# Alteration: Building Code Definition

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

- Canonical: https://harth.build/resources/glossary/alteration/
- 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, IECC 2009 (2009 editions transcribed in this corpus) |
| Primary source | IBC 2009 Definitions (model text, not a jurisdiction's adopted text) |
| Chapters using the term | 51 (counted across the codes hosted here) |
| Wording identical across codes | No (compare before citing one code's wording under another) |

## Direct answer

Alteration is a defined term in the International Building Code (IBC) 2009, in Definitions. The code's own words are: “Any construction or renovation to an existing structure other than repair or addition.” The IRC 2009 words it differently, in Definitions: “Any construction or renovation to an existing structure other than repair or addition that requires a permit. Also, a change in a mechanical system that involves an extension, addition or change to the arrangement, type or purpose of the original installation that requires a permit.” The IRC 2009, IFC 2009, IMC 2009, IECC 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 51 chapters of this corpus, most often in Existing Structures (IBC 2009), Scope and Administration (IBC 2009), Administration (IECC 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?

**Alteration** — IBC 2009, Definitions:

> Any construction or renovation to an existing structure other than repair or addition.

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

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

## What must be verified before using this guidance?

Five of the I-Codes in this corpus define **Alteration**, 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) | Any construction or renovation to an existing structure other than repair or addition. |
| IRC 2009 | [Definitions](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/definitions.md) | Any construction or renovation to an existing structure other than repair or addition that requires a permit. Also, a change in a mechanical system that involves an extension, addition or change to the arrangement, type or purpose of the original installation that requires a permit. |
| IFC 2009 | [Definitions](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/definitions.md) | Any construction or renovation to an existing structure other than a repair or addition. |
| IMC 2009 | [Definitions](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/definitions.md) | A change in a mechanical system that involves an extension, addition or change to the arrangement, type or purpose of the original installation. |
| IECC 2009 | [Definitions](https://harth.build/resources/building-codes/us-states/maryland/iecc-2009/definitions.md) | Any construction or renovation to an existing structure other than repair or addition that requires a permit. Also, a change in a mechanical system that involves an extension, addition or change to the arrangement, type or purpose of the original installation that requires a permit. |

## Where alteration is used in the code

The term appears in 51 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.

| Chapter | Code | Mentions |
| --- | --- | --- |
| [Existing Structures](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/existing-structures.md) | IBC 2009 | 99 |
| [Scope and Administration](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/scope-and-administration.md) | IBC 2009 | 24 |
| [Administration](https://harth.build/resources/building-codes/us-states/maryland/iecc-2009/administration.md) | IECC 2009 | 21 |
| [Scope and Administration](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/scope-and-administration.md) | IRC 2009 | 20 |
| [Building Planning](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/building-planning.md) | IRC 2009 | 17 |
| [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 | 14 |
| [Scope and Administration](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/scope-and-administration.md) | IFC 2009 | 12 |
| [Scope and Administration](https://harth.build/resources/building-codes/us-states/new-hampshire/ipc-2009/scope-and-administration.md) | IPC 2009 | 12 |
| [Scope and Administration](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/scope-and-administration.md) | IMC 2009 | 10 |
| [Wood](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/wood.md) | IBC 2009 | 9 |
| [Mechanical Administration](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/mechanical-administration.md) | IRC 2009 | 9 |
| [Elevators and Conveying Systems](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/elevators-and-conveying-systems.md) | IBC 2009 | 8 |

_39 further chapters mention the term._

### The term in use

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

> The provisions of this chapter shall control the alteration, repair, addition and change of occupancy of existing structures.

— [IBC 2009 §3401.1](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/existing-structures.md)

> The provisions of this code shall apply to the construction, alteration, movement, enlargement, replacement, repair, equipment, use and occupancy, location, maintenance, removal and demolition of every building or structure or any appurtenances connected or attached to such buildings or structures.

— [IBC 2009 §101.2](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/scope-and-administration.md)

> Except as specified in this chapter, this code shall not be used to require the removal, alteration or abandonment of, nor prevent the continued use and maintenance of, an existing building or building system lawfully in existence at the time of adoption of this code.

— [IECC 2009 §101.4.1](https://harth.build/resources/building-codes/us-states/maryland/iecc-2009/administration.md)


## The terms alteration is built out of

The definition above leans on 5 other defined terms. Each carries its own code definition, and a local amendment to any of them changes what alteration covers:

- **[Existing Structure](https://harth.build/resources/glossary/existing-structure.md)** — IBC 2009: A structure erected prior to the date of adoption of the appropriate code, or one for which a legal building permit has been issued.
- **[Mechanical System](https://harth.build/resources/glossary/mechanical-system.md)** — IRC 2009: A system specifically addressed and regulated in this code and composed of components, devices, appliances and equipment.
- **[Structure](https://harth.build/resources/glossary/structure.md)** — IPC 2009: That which is built or constructed or a portion thereof.
- **[Addition](https://harth.build/resources/glossary/addition.md)** — IBC 2009: An extension or increase in floor area or height of a building or structure.
- **[Existing](https://harth.build/resources/glossary/existing.md)** — IFC 2009: Buildings, facilities or conditions that are already in existence, constructed or officially authorized prior to the adoption of this code.

## Alteration: 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 | |
| Read the definition in the adopted IECC | Definitions | |
| Re-check the requirement that uses it | Existing Structures (IBC 2009) | |
| Re-check the requirement that uses it | Scope and Administration (IBC 2009) | |
| Re-check the requirement that uses it | Administration (IECC 2009) | |
| Re-check the requirement that uses it | Scope and Administration (IRC 2009) | |
| Confirm the dependent definition | Existing Structure | |
| Confirm the dependent definition | Mechanical System | |
| Confirm the dependent definition | Structure | |
| 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)
- [Existing Structure: Building Code Definition](https://harth.build/resources/glossary/existing-structure.md)
- [Mechanical System: Building Code Definition](https://harth.build/resources/glossary/mechanical-system.md)
- [Structure: Building Code Definition](https://harth.build/resources/glossary/structure.md)
- [Existing: Building Code Definition](https://harth.build/resources/glossary/existing.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 alteration?

The International Building Code (IBC) 2009 defines it in Definitions as: “Any construction or renovation to an existing structure other than repair or addition.” 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 alteration the same way?

No. IBC 2009, IRC 2009, IFC 2009, IMC 2009, IECC 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 alteration?

In this corpus the term is used across 51 chapters, led by Existing Structures 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 considered an alteration to a building?

In the 2009 I-Codes hosted here it is a defined term rather than a description. The IBC 2009 states, in Definitions: “Any construction or renovation to an existing structure other than repair or addition.” It is defined in IBC 2009, IRC 2009, IFC 2009, IMC 2009, IECC 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 the legal definition of an alteration?

In the 2009 I-Codes hosted here it is a defined term rather than a description. The IBC 2009 states, in Definitions: “Any construction or renovation to an existing structure other than repair or addition.” It is defined in IBC 2009, IRC 2009, IFC 2009, IMC 2009, IECC 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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