# AAC Masonry: Building Code Definition > How the IBC 2009 define aac masonry, where the wording differs, and which chapters depend on the term. - Canonical: https://harth.build/resources/glossary/aac-masonry/ - 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 Masonry (model text, not a jurisdiction's adopted text) | | Chapters using the term | 3 (counted across the codes hosted here) | | Wording identical across codes | Single code (compare before citing one code's wording under another) | ## Direct answer AAC masonry is a defined term in the International Building Code (IBC) 2009, in Masonry. The code's own words are: “Masonry made of autoclaved aerated concrete (AAC) units, manufactured without internal reinforcement and bonded together using thin- or thick-bed mortar.” 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 3 chapters of this corpus, most often in Masonry (IBC 2009), Structural Design (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. 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? **AAC Masonry** — IBC 2009, Masonry: > Masonry made of autoclaved aerated concrete (AAC) units, manufactured without internal reinforcement and bonded together using thin- or thick-bed mortar. ![Labeled code-term definition diagram: AAC Masonry: Building Code Definition](https://efwwel0vyt9vy5so.public.blob.vercel-storage.com/images/glossary/aac-masonry/diagram-1344.webp) *How the IBC 2009 define aac masonry, where the wording differs, and which chapters depend on the term.* ## What must be verified before using this guidance? **AAC Masonry** is defined once in this corpus, in the [Masonry](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/masonry.md) chapter of the International Building Code (IBC) 2009: > Masonry made of autoclaved aerated concrete (AAC) units, manufactured without internal reinforcement and bonded together using thin- or thick-bed mortar. ## Where aac masonry is used in the code The term appears in 3 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next. | Chapter | Code | Mentions | | --- | --- | --- | | [Masonry](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/masonry.md) | IBC 2009 | 26 | | [Structural Design](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/structural-design.md) | IBC 2009 | 8 | | [Definitions](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/definitions.md) | IBC 2009 | 2 | ### The term in use How the code actually writes about aac masonry, quoted from the 2009 text hosted here: > AAC masonry units shall conform to ASTM C 1386 for the strength class specified. — [IBC 2009 §2103.3](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/masonry.md) > f'AAC = Specified compressive strength of AAC masonry, the minimum compressive strength for a class of AAC masonry as specified in ASTM C 1386, psi (MPa). — [IBC 2009, Masonry](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/masonry.md) > For ordinary reinforced AAC masonry shear walls used in the seismic-foree-resisting system of structures, the response modification factor, R, shall be permitted to be taken as 2, the deflection amplification factor, Cd' shall be permitted to be taken as 2 and the system overstrength factor, Ωo, shall be permitted to be taken as 2½, Ordinary reinforced AAC masonry shear walls … — [IBC 2009, Structural Design](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/structural-design.md) ## The terms AAC masonry is built out of The definition above leans on 2 other defined terms. Each carries its own code definition, and a local amendment to any of them changes what AAC masonry covers: - **[Masonry](https://harth.build/resources/glossary/masonry.md)** — IBC 2009: A built-up construction or combination of building units or materials of clay, shale, concrete, glass, gypsum, stone or other approved units bonded together with or without mortar or grout or other accepted methods of joining. - **[Mortar](https://harth.build/resources/glossary/mortar.md)** — IBC 2009: A plastic mixture of approved cementitious materials, fine aggregates and water used to bond masonry or other structural units. ## AAC Masonry: 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 | Masonry | | | Re-check the requirement that uses it | Masonry (IBC 2009) | | | Re-check the requirement that uses it | Structural Design (IBC 2009) | | | Re-check the requirement that uses it | Definitions (IBC 2009) | | | Confirm the dependent definition | Masonry | | | Confirm the dependent definition | Mortar | | | 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) - [Masonry: Building Code Definition](https://harth.build/resources/glossary/masonry.md) - [Mortar: Building Code Definition](https://harth.build/resources/glossary/mortar.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 aac masonry? The International Building Code (IBC) 2009 defines it in Masonry as: “Masonry made of autoclaved aerated concrete (AAC) units, manufactured without internal reinforcement and bonded together using thin- or thick-bed mortar.” 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 aac masonry? In this corpus the term is used across 3 chapters, led by Masonry 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. --- - Continue in Harth (open this topic in the Harth agent): https://app.harth.build/agent?context=%2Fresources%2Fglossary%2Faac-masonry%2F - View this page in a browser: https://harth.build/resources/glossary/aac-masonry/ - All resources for agents: https://harth.build/llms.txt