# Dwelling: Building Code Definition

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

- Canonical: https://harth.build/resources/glossary/dwelling/
- 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, IMC 2009 (2009 editions transcribed in this corpus) |
| Primary source | IBC 2009 Definitions (model text, not a jurisdiction's adopted text) |
| Chapters using the term | 84 (counted across the codes hosted here) |
| Wording identical across codes | No (compare before citing one code's wording under another) |

## Direct answer

Dwelling is a defined term in the International Building Code (IBC) 2009, in Definitions. The code's own words are: “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.” The IRC 2009, IFC 2009, IMC 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 84 chapters of this corpus, most often in Means of Egress (IBC 2009), Means of Egress (IFC 2009), Accessibility (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](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?

**Dwelling** — IBC 2009, Definitions:

> 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.

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

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

## What must be verified before using this guidance?

Four of the I-Codes in this corpus define **Dwelling**, 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 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. |
| IRC 2009 | [Definitions](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/definitions.md) | Any building that contains one or two dwelling units used, intended, or designed to be built, used, rented, leased, let or hired out to be occupied, or that are occupied for living purposes. |
| IFC 2009 | [Definitions](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/definitions.md) | 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. |
| IMC 2009 | [Definitions](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/definitions.md) | A building or portion thereof that contains not more than two dwelling units. |

## Where dwelling is used in the code

The term appears in 84 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.

| Chapter | Code | Mentions |
| --- | --- | --- |
| [Means of Egress](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/means-of-egress.md) | IBC 2009 | 146 |
| [Means of Egress](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/means-of-egress.md) | IFC 2009 | 132 |
| [Accessibility](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/accessibility.md) | IBC 2009 | 93 |
| [Building Planning](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/building-planning.md) | IRC 2009 | 80 |
| [Fire Protection Systems](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/fire-protection-systems.md) | IFC 2009 | 68 |
| [Fire Protection Systems](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/fire-protection-systems.md) | IBC 2009 | 66 |
| [Fire and Smoke Protection Features](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/fire-and-smoke-protection-features.md) | IBC 2009 | 52 |
| [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 | 35 |
| [Existing Structures](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/existing-structures.md) | IBC 2009 | 27 |
| [Water Supply and Distribution](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/water-supply-and-distribution.md) | IRC 2009 | 27 |
| [Wall Construction](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/wall-construction.md) | IRC 2009 | 24 |
| [Construction Requirements for Existing Buildings](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/construction-requirements-for-existing-buildings.md) | IFC 2009 | 23 |

_72 further chapters mention the term._

### The term in use

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

> Thresholds at doorways shall not exceed ¾ inch (19.1 mm) in height for sliding doors serving dwelling units or ½ inch (12.7 mm) for other doors.

— [IBC 2009 §1008.1.7](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/means-of-egress.md)

> Windertreads are not permitted in means of egress stairways except within a dwelling unit.

— [IFC 2009 §1009.4.3](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/means-of-egress.md)

> Where a day care facility (Groups A-3, E, 1-4 and R-3) is part of a dwelling unit, only the portion ofthe structure utilized for the day care facility is required to be accessible.

— [IBC 2009 §1103.2.12](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/accessibility.md)


## The terms dwelling 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 dwelling covers:

- **[Building](https://harth.build/resources/glossary/building.md)** — IBC 2009: Any structure used or intended for supporting or sheltering any use or occupancy.

## Dwelling: 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 | |
| Read the definition in the adopted IMC | Definitions | |
| Re-check the requirement that uses it | Means of Egress (IBC 2009) | |
| Re-check the requirement that uses it | Means of Egress (IFC 2009) | |
| Re-check the requirement that uses it | Accessibility (IBC 2009) | |
| Re-check the requirement that uses it | Building Planning (IRC 2009) | |
| Confirm the dependent definition | Building | |
| 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)
- [Building: Building Code Definition](https://harth.build/resources/glossary/building.md)
- [Construction Documents: Building Code Definition](https://harth.build/resources/glossary/construction-documents.md)
- [Registered Design Professional: Building Code Definition](https://harth.build/resources/glossary/registered-design-professional.md)
- [Dwelling Unit: Building Code Definition](https://harth.build/resources/glossary/dwelling-unit.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 dwelling?

The International Building Code (IBC) 2009 defines it in Definitions as: “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.” 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.

### Do the I-Codes define dwelling the same way?

No. IBC 2009, IRC 2009, IFC 2009, IMC 2009 all define the term, but the wording is not identical, and a difference in wording can change which requirements are triggered. The comparison table above sets the versions side by side so you can read the one that governs your question.

### Which parts of the code depend on dwelling?

In this corpus the term is used across 84 chapters, led by Means of Egress 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 the NEC definition of a dwelling unit?

In the 2009 I-Codes hosted here it is a defined term rather than a description. The IBC 2009 states, in Definitions: “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.” It is defined in IBC 2009, IRC 2009, IFC 2009, IMC 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 dwelling, which the IBC 2009 defines as “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.” — read both before applying either, and confirm the wording in the edition your jurisdiction has adopted.

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