# Type B Unit: Building Code Definition > How the IBC 2009 define type b unit, where the wording differs, and which chapters depend on the term. - Canonical: https://harth.build/resources/glossary/type-b-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 (2009 editions transcribed in this corpus) | | Primary source | IBC 2009 Accessibility (model text, not a jurisdiction's adopted text) | | Chapters using the term | 6 (counted across the codes hosted here) | | Wording identical across codes | Single code (compare before citing one code's wording under another) | ## Direct answer Type B unit is a defined term in the International Building Code (IBC) 2009, in Accessibility. The code's own words are: “A dwelling unit or sleeping unit designed and constructed for accessibility in accordance with this code and the provisions for Type B units in ICC Al17.1, consistent with the design and construction requirements of the federal Fair Housing Act.” 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 6 chapters of this corpus, most often in Accessibility (IBC 2009), Means of Egress (IFC 2009), Means of Egress (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? **Type B Unit** — IBC 2009, Accessibility: > A dwelling unit or sleeping unit designed and constructed for accessibility in accordance with this code and the provisions for Type B units in ICC Al17.1, consistent with the design and construction requirements of the federal Fair Housing Act. ![Labeled code-term definition diagram: Type B Unit: Building Code Definition](https://efwwel0vyt9vy5so.public.blob.vercel-storage.com/images/glossary/type-b-unit/diagram-1344.webp) *How the IBC 2009 define type b unit, where the wording differs, and which chapters depend on the term.* ## What must be verified before using this guidance? **Type B Unit** is defined once in this corpus, in the [Accessibility](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/accessibility.md) chapter of the International Building Code (IBC) 2009: > A dwelling unit or sleeping unit designed and constructed for accessibility in accordance with this code and the provisions for Type B units in ICC Al17.1, consistent with the design and construction requirements of the federal Fair Housing Act. ## Where type b unit is used in the code The term appears in 6 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next. | Chapter | Code | Mentions | | --- | --- | --- | | [Accessibility](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/accessibility.md) | IBC 2009 | 131 | | [Means of Egress](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/means-of-egress.md) | IFC 2009 | 12 | | [Means of Egress](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/means-of-egress.md) | IBC 2009 | 10 | | [Special Construction](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/special-construction.md) | IBC 2009 | 8 | | [Existing Structures](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/existing-structures.md) | IBC 2009 | 2 | | [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 type b unit, quoted from the 2009 text hosted here: > At least one accessible route shall connect accessible building or facility entrances with the primary entrance of each Accessible unit, Type A unit and Type B unit within the building or facility and with those exterior and interior spaces and facilities that serve the units. — [IBC 2009 §1107.4](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/accessibility.md) ## Type B Unit compared with Type A Unit These two are the closest pair in the 2009 I-Codes: about 69 per cent of their defining words are the same. The code states both and compares neither, so the difference is worth naming. | | Wording unique to it | | --- | --- | | **Type B Unit** (IBC 2009) | b, consistent, design, construction, requirements, federal, fair, housing, act | | [Type A Unit](https://harth.build/resources/glossary/type-a-unit.md) (IBC 2009) | — no wording of its own | Everything else in the two definitions is shared. If a project turns on which of the two applies, those words are the whole of the test — and a local amendment that edits one of them without editing the other moves the boundary between type B unit and type A unit. ## The terms type B unit 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 type B unit covers: - **[Dwelling Unit](https://harth.build/resources/glossary/dwelling-unit.md)** — IBC 2009: A single unit providing complete, independent living facilities for one or more persons, including permanent provisions for living, sleeping, eating, cooking and sanitation. - **[Sleeping Unit](https://harth.build/resources/glossary/sleeping-unit.md)** — IBC 2009: A room or space in which people sleep, which can also include permanent provisions for living, eating, and either sanitation or kitchen facilities but not both. - **[Dwelling](https://harth.build/resources/glossary/dwelling.md)** — IBC 2009: A building that contains one or two dwelling units used, intended or designed to be used, rented, leased, let or hired out to be occupied for living purposes. ## Type B 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 | Accessibility | | | Re-check the requirement that uses it | Accessibility (IBC 2009) | | | Re-check the requirement that uses it | Means of Egress (IFC 2009) | | | Re-check the requirement that uses it | Means of Egress (IBC 2009) | | | Re-check the requirement that uses it | Special Construction (IBC 2009) | | | Confirm the dependent definition | Dwelling Unit | | | Confirm the dependent definition | Sleeping Unit | | | Confirm the dependent definition | Dwelling | | | 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) - [Sleeping Unit: Building Code Definition](https://harth.build/resources/glossary/sleeping-unit.md) - [Dwelling Unit: Building Code Definition](https://harth.build/resources/glossary/dwelling-unit.md) - [Dwelling: Building Code Definition](https://harth.build/resources/glossary/dwelling.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 type b unit? The International Building Code (IBC) 2009 defines it in Accessibility as: “A dwelling unit or sleeping unit designed and constructed for accessibility in accordance with this code and the provisions for Type B units in ICC Al17.1, consistent with the design and construction requirements of the federal Fair Housing Act.” 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 type b unit? In this corpus the term is used across 6 chapters, led by Accessibility 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 a type B unit? In the 2009 I-Codes hosted here it is a defined term rather than a description. The IBC 2009 states, in Accessibility: “A dwelling unit or sleeping unit designed and constructed for accessibility in accordance with this code and the provisions for Type B units in ICC Al17.1, consistent with the design and construction requirements of the federal Fair Housing Act.” 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. --- - Continue in Harth (open this topic in the Harth agent): https://app.harth.build/agent?context=%2Fresources%2Fglossary%2Ftype-b-unit%2F - View this page in a browser: https://harth.build/resources/glossary/type-b-unit/ - All resources for agents: https://harth.build/llms.txt