# Exterior Wall: Building Code Definition

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

- Canonical: https://harth.build/resources/glossary/exterior-wall/
- 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, IECC 2009 (2009 editions transcribed in this corpus) |
| Primary source | IBC 2009 Exterior Walls (model text, not a jurisdiction's adopted text) |
| Chapters using the term | 63 (counted across the codes hosted here) |
| Wording identical across codes | No (compare before citing one code's wording under another) |

## Direct answer

Exterior wall is a defined term in the International Building Code (IBC) 2009, in Exterior Walls. The code's own words are: “A wall, bearing or nonbearing, that is used as an enclosing wall for a building, other than a fire wall, and that has a slope of 60 degrees (1.05 rad) or greater with the horizontal plane.” The IRC 2009, IFC 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 63 chapters of this corpus, most often in Fire and Smoke Protection Features (IBC 2009), Exterior Walls (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?

**Exterior Wall** — IBC 2009, Exterior Walls:

> A wall, bearing or nonbearing, that is used as an enclosing wall for a building, other than a fire wall, and that has a slope of 60 degrees (1.05 rad) or greater with the horizontal plane.

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

*How the IBC 2009, IRC 2009, IFC 2009, IECC 2009 define exterior wall, 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 **Exterior Wall**, and the wording is not identical — read the version that governs your question.

| Code | Where it is defined | Definition |
| --- | --- | --- |
| IBC 2009 | [Exterior Walls](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/exterior-walls.md) | A wall, bearing or nonbearing, that is used as an enclosing wall for a building, other than a fire wall, and that has a slope of 60 degrees (1.05 rad) or greater with the horizontal plane. |
| IRC 2009 | [Definitions](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/definitions.md) | An above-grade wall that defines the exterior boundaries of a building. Includes between-floor spandrels, peripheral edges of floors, roof and basement knee walls, dormer walls, gable end walls, walls enclosing a mansard roof and basement walls with an average below-grade wall area that is less than 50 percent of the total opaque and nonopaque area of that enclosing side. |
| IFC 2009 | [Definitions](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/definitions.md) | A wall, bearing or nonbearing, that is used as an enclosing wall for a building, other than a fire wall, and that has a slope of 60 degrees (1.05 rad) or greater with the horizontal plane. |
| IECC 2009 | [Definitions](https://harth.build/resources/building-codes/us-states/maryland/iecc-2009/definitions.md) | Walls including both above-grade walls and basement walls. |

## Where exterior wall is used in the code

The term appears in 63 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.

| Chapter | Code | Mentions |
| --- | --- | --- |
| [Fire and Smoke Protection Features](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/fire-and-smoke-protection-features.md) | IBC 2009 | 150 |
| [Exterior Walls](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/exterior-walls.md) | IBC 2009 | 133 |
| [Wall Construction](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/wall-construction.md) | IRC 2009 | 54 |
| [Wall Covering](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/wall-covering.md) | IRC 2009 | 53 |
| [Plastic](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/plastic.md) | IBC 2009 | 45 |
| [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 | 32 |
| [Building Planning](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/building-planning.md) | IRC 2009 | 32 |
| [Roof Assemblies and Rooftop Structures](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/roof-assemblies-and-rooftop-structures.md) | IBC 2009 | 27 |
| [Foundations](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/foundations.md) | IRC 2009 | 23 |
| [Wood](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/wood.md) | IBC 2009 | 22 |
| [Fire Protection Systems](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/fire-protection-systems.md) | IFC 2009 | 22 |
| [Motor Fuel-dispensing Facilities and Repair Garages](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/motor-fuel-dispensing-facilities-and-repair-garages.md) | IFC 2009 | 21 |

_51 further chapters mention the term._

### The term in use

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

> Cornices, eave overhangs, exterior balconies and similar projections extending beyond the exterior wall shall conform to the requirements of this section and Section 1406.

— [IBC 2009 §705.2](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/fire-and-smoke-protection-features.md)

> Exterior walls shall provide the building with a weather-resistant exterior wall envelope.

— [IBC 2009 §1403.2](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/exterior-walls.md)

> Exterior wall coverings shall be capable of resisting the wind pressures listed in Table R30 1.2 (2) adjusted for height and exposure using Table R301.2(3).

— [IRC 2009 §R602.3](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/wall-construction.md)


## The terms exterior wall 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 exterior wall covers:

- **[Above-grade Wall](https://harth.build/resources/glossary/above-grade-wall.md)** — IECC 2009: A wall more than 50 percent above grade and enclosing conditioned space.
- **[Fire Wall](https://harth.build/resources/glossary/fire-wall.md)** — IBC 2009: A fire-resistance-rated wall having protected openings, which restricts the spread of fire and extends continuously from the foundation to or through the roof, with sufficient structural stability under fire conditions to allow collapse of construction on either side without collapse …
- **[Building](https://harth.build/resources/glossary/building.md)** — IBC 2009: Any structure used or intended for supporting or sheltering any use or occupancy.
- **[Basement](https://harth.build/resources/glossary/basement.md)** — IBC 2009: A story that is not a storyabovegrade plane (see "Story above grade plane" in Section 202).
- **[Slope](https://harth.build/resources/glossary/slope.md)** — IRC 2009: The fall (pitch) of a line of pipe in reference to a horizontal plane.

## Exterior Wall: 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 | Exterior Walls | |
| Read the definition in the adopted IRC | Definitions | |
| Read the definition in the adopted IFC | Definitions | |
| Read the definition in the adopted IECC | Definitions | |
| Re-check the requirement that uses it | Fire and Smoke Protection Features (IBC 2009) | |
| Re-check the requirement that uses it | Exterior Walls (IBC 2009) | |
| Re-check the requirement that uses it | Wall Construction (IRC 2009) | |
| Re-check the requirement that uses it | Wall Covering (IRC 2009) | |
| Confirm the dependent definition | Above-grade Wall | |
| Confirm the dependent definition | Fire Wall | |
| 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)
- [Above-grade Wall: Building Code Definition](https://harth.build/resources/glossary/above-grade-wall.md)
- [Fire Wall: Building Code Definition](https://harth.build/resources/glossary/fire-wall.md)
- [Building: Building Code Definition](https://harth.build/resources/glossary/building.md)
- [Basement: Building Code Definition](https://harth.build/resources/glossary/basement.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 exterior wall?

The International Building Code (IBC) 2009 defines it in Exterior Walls as: “A wall, bearing or nonbearing, that is used as an enclosing wall for a building, other than a fire wall, and that has a slope of 60 degrees (1.05 rad) or greater with the horizontal plane.” 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 exterior wall the same way?

No. IBC 2009, IRC 2009, IFC 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 exterior wall?

In this corpus the term is used across 63 chapters, led by Fire and Smoke Protection Features 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 an exterior wall?

In the 2009 I-Codes hosted here it is a defined term rather than a description. The IBC 2009 states, in Exterior Walls: “A wall, bearing or nonbearing, that is used as an enclosing wall for a building, other than a fire wall, and that has a slope of 60 degrees (1.05 rad) or greater with the horizontal plane.” It is defined in IBC 2009, IRC 2009, IFC 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.

### What are the requirements for exterior walls in the California Building Code Chapter 14?

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 exterior wall, which the IBC 2009 defines as “A wall, bearing or nonbearing, that is used as an enclosing wall for a building, other than a fire wall, and that has a slope of 60 degrees (1.05 rad) or greater with the horizontal plane.” — read both before applying either, and confirm the wording in the edition your jurisdiction has adopted.

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