# Side Vent: Building Code Definition > How the IRC 2009 define side vent, where the wording differs, and which chapters depend on the term. - Canonical: https://harth.build/resources/glossary/side-vent/ - Last updated: 2026-09-07 - Data source: 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. ## Key facts | Fact | Value | | --- | --- | | Defined in | IRC 2009 (2009 editions transcribed in this corpus) | | Primary source | IRC 2009 Definitions (model text, not a jurisdiction's adopted text) | | Chapters using the term | 4 (counted across the codes hosted here) | | Wording identical across codes | Single code (compare before citing one code's wording under another) | ## Direct answer Side vent is a defined term in the International Residential Code (IRC) 2009, in Definitions. The code's own words are: “A vent connecting to the drain pipe through a fitting at an angle less than 45 degrees (0.79 rad) to the horizontal.” 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 4 chapters of this corpus, most often in Special Detailed Requirements Based on Use and Occupancy (IBC 2009), Vents (IPC 2009), Definitions (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](https://nz.linkedin.com/in/barrington), Harth founder and architectural technology specialist · Published 2026-09-07 · Updated 2026-09-07.* ## What does this term mean? **Side Vent** — IRC 2009, Definitions: > A vent connecting to the drain pipe through a fitting at an angle less than 45 degrees (0.79 rad) to the horizontal. ![Labeled code-term definition diagram: Side Vent: Building Code Definition](https://efwwel0vyt9vy5so.public.blob.vercel-storage.com/images/glossary/side-vent/diagram-1344.webp) *How the IRC 2009 define side vent, where the wording differs, and which chapters depend on the term.* ## What must be verified before using this guidance? **Side Vent** is defined once in this corpus, in the [Definitions](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/definitions.md) chapter of the International Residential Code (IRC) 2009: > A vent connecting to the drain pipe through a fitting at an angle less than 45 degrees (0.79 rad) to the horizontal. ## Where side vent 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 | | --- | --- | --- | | [Special Detailed Requirements Based on Use and Occupancy](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/special-detailed-requirements-based-on-use-and-occupancy.md) | IBC 2009 | 2 | | [Vents](https://harth.build/resources/building-codes/us-states/new-hampshire/ipc-2009/vents.md) | IPC 2009 | 1 | | [Definitions](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/definitions.md) | IRC 2009 | 1 | | [Vents](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/vents.md) | IRC 2009 | 1 | ## Side Vent compared with Horizontal Pipe These two are the closest pair in the 2009 I-Codes: about 50 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 | | --- | --- | | **Side Vent** (IRC 2009) | vent, connecting, drain, through | | [Horizontal Pipe](https://harth.build/resources/glossary/horizontal-pipe.md) (IRC 2009) | makes | 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 side vent and horizontal pipe. ## The terms side vent is built out of The definition above leans on 2 other defined terms. Each carries its own code definition, and a local amendment to any of them changes what side vent covers: - **[Fitting](https://harth.build/resources/glossary/fitting.md)** — IRC 2009: An accessory such as a locknut, bushing or other part of a wiring system that is intended primarily to perform a mechanical rather than an electrical function. - **[Drain](https://harth.build/resources/glossary/drain.md)** — IRC 2009: Any pipe that carries soil and water-borne wastes in a building drainage system. ## Side Vent: what to open, and in what order Every row is a document this term depends on. The [ICC code library](https://codes.iccsafe.org/codes) and the [ICC adoption maps](https://www.iccsafe.org/advocacy/code-adoption-maps/) cover the middle rows. | Check | Where | Confirmed | | --- | --- | --- | | Read the definition in the adopted IRC | Definitions | | | Re-check the requirement that uses it | Special Detailed Requirements Based on Use and Occupancy (IBC 2009) | | | Re-check the requirement that uses it | Vents (IPC 2009) | | | Re-check the requirement that uses it | Definitions (IRC 2009) | | | Re-check the requirement that uses it | Vents (IRC 2009) | | | Confirm the dependent definition | Fitting | | | Confirm the dependent definition | Drain | | | 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](https://harth.build/resources/glossary.md) - [Fitting: Building Code Definition](https://harth.build/resources/glossary/fitting.md) - [Drain: Building Code Definition](https://harth.build/resources/glossary/drain.md) ## 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](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. ### Source links - [codes.iccsafe.org](https://codes.iccsafe.org/codes) - [iccsafe.org](https://www.iccsafe.org/advocacy/code-adoption-maps/) ## Frequently asked questions ### What is the code definition of side vent? The International Residential Code (IRC) 2009 defines it in Definitions as: “A vent connecting to the drain pipe through a fitting at an angle less than 45 degrees (0.79 rad) to the horizontal.” 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 side vent? In this corpus the term is used across 4 chapters, led by Special Detailed Requirements Based on Use and Occupancy 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 side vent? In the 2009 I-Codes hosted here it is a defined term rather than a description. The IRC 2009 states, in Definitions: “A vent connecting to the drain pipe through a fitting at an angle less than 45 degrees (0.79 rad) to the horizontal.” 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. ### What is side wall venting? Venting is a separate defined term. The IRC 2009 defines it as: “Removal of combustion products to the outdoors.” That is not the same as side vent, which the IRC 2009 defines as “A vent connecting to the drain pipe through a fitting at an angle less than 45 degrees (0.79 rad) to the horizontal.” — read both before applying either, and confirm the wording in the edition your jurisdiction has adopted. --- - Continue in Harth (open this topic in the Harth agent): https://app.harth.build/agent?context=%2Fresources%2Fglossary%2Fside-vent%2F - View this page in a browser: https://harth.build/resources/glossary/side-vent/ - All resources for agents: https://harth.build/llms.txt