Building Code Glossary
Design Flood: Building Code Definition
How the IBC 2009 define design flood, 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
Design flood is a defined term in the International Building Code (IBC) 2009, in Structural Design. The code's own words are: “The flood associated with the greater of the following two areas:” 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 21 chapters of this corpus, most often in Building Planning (IRC 2009), Structural Design (IBC 2009), General Regulations (IPC 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?
Design Flood — IBC 2009, Structural Design:
The flood associated with the greater of the following two areas:
What must be verified before using this guidance?
Design Flood is defined once in this corpus, in the Structural Design chapter of the International Building Code (IBC) 2009:
The flood associated with the greater of the following two areas:
Where design flood is used in the code
The term appears in 21 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.
| Chapter | Code | Mentions |
|---|---|---|
| Building Planning | IRC 2009 | 81 |
| Structural Design | IBC 2009 | 19 |
| General Regulations | IPC 2009 | 11 |
| Scope and Administration | IRC 2009 | 10 |
| Scope and Administration | IBC 2009 | 8 |
| Fuel Gas | IRC 2009 | 7 |
| Accessibility | IBC 2009 | 4 |
| Duct Systems | IMC 2009 | 4 |
| Fuel Oil Piping and Storage | IMC 2009 | 4 |
| Soils and Foundations | IBC 2009 | 3 |
| General Regulations | IMC 2009 | 3 |
| Site Evaluation and Requirements | IPC 2009 | 3 |
9 further chapters mention the term.
The term in use
How the code actually writes about design flood, quoted from the 2009 text hosted here:
All structural systems of all buildings and structures shall be designed, connected and anchored to resist flotation, collapse or permanent lateral movement due to structural loads and stresses from flooding equal to the design flood elevation.
In riverine flood hazard areas where design flood elevations are specified but floodways have not been designated, the applicant shall provide a floodway analysis that demonstrates that the proposed work will not increase the design flood elevation more than 1 foot (305 mm) at any point within the jurisdiction of the applicable governing authority.
The construction documents submitted with the application for permit shall be accompanied by a site plan showing to scale the size and location of new construction and existing structures on the site, distances from lot lines, the established street grades and the proposed finished grades and, as applicable, flood hazard areas, floodways, and design flood elevations;
Design Flood: 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 | Structural Design | |
| Re-check the requirement that uses it | Building Planning (IRC 2009) | |
| Re-check the requirement that uses it | Structural Design (IBC 2009) | |
| Re-check the requirement that uses it | General Regulations (IPC 2009) | |
| Re-check the requirement that uses it | Scope and Administration (IRC 2009) | |
| 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
- Design Flood Elevation: Building Code Definition
- Loads: Building Code Definition
- Seismic Design Category: Building Code Definition
- Mechanical Systems: 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 design flood?
The International Building Code (IBC) 2009 defines it in Structural Design as: “The flood associated with the greater of the following two areas:” 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 design flood?
In this corpus the term is used across 21 chapters, led by Building Planning in the IRC 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 the definition of design flood elevation?
In the 2009 I-Codes hosted here it is a defined term rather than a description. The IBC 2009 states, in Structural Design: “The flood associated with the greater of the following two areas:” 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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