combination of fittings that makes two changes in direction bringing one section of the pipe out of line but into a line parallel with the other section.” The IPC 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 26 chapters of this corpus, most often in Sanitary Drainage (IPC 2009), Fuel Gas (IRC 2009), Wood (IBC 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?
Offset — IRC 2009, Definitions:
A combination of fittings that makes two changes in direction bringing one section of the pipe out of line but into a line parallel with the other section.
What must be verified before using this guidance?
Two of the I-Codes in this corpus define Offset, and the wording is not identical — read the version that governs your question.
| Code | Where it is defined | Definition |
|---|---|---|
| IRC 2009 | Definitions | A combination of fittings that makes two changes in direction bringing one section of the pipe out of line but into a line parallel with the other section. |
| IPC 2009 | Definitions | A combination of approved bends that makes two changes in direction bringing one section of the pipe out of line but into a line parallel with the other section. |
Where offset is used in the code
The term appears in 26 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.
| Chapter | Code | Mentions |
|---|---|---|
| Sanitary Drainage | IPC 2009 | 59 |
| Fuel Gas | IRC 2009 | 28 |
| Wood | IBC 2009 | 23 |
| Wall Construction | IRC 2009 | 21 |
| Building Planning | IRC 2009 | 18 |
| Sanitary Drainage | IRC 2009 | 16 |
| Soils and Foundations | IBC 2009 | 13 |
| Vents | IPC 2009 | 12 |
| Masonry | IBC 2009 | 9 |
| Chimneys and Fireplaces | IRC 2009 | 8 |
| Water Supply and Distribution | IRC 2009 | 8 |
| Foundations | IRC 2009 | 6 |
14 further chapters mention the term.
The term in use
How the code actually writes about offset, quoted from the 2009 text hosted here:
If a horizontal branch connects to the stack within 2 feet (610 mm) above or below a vertical stack offset, and the offset is located more than four branch intervals below the top of the stack, the offset shall be vented in accordance with Section 916.
Type Band L vents sized in accordance with Item 2 or 3 of Section G2427.6.8.1 shall extend in a generally vertical direction with offsets not exceeding 45 degrees (0.79 rad), except that a vent system having not more than one 60-degree (1.04 rad) offset shall be permitted.
Bearing partitions perpendicular to joists shall not be offset from supporting girders, walls or partitions more than the joist depth unless such joists are of sufficient size to carry the additional load.
Offset compared with Offset (Vent)
These two are the closest pair in the 2009 I-Codes: about 81 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 | |
|---|---|
| Offset (IRC 2009) | fittings, makes, pipe |
| Offset (Vent) (IRC 2009) | approved, bends, make, vent |
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 offset and offset (vent).
The terms offset is built out of
The definition above leans on 1 other defined term. Each carries its own code definition, and a local amendment to any of them changes what offset covers:
- Approved — IBC 2009: Acceptable to the code official or authority having jurisdiction.
Offset: 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 | |
| Read the definition in the adopted IPC | Definitions | |
| Re-check the requirement that uses it | Sanitary Drainage (IPC 2009) | |
| Re-check the requirement that uses it | Fuel Gas (IRC 2009) | |
| Re-check the requirement that uses it | Wood (IBC 2009) | |
| Re-check the requirement that uses it | Wall Construction (IRC 2009) | |
| Confirm the dependent definition | Approved | |
| 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
- Approved: Building Code Definition
- Building: Building Code Definition
- Construction Documents: Building Code Definition
- Registered Design Professional: 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 offset?
The International Residential Code (IRC) 2009 defines it in Definitions as: “A combination of fittings that makes two changes in direction bringing one section of the pipe out of line but into a line parallel with the other section.” 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 offset?
In this corpus the term is used across 26 chapters, led by Sanitary Drainage in the IPC 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 the legal definition of an offset?
In the 2009 I-Codes hosted here it is a defined term rather than a description. The IRC 2009 states, in Definitions: “A combination of fittings that makes two changes in direction bringing one section of the pipe out of line but into a line parallel with the other section.” It is defined in IRC 2009, IPC 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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