Appendix Q: 2018 IRC

Appendix Q: 2018 Residential Code

First Printing August 2017

Provisions Contained In This Appendix Are Not Mandatory Unless Specifically Referenced In The Adopting Reference

It Is Up To Each Municipality And State To Adopt  Appendix Q As A Model Code

Tiny Homes On A Foundation: 400 Square Feet Or Less

Written By Janet Thome

Appendix Q-Adopted  into  the 2018 International Residential Code ( IRC ) building code to provide regulations and standards for tiny homes on a foundation that is 400 square feet or less.

The International Residential Code is a comprehensive, stand alone residential code that creates minimum regulations for one-and two family dwellings of three stories or less.

The IRC brings together all building, plumbing, mechanical, fuel, gas, energy and electrical for provisions for one-and two-family residences.  Appendix Q was adopted to the IRC building code standards through the ICC Code Development Process.

ICC Code Development Process

Adoptions of the IRC

The International Residential Code (IRC) is in use or adopted in 49 states, the District of Columbia, Guam, Puerto Rico and the U.S. Virgin Islands. Wisconsin is the only state not applicable to IRC building codes. In Alaska the IRC is not adopted statewide. The “Deferred Cities” can adopt additional codes and some jurisdictions adopt the IRC and the IECC.

As a model code, the IRC is intended to be adopted in accordance with the laws and procedures of a governmental jurisdiction. When adopting a model code like the IRC, some jurisdictions amend the code in the process to reflect local practices and laws.


Appendix Q is applicable to tiny homes used as single dwelling units. Tiny homes shall comply with this code unless otherwise stated.

Appendix Q

From The ICC Learning Center 2018 IRC Update

ICC:  ANSI Standard Developer

ICC, the International Code Council, an ANSI Standard Developer ( ASD) is a nonprofit organization that develops and publishes standards related to building safety and fire prevention. Headquartered in Washington, D.C., United States, ICC standards have been codified and enforced in all 50 American states, as well as in various foreign countries. With nearly 340 chapters worldwide, each with many members, ICC building safety standards are used everywhere.

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