Building Code Glossary
Basic Wind Speed: Building Code Definition
How the IRC 2009 define basic wind speed, 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
Basic wind speed is a defined term in the International Residential Code (IRC) 2009, in Definitions. The code's own words are: “Three-second gust speed at 33 feet (10 058 mm) above the ground in Exposure C (see Section R301.2.1) as given in Figure R301.2(4).” No other I-Code in this corpus defines it, so the IRC 2009 definition is the one to work from. The term is used in 11 chapters of this corpus, most often in Structural Design (IBC 2009), Building Planning (IRC 2009), Wall Construction (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?
Basic Wind Speed — IRC 2009, Definitions:
Three-second gust speed at 33 feet (10 058 mm) above the ground in Exposure C (see Section R301.2.1) as given in Figure R301.2(4).
What must be verified before using this guidance?
Basic Wind Speed is defined once in this corpus, in the Definitions chapter of the International Residential Code (IRC) 2009:
Three-second gust speed at 33 feet (10 058 mm) above the ground in Exposure C (see Section R301.2.1) as given in Figure R301.2(4).
Where basic wind speed is used in the code
The term appears in 11 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.
| Chapter | Code | Mentions |
|---|---|---|
| Structural Design | IBC 2009 | 27 |
| Building Planning | IRC 2009 | 19 |
| Wall Construction | IRC 2009 | 15 |
| Wall Covering | IRC 2009 | 13 |
| Roof Assemblies and Rooftop Structures | IBC 2009 | 7 |
| Structural Tests and Special Inspections | IBC 2009 | 5 |
| Wood | IBC 2009 | 4 |
| Definitions | IRC 2009 | 4 |
| Roof Assemblies | IRC 2009 | 3 |
| Exterior Walls | IBC 2009 | 2 |
| Foundations | IRC 2009 | 2 |
The term in use
How the code actually writes about basic wind speed, quoted from the 2009 text hosted here:
The type of opening protection required, the basic wind speed and the exposure category for a site is permitted to be determined in accordance with Section 1609 or ASCE 7.
The site-appropriate basic wind speed and exposure category shall be used in Tables R611.7(lA) through (lC) to determine the unreduced total length, UR, of solid wall required in each exterior endwallline and sidewall line.
Where the basic wind speed per Figure R301.2 (4) is 110 miles per hour (49 m/s) or higher, the attachment of wall coverings shall be designed to resist the component and cladding loads specified in Table R301.2 (2), adjusted for height and exposure in accordance with Table R301.2(3).
Basic Wind Speed: 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 IRC | Definitions | |
| Re-check the requirement that uses it | Structural Design (IBC 2009) | |
| Re-check the requirement that uses it | Building Planning (IRC 2009) | |
| Re-check the requirement that uses it | Wall Construction (IRC 2009) | |
| Re-check the requirement that uses it | Wall Covering (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
- Building: Building Code Definition
- Construction Documents: Building Code Definition
- Registered Design Professional: Building Code Definition
- Dwelling Unit: 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 basic wind speed?
The International Residential Code (IRC) 2009 defines it in Definitions as: “Three-second gust speed at 33 feet (10 058 mm) above the ground in Exposure C (see Section R301.2.1) as given in Figure R301.2(4).” 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 basic wind speed?
In this corpus the term is used across 11 chapters, led by Structural Design 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 basic wind speed?
In the 2009 I-Codes hosted here it is a defined term rather than a description. The IRC 2009 states, in Definitions: “Three-second gust speed at 33 feet (10 058 mm) above the ground in Exposure C (see Section R301.2.1) as given in Figure R301.2(4).” It is defined in IRC 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
- Base Flood: Building Code Definition
Base Flood — IBC 2009 definition: The flood having a I-percent chance of being equaled or exceeded in any given year.
- Basement Wall: Building Code Definition
Basement Wall — IRC 2009 definition: The opaque portion of a wall that encloses one side of a basement and has an …
- Basement: Building Code Definition
Basement — IBC 2009 definition: A story that is not a storyabovegrade plane (see "Story above grade plane" in Section 202).
- Bathroom Group: Building Code Definition
Bathroom Group — IRC 2009 definition: A group of fixtures, including or excluding a bidet, consisting of a water closet, lavatory, and …
- Bathroom: Building Code Definition
Bathroom — IRC 2009 definition: An area, including a basin, with one or more of the following: a toilet, a tub …
- Bed Joint: Building Code Definition
Bed Joint — IBC 2009 definition: The horizontal layer of mortar on which a masonry unit is laid.