# Townhouse: Building Code Definition

> How the IBC 2009, IRC 2009, IFC 2009 define townhouse, where the wording differs, and which chapters depend on the term.

- Canonical: https://harth.build/resources/glossary/townhouse/
- 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 | IBC 2009, IRC 2009, IFC 2009 (2009 editions transcribed in this corpus) |
| Primary source | IBC 2009 Definitions (model text, not a jurisdiction's adopted text) |
| Chapters using the term | 18 (counted across the codes hosted here) |
| Wording identical across codes | No (compare before citing one code's wording under another) |

## Direct answer

Townhouse is a defined term in the International Building Code (IBC) 2009, in Definitions. The code's own words are: “A single-family dwelling unit constructed in a group of three or more attached units in which each unit extends from the foundation to roof and with open space on at least two sides.” The IRC 2009, IFC 2009 define 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 18 chapters of this corpus, most often in Building Planning (IRC 2009), Wall Construction (IRC 2009), Foundations (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](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?

**Townhouse** — IBC 2009, Definitions:

> A single-family dwelling unit constructed in a group of three or more attached units in which each unit extends from the foundation to roof and with open space on at least two sides.

![Labeled code-term definition diagram: Townhouse: Building Code Definition](https://efwwel0vyt9vy5so.public.blob.vercel-storage.com/images/glossary/townhouse/diagram-1344.webp)

*How the IBC 2009, IRC 2009, IFC 2009 define townhouse, where the wording differs, and which chapters depend on the term.*

## What must be verified before using this guidance?

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

| Code | Where it is defined | Definition |
| --- | --- | --- |
| IBC 2009 | [Definitions](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/definitions.md) | A single-family dwelling unit constructed in a group of three or more attached units in which each unit extends from the foundation to roof and with open space on at least two sides. |
| IRC 2009 | [Definitions](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/definitions.md) | A single-family dwelling unit constructed in a group of three or more attached units in which each unit extends from foundation to roof and with a yard or public way on at least two sides. |
| IFC 2009 | [Definitions](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/definitions.md) | A single-family dwelling unit constructed in a group of three or more attached units in which each unit extends from the foundation to roof and with open space on at least two sides. |

## Where townhouse is used in the code

The term appears in 18 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.

| Chapter | Code | Mentions |
| --- | --- | --- |
| [Building Planning](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/building-planning.md) | IRC 2009 | 26 |
| [Wall Construction](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/wall-construction.md) | IRC 2009 | 9 |
| [Foundations](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/foundations.md) | IRC 2009 | 8 |
| [Fire Protection Systems](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/fire-protection-systems.md) | IFC 2009 | 4 |
| [Wall Covering](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/wall-covering.md) | IRC 2009 | 4 |
| [Fire Protection Systems](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/fire-protection-systems.md) | IBC 2009 | 3 |
| [Scope and Administration](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/scope-and-administration.md) | IRC 2009 | 3 |
| [Scope and Administration](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/scope-and-administration.md) | IBC 2009 | 2 |
| [Means of Egress](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/means-of-egress.md) | IFC 2009 | 2 |
| [Scope and Administration](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/scope-and-administration.md) | IMC 2009 | 2 |
| [Scope and Administration](https://harth.build/resources/building-codes/us-states/new-hampshire/ipc-2009/scope-and-administration.md) | IPC 2009 | 2 |
| [Definitions](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/definitions.md) | IRC 2009 | 2 |

_6 further chapters mention the term._

### The term in use

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

> Each townhouse shall be considered a separate building and shall be separated by fire-resistance-rated wall assemblies meeting the requirements of Section R302.1 for exterior walls.

— [IRC 2009 §R302.2](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/building-planning.md)

> Pipinginstalled downstream of the point ofdeliveryshall not extend through any townhouse unit other than the unit served by such piping.

— [IRC 2009 §G2415.1](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/fuel-gas.md)


## The terms townhouse is built out of

The definition above leans on 3 other defined terms. Each carries its own code definition, and a local amendment to any of them changes what townhouse covers:

- **[Dwelling Unit](https://harth.build/resources/glossary/dwelling-unit.md)** — IBC 2009: A single unit providing complete, independent living facilities for one or more persons, including permanent provisions for living, sleeping, eating, cooking and sanitation.
- **[Public Way](https://harth.build/resources/glossary/public-way.md)** — IBC 2009: A street, alley or other parcel of land open to the outside air leading to a street, that has been deeded, dedicated or otherwise permanently appropriated to the public for public use and which has a clear width and height …
- **[Dwelling](https://harth.build/resources/glossary/dwelling.md)** — IBC 2009: A building that contains one or two dwelling units used, intended or designed to be used, rented, leased, let or hired out to be occupied for living purposes.

## Townhouse: 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 IBC | Definitions | |
| Read the definition in the adopted IRC | Definitions | |
| Read the definition in the adopted IFC | Definitions | |
| Re-check the requirement that uses it | Building Planning (IRC 2009) | |
| Re-check the requirement that uses it | Wall Construction (IRC 2009) | |
| Re-check the requirement that uses it | Foundations (IRC 2009) | |
| Re-check the requirement that uses it | Fire Protection Systems (IFC 2009) | |
| Confirm the dependent definition | Dwelling Unit | |
| Confirm the dependent definition | Public Way | |
| Confirm the dependent definition | Dwelling | |
| 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)
- [Dwelling Unit: Building Code Definition](https://harth.build/resources/glossary/dwelling-unit.md)
- [Public Way: Building Code Definition](https://harth.build/resources/glossary/public-way.md)
- [Dwelling: Building Code Definition](https://harth.build/resources/glossary/dwelling.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 townhouse?

The International Building Code (IBC) 2009 defines it in Definitions as: “A single-family dwelling unit constructed in a group of three or more attached units in which each unit extends from the foundation to roof and with open space on at least two sides.” 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 townhouse?

In this corpus the term is used across 18 chapters, led by Building Planning in the IRC 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 a townhouse?

In the 2009 I-Codes hosted here it is a defined term rather than a description. The IBC 2009 states, in Definitions: “A single-family dwelling unit constructed in a group of three or more attached units in which each unit extends from the foundation to roof and with open space on at least two sides.” It is defined in IBC 2009, IRC 2009, IFC 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 does IBC mean in building codes?

Building is a separate defined term. The IBC 2009 defines it as: “Any structure used or intended for supporting or sheltering any use or occupancy.” That is not the same as townhouse, which the IBC 2009 defines as “A single-family dwelling unit constructed in a group of three or more attached units in which each unit extends from the foundation to roof and with open space on at least two sides.” — read both before applying either, and confirm the wording in the edition your jurisdiction has adopted.

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