# Aggregate: Building Code Definition

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

- Canonical: https://harth.build/resources/glossary/aggregate/
- 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 (2009 editions transcribed in this corpus) |
| Primary source | IBC 2009 Roof Assemblies and Rooftop Structures (model text, not a jurisdiction's adopted text) |
| Chapters using the term | 56 (counted across the codes hosted here) |
| Wording identical across codes | Single code (compare before citing one code's wording under another) |

## Direct answer

Aggregate is a defined term in the International Building Code (IBC) 2009, in Roof Assemblies and Rooftop Structures. The code's own words are: “In roofing, crushed stone, crushed slag or water-worn gravel used for surfacing for roof coverings.” No other I-Code in this corpus defines it, so the IBC 2009 definition is the one to work from. The term is used in 56 chapters of this corpus, most often in Fire and Smoke Protection Features (IBC 2009), Special Detailed Requirements Based on Use and Occupancy (IBC 2009), General Building Heights and Areas (IBC 2009). These pages transcribe the 2009 model text; verify the definition against the edition and amendments your authority having jurisdiction has adopted. Record the jurisdiction, the adopted edition, the application date and any local amendment that rewrites the definition before you use it on a live project, because a term redefined by amendment changes every requirement that depends on it.

*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?

**Aggregate** — IBC 2009, Roof Assemblies and Rooftop Structures:

> In roofing, crushed stone, crushed slag or water-worn gravel used for surfacing for roof coverings.

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

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

## What must be verified before using this guidance?

**Aggregate** is defined once in this corpus, in the [Roof Assemblies and Rooftop Structures](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/roof-assemblies-and-rooftop-structures.md) chapter of the International Building Code (IBC) 2009:

> In roofing, crushed stone, crushed slag or water-worn gravel used for surfacing for roof coverings.

## Where aggregate is used in the code

The term appears in 56 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 | 61 |
| [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 | 27 |
| [General Building Heights and Areas](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/general-building-heights-and-areas.md) | IBC 2009 | 24 |
| [Flammable and Combustible Liquids](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/flammable-and-combustible-liquids.md) | IFC 2009 | 20 |
| [Semiconductor Fabrication Facilities](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/semiconductor-fabrication-facilities.md) | IFC 2009 | 20 |
| [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 | 19 |
| [Tents and Other Membrane Structures](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/tents-and-other-membrane-structures.md) | IFC 2009 | 17 |
| [Hazardous Materials-general Provisions](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/hazardous-materials-general-provisions.md) | IFC 2009 | 16 |
| [Oxidizers, Oxidizing Gases and Oxidizing Cryogenic Fluids](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/oxidizers-oxidizing-gases-and-oxidizing-cryogenic-fluids.md) | IFC 2009 | 13 |
| [Concrete](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/concrete.md) | IBC 2009 | 12 |
| [Plastic](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/plastic.md) | IBC 2009 | 12 |
| [Scope and Administration](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/scope-and-administration.md) | IFC 2009 | 12 |

_44 further chapters mention the term._

### The term in use

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

> The aggregate width of openings at any floor level shall not exceed 25 percent of the length of the wall.

— [IBC 2009 §706.8](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/fire-and-smoke-protection-features.md)

> The aggregate length of the openings considered to be providing natural ventilation shall constitute a minimum of 40 percent of the perimeter of the tier.

— [IBC 2009 §406.3.3.1](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/special-detailed-requirements-based-on-use-and-occupancy.md)

> Two or more buildings on the same lot shall be regulated as separate buildings or shall be considered as portions of one building if the bUilding height of each building and the aggregate building area of the buildings are within the limitations of table 503 as modified by Sections 504 and 506.

— [IBC 2009 §503.1.2](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/general-building-heights-and-areas.md)

## Aggregate: 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 | Roof Assemblies and Rooftop Structures | |
| Re-check the requirement that uses it | Fire and Smoke Protection Features (IBC 2009) | |
| Re-check the requirement that uses it | Special Detailed Requirements Based on Use and Occupancy (IBC 2009) | |
| Re-check the requirement that uses it | General Building Heights and Areas (IBC 2009) | |
| Re-check the requirement that uses it | Flammable and Combustible Liquids (IFC 2009) | |
| 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)
- [Roof Assembly: Building Code Definition](https://harth.build/resources/glossary/roof-assembly.md)
- [Roof Deck: Building Code Definition](https://harth.build/resources/glossary/roof-deck.md)
- [Roof Covering: Building Code Definition](https://harth.build/resources/glossary/roof-covering.md)
- [Underlayment: Building Code Definition](https://harth.build/resources/glossary/underlayment.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 aggregate?

The International Building Code (IBC) 2009 defines it in Roof Assemblies and Rooftop Structures as: “In roofing, crushed stone, crushed slag or water-worn gravel used for surfacing for roof coverings.” 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 aggregate?

In this corpus the term is used across 56 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 meaning of aggregate in building construction?

In the 2009 I-Codes hosted here it is a defined term rather than a description. The IBC 2009 states, in Roof Assemblies and Rooftop Structures: “In roofing, crushed stone, crushed slag or water-worn gravel used for surfacing for roof coverings.” It is defined in IBC 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 definition of a building according to the International Building Code?

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 aggregate, which the IBC 2009 defines as “In roofing, crushed stone, crushed slag or water-worn gravel used for surfacing for roof coverings.” — read both before applying either, and confirm the wording in the edition your jurisdiction has adopted.

### What does "aggregate" mean in code?

In the 2009 I-Codes hosted here it is a defined term rather than a description. The IBC 2009 states, in Roof Assemblies and Rooftop Structures: “In roofing, crushed stone, crushed slag or water-worn gravel used for surfacing for roof coverings.” It is defined in IBC 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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