Building Code Glossary
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.
On this page
Last updated September 7, 2026 · 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.
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, 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.
What must be verified before using this guidance?
Type B Unit is defined once in this corpus, in the Accessibility 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 | IBC 2009 | 131 |
| Means of Egress | IFC 2009 | 12 |
| Means of Egress | IBC 2009 | 10 |
| Special Construction | IBC 2009 | 8 |
| Existing Structures | IBC 2009 | 2 |
| Definitions | 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.
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 (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 — 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 — 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 — 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 and the ICC 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
- Sleeping Unit: Building Code Definition
- Dwelling Unit: Building Code Definition
- Dwelling: Building Code Definition
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 publishes the current model text and the ICC adoption maps show which edition a jurisdiction has adopted; those sources control.
Source links
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.
Related pages
- Truss Design Drawing: Building Code Definition
Truss Design Drawing — IRC 2009 definition: The graphic depiction of an individual truss, which describes the design and physical characteristics of the …
- Tube Trailer: Building Code Definition
Tube Trailer — IFC 2009 definition: A semitrailer on which a number of tubular gas cylinders have been mounted.
- Type A Unit: Building Code Definition
Type A Unit — IBC 2009 definition: A dwelling unit or sleeping unit designed and constructed for accessibility in accordance with this code …
- Type L Vent: Building Code Definition
Type L Vent — IRC 2009 definition: A listed and labeled vent conforming to UL 641 for venting oil-burning appliances listed for use …
- Unauthorized Discharge: Building Code Definition
Unauthorized Discharge — IFC 2009 definition: A release or emission of materials in a manner which does not conform to the provisions …
- Underlayment: Building Code Definition
Underlayment — IBC 2009 definition: One or more layers of felt, sheathing paper, nonbituminous saturated felt or other approved material over …