# Masonry Unit: Building Code Definition

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

- Canonical: https://harth.build/resources/glossary/masonry-unit/
- 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 (2009 editions transcribed in this corpus) |
| Primary source | IBC 2009 Masonry (model text, not a jurisdiction's adopted text) |
| Chapters using the term | 13 (counted across the codes hosted here) |
| Wording identical across codes | No (compare before citing one code's wording under another) |

## Direct answer

Masonry unit is a defined term in the International Building Code (IBC) 2009, in Masonry. The code's own words are: “Brick, tile, stone, glass block or concrete block conforming to the requirements specified in Section 2103.” The IRC 2009 words it differently, in Definitions: “Brick, tile, stone, glass block or concrete block conforming to the requirements specified in Section 2103 of the International BUilding Code.” The IRC 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 13 chapters of this corpus, most often in Masonry (IBC 2009), Fire and Smoke Protection Features (IBC 2009), Wall Construction (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?

**Masonry Unit** — IBC 2009, Masonry:

> Brick, tile, stone, glass block or concrete block conforming to the requirements specified in Section 2103.

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

*How the IBC 2009, IRC 2009 define masonry unit, 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 **Masonry Unit**, and the wording is not identical — read the version that governs your question.

| Code | Where it is defined | Definition |
| --- | --- | --- |
| IBC 2009 | [Masonry](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/masonry.md) | Brick, tile, stone, glass block or concrete block conforming to the requirements specified in Section 2103. |
| IRC 2009 | [Definitions](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/definitions.md) | Brick, tile, stone, glass block or concrete block conforming to the requirements specified in Section 2103 of the International BUilding Code. |

## Where masonry unit is used in the code

The term appears in 13 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.

| Chapter | Code | Mentions |
| --- | --- | --- |
| [Masonry](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/masonry.md) | IBC 2009 | 93 |
| [Fire and Smoke Protection Features](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/fire-and-smoke-protection-features.md) | IBC 2009 | 65 |
| [Wall Construction](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/wall-construction.md) | IRC 2009 | 25 |
| [Soils and Foundations](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/soils-and-foundations.md) | IBC 2009 | 21 |
| [Definitions](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/definitions.md) | IRC 2009 | 15 |
| [Chimneys and Fireplaces](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/chimneys-and-fireplaces.md) | IRC 2009 | 7 |
| [Fuel Gas](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/fuel-gas.md) | IRC 2009 | 6 |
| [Definitions](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/definitions.md) | IMC 2009 | 4 |
| [Commercial Energy Efficiency](https://harth.build/resources/building-codes/us-states/maryland/iecc-2009/commercial-energy-efficiency.md) | IECC 2009 | 2 |
| [Foundations](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/foundations.md) | IRC 2009 | 2 |
| [Definitions](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/definitions.md) | IBC 2009 | 1 |
| [Exterior Walls](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/exterior-walls.md) | IBC 2009 | 1 |

_1 further chapters mention the term._

### The term in use

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

> Te shall be the value obtained for the concrete masonry unit determined in accordance with ASTM C 140.

— [IBC 2009 §721.3.1.2](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/fire-and-smoke-protection-features.md)

> The area of the surface of a masonry unit that is in contact with mortar in the plane of the joint.

— [IBC 2009, Masonry](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/masonry.md)


## The terms masonry unit 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 masonry unit covers:

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

## Masonry Unit: 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 | Masonry | |
| Read the definition in the adopted IRC | Definitions | |
| Re-check the requirement that uses it | Masonry (IBC 2009) | |
| Re-check the requirement that uses it | Fire and Smoke Protection Features (IBC 2009) | |
| Re-check the requirement that uses it | Wall Construction (IRC 2009) | |
| Re-check the requirement that uses it | Soils and Foundations (IBC 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)
- [Chimney: Building Code Definition](https://harth.build/resources/glossary/chimney.md)
- [Tile: Building Code Definition](https://harth.build/resources/glossary/tile.md)
- [Fireplace: Building Code Definition](https://harth.build/resources/glossary/fireplace.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 masonry unit?

The International Building Code (IBC) 2009 defines it in Masonry as: “Brick, tile, stone, glass block or concrete block conforming to the requirements specified in Section 2103.” 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 masonry unit?

In this corpus the term is used across 13 chapters, led by Masonry 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 definition of a masonry unit?

In the 2009 I-Codes hosted here it is a defined term rather than a description. The IBC 2009 states, in Masonry: “Brick, tile, stone, glass block or concrete block conforming to the requirements specified in Section 2103.” It is defined in IBC 2009, 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 considered a masonry building?

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 masonry unit, which the IBC 2009 defines as “Brick, tile, stone, glass block or concrete block conforming to the requirements specified in Section 2103.” — read both before applying either, and confirm the wording in the edition your jurisdiction has adopted.

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