Building Codes & Design Criteria

2021 Washington State Code Revised Effective Date

The State Building Code Council voted on September 15, 2023, to delay the effective date of the 2021 Washington State codes. The new code effective date will be March 15, 2024.  The previous effective date was October 29, 2023 and July 1, 2023 respectively.

Design Criteria

Cowlitz County Design Criteria 

The Washington State Building Code includes the 2018 International Building Code (IBC) and International Residential Code (IRC) as adopted pursuant to the Cowlitz County Code (CCC) Title 16. The following design criteria are applicable within the jurisdiction of Cowlitz County.


Ground snow load, Pg: Refer to CCC Section 16.05.070  Table A.

 FROST DEPTH: 12 inches


  • Winter Design Temperature: 22 F degrees.
  • Mean annual temperature: 51.5 F degrees.
  • Air Freezing Index: 170


Commercial structures, IBC Section 1609 –

  • Ultimate Design Wind Speed Vult: Figures 1609.3(1), 1609.3(2) and 1609.3(3).
  • Exposure Category shall be established by the designer in accordance with Section 1609 or ASCE 07.

Residential structures, IRC Section R301.2.1 –

  • Ultimate Design Wind Speed Vult: 110. IRC Figure R301.2(4)A.
  • Exposure Category shall be established by the designer in accordance with Section R301.2.1.4.


Commercial structures, IBC Section 1613 –

  • Seismic Design Category D. Site specific information may be obtained from the U.S. Seismic Design Maps developed by the United States Geologic Survey.

Residential structures, IRC Section R301.2.2 –

  • Seismic Design Category D1.


Flood Hazard construction shall comply with the provisions of CCC 16.25 "Flood Management".


Commercial structures, IBC Section 1803 -

Residential structures, IRC Sec R401.4 –

Unless determined otherwise by soil investigation, presumptive load-bearing value 1500 PSF.

Building Codes

Cowlitz County Code (CCC) 16.05, International Building Code (IBC), International Residential Code (IRC), International Mechanical Code (IMC), Uniform Plumbing Code (UPC), International Fire Code (IFC), and the Washington State Energy Code.  

The purpose of Codes Administration is to perform responsible oversight and enforcement of the State Building Code Act and County ordinances regulating building and construction. When applications for permits are submitted for review, plans are checked for conformance with the:

After permits are issued and work has begun, building inspectors perform inspections to assure compliance with all applicable codes.

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