Updated 2026-09-07

Building Code Glossary

Stack: Building Code Definition

How the IRC 2009, IPC 2009 define stack, 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

Stack is a defined term in the International Residential Code (IRC) 2009, in Definitions. The code's own words are: “Any main vertical DWV line, including offsets, that extends one or more stories as directly as possible to its vent terminal.” The IPC 2009 words it differently, in Definitions: “A general term for any vertical line of soil, waste, vent or inside conductor piping that extends through at least one story with or without offsets.” 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 28 chapters of this corpus, most often in Vents (IPC 2009), Sanitary Drainage (IPC 2009), Vents (IRC 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?

Stack — IRC 2009, Definitions:

Any main vertical DWV line, including offsets, that extends one or more stories as directly as possible to its vent terminal.

Labeled code-term definition diagram: Stack: Building Code Definition — How the IRC 2009, IPC 2009 define stack, where the wording differs, and which chapters depend on the term.

What must be verified before using this guidance?

Two of the I-Codes in this corpus define Stack, and the wording is not identical — read the version that governs your question.

Code	Where it is defined	Definition
IRC 2009	Definitions	Any main vertical DWV line, including offsets, that extends one or more stories as directly as possible to its vent terminal.
IPC 2009	Definitions	A general term for any vertical line of soil, waste, vent or inside conductor piping that extends through at least one story with or without offsets.

Where stack is used in the code

The term appears in 28 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.

Chapter	Code	Mentions
Vents	IPC 2009	114
Sanitary Drainage	IPC 2009	105
Vents	IRC 2009	47
Sanitary Drainage	IRC 2009	39
Definitions	IPC 2009	20
Definitions	IRC 2009	17
Flammable and Combustible Liquids	IFC 2009	16
Masonry	IBC 2009	15
Wall Construction	IRC 2009	11
Fire Protection Systems	IBC 2009	8
Branch Circuit and Feeder Requirements	IRC 2009	7
Fire Protection Systems	IFC 2009	6

16 further chapters mention the term.

The term in use

How the code actually writes about stack, quoted from the 2009 text hosted here:

A vent stack shall be required for every drainage stack that has five branch intervals or more.

— IPC 2009 §903.2

Horizontal branches shall connect to the bases of stacks at a point located not less than 10 times the diameter of the drainage stack downstream from the stack.

— IPC 2009 §704.3

This chapter shall control the minimum diameter of vent pipes, circuit vents, branch vents and individual vents, and the size and length of vents and various aspects of vent stacks and stack vents.

— IRC 2009 §P3101.1

The terms stack 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 stack covers:

Conductor — IPC 2009: A pipe inside the building that conveys storm water from the roof to a storm or combined bUilding drain.
Piping — IRC 2009: Where used in this code, “piping” refers to either pipe or tubing, or both.
Story — IBC 2009: That portion ofa building included between the upper surface of a floor and the upper surface of the floor or roof next above (also see "Basement," "Mezzanine" and Section 502.1).
Waste — IRC 2009: Liquid-borne waste that is free of fecal matter.

Stack: 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	Vents (IPC 2009)
Re-check the requirement that uses it	Sanitary Drainage (IPC 2009)
Re-check the requirement that uses it	Vents (IRC 2009)
Re-check the requirement that uses it	Sanitary Drainage (IRC 2009)
Confirm the dependent definition	Conductor
Confirm the dependent definition	Piping
Confirm the dependent definition	Story
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 stack?

The International Residential Code (IRC) 2009 defines it in Definitions as: “Any main vertical DWV line, including offsets, that extends one or more stories as directly as possible to its vent terminal.” 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 stack?

In this corpus the term is used across 28 chapters, led by Vents 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 a stack in a building?

In the 2009 I-Codes hosted here it is a defined term rather than a description. The IRC 2009 states, in Definitions: “Any main vertical DWV line, including offsets, that extends one or more stories as directly as possible to its vent terminal.” It is defined in IRC 2009, IPC 2009. It is not the same as Building, which the IBC 2009 defines separately as “Any structure used or intended for supporting or sheltering any use or occupancy.” 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 a stack in code?

In the 2009 I-Codes hosted here it is a defined term rather than a description. The IRC 2009 states, in Definitions: “Any main vertical DWV line, including offsets, that extends one or more stories as directly as possible to its vent terminal.” 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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