Building Code Glossary
Gypsum Plaster: Building Code Definition
How the IBC 2009 define gypsum plaster, 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
Gypsum plaster is a defined term in the International Building Code (IBC) 2009, in Gypsum Board and Plaster. The code's own words are: “A mixture of calcined gypsum or calcined gypsum and lime and aggregate and other approved materials as specified in this code.” 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 4 chapters of this corpus, most often in Gypsum Board and Plaster (IBC 2009), Fire and Smoke Protection Features (IBC 2009), Wall Covering (IRC 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, Harth founder and architectural technology specialist · Published 2026-09-07 · Updated 2026-09-07.
What does this term mean?
Gypsum Plaster — IBC 2009, Gypsum Board and Plaster:
A mixture of calcined gypsum or calcined gypsum and lime and aggregate and other approved materials as specified in this code.
What must be verified before using this guidance?
Gypsum Plaster is defined once in this corpus, in the Gypsum Board and Plaster chapter of the International Building Code (IBC) 2009:
A mixture of calcined gypsum or calcined gypsum and lime and aggregate and other approved materials as specified in this code.
Where gypsum plaster is used in the code
The term appears in 4 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.
| Chapter | Code | Mentions |
|---|---|---|
| Gypsum Board and Plaster | IBC 2009 | 17 |
| Fire and Smoke Protection Features | IBC 2009 | 5 |
| Wall Covering | IRC 2009 | 4 |
| Definitions | IBC 2009 | 1 |
The term in use
How the code actually writes about gypsum plaster, quoted from the 2009 text hosted here:
Provisions of this chapter shall govern the materials, design, construction and quality of gypsum board, lath, gypsum plaster and cement plaster.
The minimum thickness of gypsum plaster or portland cement plaster used in a fire-resistance-rated system shall be determined by the prescribed fire tests.
Gypsum plaster materials shall conform to ASTM C 5, C 28, C 35, C 37, C 59, C 61, C 587, C 588, C 631, C 847, C 933, C 1032 and C 1047, and shall be installed or applied in conformance with ASTM C 843 and C 844.
Gypsum Plaster compared with Cement Plaster
These two are the closest pair in the 2009 I-Codes: about 65 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 | |
|---|---|
| Gypsum Plaster (IBC 2009) | calcined, gypsum |
| Cement Plaster (IBC 2009) | portland, blended, cement, hydrated, masonry, plastic |
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 gypsum plaster and cement plaster.
The terms gypsum plaster 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 gypsum plaster covers:
- Aggregate — IBC 2009: In roofing, crushed stone, crushed slag or water-worn gravel used for surfacing for roof coverings.
- Approved — IBC 2009: Acceptable to the code official or authority having jurisdiction.
Gypsum Plaster: 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 | Gypsum Board and Plaster | |
| Re-check the requirement that uses it | Gypsum Board and Plaster (IBC 2009) | |
| Re-check the requirement that uses it | Fire and Smoke Protection Features (IBC 2009) | |
| Re-check the requirement that uses it | Wall Covering (IRC 2009) | |
| Re-check the requirement that uses it | Definitions (IBC 2009) | |
| Confirm the dependent definition | Aggregate | |
| Confirm the dependent definition | Approved | |
| 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
- Aggregate: Building Code Definition
- Approved: 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 gypsum plaster?
The International Building Code (IBC) 2009 defines it in Gypsum Board and Plaster as: “A mixture of calcined gypsum or calcined gypsum and lime and aggregate and other approved materials as specified in this code.” 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 gypsum plaster?
In this corpus the term is used across 4 chapters, led by Gypsum Board and Plaster 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 are the specifications of gypsum plaster?
In the 2009 I-Codes hosted here it is a defined term rather than a description. The IBC 2009 states, in Gypsum Board and Plaster: “A mixture of calcined gypsum or calcined gypsum and lime and aggregate and other approved materials as specified in this code.” 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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