# International Residential Code > The 2009 International Residential Code, incorporated by reference into the Washington State Building Code (WAC 51-51). Covers the design and construction of one- and two-family dwellings and townhouses. - Canonical: https://harth.build/resources/building-codes/us-states/washington/irc-2009/ - Last updated: 2026-06-23 ## Direct answer and reference scope International Residential Code is presented here as a reference within the IRC 2009 collection for Washington. The 2009 International Residential Code, incorporated by reference into the Washington State Building Code (WAC 51-51). Covers the design and construction of one- and two-family dwellings and townhouses. Use the [Washington State Building Code Council](https://sbcc.wa.gov/state-codes-regulations-guidelines) to confirm the code edition currently adopted for the project, and compare the model text with state amendments, local amendments, effective dates and the permit authority's interpretation. The [ICC code library](https://codes.iccsafe.org/codes) is the model-code publication path. This Harth page is a searchable reference transcription, not an official code publication, legal opinion or confirmation that this edition controls a particular address. Record the project jurisdiction, application date, occupancy, construction type and amendment set before relying on a section. Where this page conflicts with an official publication or the authority having jurisdiction, the official source controls. _Authored and prepared by Harth. Review scope: official verification path added; code text and current local applicability have not been independently reviewed._ Washington adopted the 2009 IRC as WAC 51-51, effective July 1, 2010, with state amendments (Washington does not adopt the IRC energy chapter, relying instead on its own State Energy Code). The full text below is reproduced from the 2009 edition as incorporated into law, sourced from public.resource.org, and covers building planning, structural, mechanical, and plumbing provisions for homes. --- - Continue in Harth (open this topic in the Harth agent): https://app.harth.build/?context=%2Fresources%2Fbuilding-codes%2Fus-states%2Fwashington%2Firc-2009%2F - View this page in a browser: https://harth.build/resources/building-codes/us-states/washington/irc-2009/ - All resources for agents: https://harth.build/llms.txt