Updated 2026-09-07

Building Code Glossary

Site Class: Building Code Definition

How the IBC 2009 define site class, where the wording differs, and which chapters depend on the term.

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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.

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Direct answer

Site class is a defined term in the International Building Code (IBC) 2009, in Structural Design. The code's own words are: “A classification assigned to a site based on the types of soils present and their engineering properties as defined in Section 1613.5.2.” 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 Structural Design (IBC 2009), Soils and Foundations (IBC 2009), Building Planning (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?

Site Class — IBC 2009, Structural Design:

A classification assigned to a site based on the types of soils present and their engineering properties as defined in Section 1613.5.2.

Labeled code-term definition diagram: Site Class: Building Code Definition — How the IBC 2009 define site class, where the wording differs, and which chapters depend on the term.

What must be verified before using this guidance?

Site Class is defined once in this corpus, in the Structural Design chapter of the International Building Code (IBC) 2009:

A classification assigned to a site based on the types of soils present and their engineering properties as defined in Section 1613.5.2.

Where site class 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
Structural Design	IBC 2009	64
Soils and Foundations	IBC 2009	28
Building Planning	IRC 2009	13
Definitions	IBC 2009	1

The term in use

How the code actually writes about site class, quoted from the 2009 text hosted here:

Based on the site soil properties, the site shall be classified as either Site Class A, B, C, D, E or F in accordance with Table 1613.5.2.

— IBC 2009 §1613.5.2

Where a structure is assigned to Seismic Design Category D, E or F in accordance with Section 1613, individual spread footings founded on soil defined in Section 1613.5.2 as Site Class E or F shall be interconnected by ties.

— IBC 2009 §1809.13

The Seismic Design Categories and corresponding Short Period Design Spectral Response Accelerations, SDS shown in Figure R301.2(2) are based on soil Site Class D, as defined in Section 1613.5.2 of the International BUilding Code.

— IRC 2009 §R301.2.2.1.1

Site Class: 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	Structural Design (IBC 2009)
Re-check the requirement that uses it	Soils and Foundations (IBC 2009)
Re-check the requirement that uses it	Building Planning (IRC 2009)
Re-check the requirement that uses it	Definitions (IBC 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.

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 site class?

The International Building Code (IBC) 2009 defines it in Structural Design as: “A classification assigned to a site based on the types of soils present and their engineering properties as defined in Section 1613.5.2.” 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 site class?

In this corpus the term is used across 4 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 site class D?

In the 2009 I-Codes hosted here it is a defined term rather than a description. The IBC 2009 states, in Structural Design: “A classification assigned to a site based on the types of soils present and their engineering properties as defined in Section 1613.5.2.” 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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