# Gross Leasable Area: Building Code Definition > How the IBC 2009 define gross leasable area, where the wording differs, and which chapters depend on the term. - Canonical: https://harth.build/resources/glossary/gross-leasable-area/ - 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 Special Detailed Requirements Based on Use and Occupancy (model text, not a jurisdiction's adopted text) | | Chapters using the term | 2 (counted across the codes hosted here) | | Wording identical across codes | Single code (compare before citing one code's wording under another) | ## Direct answer Gross leasable area is a defined term in the International Building Code (IBC) 2009, in Special Detailed Requirements Based on Use and Occupancy. The code's own words are: “The total floor area designed for tenant occupancy and exclusive use. The area of tenant occupancy is measured from the centerlines of joint partitions to the outside of the tenant walls. All tenant areas, including areas used for storage, shall be included in calculating gross leasable area.” 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 2 chapters of this corpus, most often in Special Detailed Requirements Based on Use and Occupancy (IBC 2009), Definitions (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? **Gross Leasable Area** — IBC 2009, Special Detailed Requirements Based on Use and Occupancy: > The total floor area designed for tenant occupancy and exclusive use. The area of tenant occupancy is measured from the centerlines of joint partitions to the outside of the tenant walls. All tenant areas, including areas used for storage, shall be included in calculating gross leasable area. ![Labeled code-term definition diagram: Gross Leasable Area: Building Code Definition](https://efwwel0vyt9vy5so.public.blob.vercel-storage.com/images/glossary/gross-leasable-area/diagram-1344.webp) *How the IBC 2009 define gross leasable area, where the wording differs, and which chapters depend on the term.* ## What must be verified before using this guidance? **Gross Leasable Area** is defined once in this corpus, in the [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) chapter of the International Building Code (IBC) 2009: > The total floor area designed for tenant occupancy and exclusive use. The area of tenant occupancy is measured from the centerlines of joint partitions to the outside of the tenant walls. All tenant areas, including areas used for storage, shall be included in calculating gross leasable area. ## Where gross leasable area is used in the code The term appears in 2 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next. | Chapter | Code | Mentions | | --- | --- | --- | | [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 | 12 | | [Definitions](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/definitions.md) | IBC 2009 | 1 | ### The term in use How the code actually writes about gross leasable area, quoted from the 2009 text hosted here: > In determining required means of egress of the mall, the number of occupants for whom means of egress are to be provided shall be based on gross leasable area of the covered mall building (excluding anchor bUildings) and the occupant loadfactor as determined by the following equation. — [IBC 2009 §402.4.1.1](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/special-detailed-requirements-based-on-use-and-occupancy.md) ## The terms gross leasable area is built out of The definition above leans on 3 other defined terms. Each carries its own code definition, and a local amendment to any of them changes what gross leasable area covers: - **[Occupancy](https://harth.build/resources/glossary/occupancy.md)** — IMC 2009: The purpose for which a building, or portion thereof, is utilized or occupied. - **[Joint](https://harth.build/resources/glossary/joint.md)** — IBC 2009: The linear opening in or between adjacent fire-resistance-rated assemblies that is designed to allow independent movement of the building in any plane caused by thermal, seismic, wind or any other loading. - **[Shall](https://harth.build/resources/glossary/shall.md)** — IRC 2009: The term, when used in the code, is construed as mandatory. ## Gross Leasable Area: 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 | Special Detailed Requirements Based on Use and Occupancy | | | Re-check the requirement that uses it | Special Detailed Requirements Based on Use and Occupancy (IBC 2009) | | | Re-check the requirement that uses it | Definitions (IBC 2009) | | | Confirm the dependent definition | Occupancy | | | Confirm the dependent definition | Joint | | | Confirm the dependent definition | Shall | | | 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) - [Occupancy: Building Code Definition](https://harth.build/resources/glossary/occupancy.md) - [Joint: Building Code Definition](https://harth.build/resources/glossary/joint.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 gross leasable area? The International Building Code (IBC) 2009 defines it in Special Detailed Requirements Based on Use and Occupancy as: “The total floor area designed for tenant occupancy and exclusive use. The area of tenant occupancy is measured from the centerlines of joint partitions to the outside of the tenant walls. All tenant areas, including areas used for storage, shall be included in calculating gross leasable area.” 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 gross leasable area? In this corpus the term is used across 2 chapters, led by Special Detailed Requirements Based on Use and Occupancy 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 meant by gross leasable area? In the 2009 I-Codes hosted here it is a defined term rather than a description. The IBC 2009 states, in Special Detailed Requirements Based on Use and Occupancy: “The total floor area designed for tenant occupancy and exclusive use. The area of tenant occupancy is measured from the centerlines of joint partitions to the outside of the tenant walls. All tenant areas, including areas used for storage, shall be included in calculating gross leasable area.” 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. ### What is the definition of gross building area? 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 gross leasable area, which the IBC 2009 defines as “The total floor area designed for tenant occupancy and exclusive use. The area of tenant occupancy is measured from the centerlines of joint partitions to the outside of the tenant walls. All tenant areas, including areas used for storage, shall …” — read both before applying either, and confirm the wording in the edition your jurisdiction has adopted. --- - Continue in Harth (open this topic in the Harth agent): https://app.harth.build/agent?context=%2Fresources%2Fglossary%2Fgross-leasable-area%2F - View this page in a browser: https://harth.build/resources/glossary/gross-leasable-area/ - All resources for agents: https://harth.build/llms.txt