Local Design Criteria

Residential Local Design Category Information:

  • Basic Design Wind Speed (ORSC Figure R301.2(4))
    • 135mph
    • Most areas in Warrenton are classified as wind exposure category B, however some areas fronting the Columbia River or other bodies of water may meet the criteria of category C & D.
  • Seismic Design Category (ORSC Figure R301.2(2))
    • D2
  • Snow Load (ORSC Table R301.2(1))
    • 25psf for elevations less than 400’
  • Soils Load-Bearing Pressure (ORSC Table R401.4.1)
    • 1500psi typical
  • Frost Line Depth (ORSC Table R301.2(1))
    • 12”
  • Wetlands & Hydric Soils
    • BE ADVISED; The City of Warrenton contains large areas of wetland and hydric soil. Where data indicates questionable soil characteristics are likely present the Building Official shall determine the requirement for a soils test via geotechnical evaluation (ORSC R401.4)
      • Wetland development is regulated by the U.S. Army Corp of Engineers and Oregon Department of State Lands.
      • Hydric Soils is soil which is permanently or seasonally saturated with water. This soil is not suitable for construction and requires mitigation including but not limited to; removal of excess waters, engineered fill, and engineered footings.
    • Wetlands and Soils maps established by Federal and State agencies (USDA & Oregon DSL) and available for reference at https://delta.co.clatsop.or.us/apps/ClatsopCounty/index.html

Commercial Local Design Category Information:

  • Basic Design Wind Speed (OSSC Table 1609.3)
    • Risk Category I = 125 (Clatsop County special wind region)
    • Risk Category II = 135 (Clatsop County special wind region)
    • Risk Category III = 145(Clatsop County special wind region)
    • Risk Category IV = 145 (Clatsop County special wind region)
    • Most areas in Warrenton are classified as wind exposure category B, however some areas fronting the Columbia River or other bodies of water may meet the criteria of category D.
  • Seismic Design Category
    • Most structures in Warrenton are assigned Seismic Design Category D in accordance with OSSC 1613.2.5. Seismic design parameters should be obtained from https://hazards.atcouncil.org/
    • Site Class D shall be used unless the Building Official or geotechnical report determines Site Class E or F soils are present at the site.
    • Seismic Coefficient is based upon soil type.
  • Soils
    • Geotechnical investigations shall be conducted in accordance with OSSC Section 1803.2 and reported in accordance with OSSC Section 1803.6.
    • Presumptive Load-Bearing Pressure in accordance with OSSC Table 1806.2
      • 1500psf (vertical foundation pressure)
      • 100psf/ft (lateral bearing pressure)
    • Wetlands & Hydric Soils
  • Flood Design Data
    • Flood Hazard Areas are established by the Federal Emergency Management Agency and available for reference at https://msc.fema.gov/portal/home
    • Design Flood Elevation shall be determined by Flood Hazard Areas map or by method approved by Building Official in accordance with OSSC 1612.3.1.
  • Rain Load Data
    • 1.3-inch/hour (OPSC Table D 101.1)
  • Snow Load
    • In accordance with OSSC 1608.2.2, the ground snow load is based on Snow Load Analysis for Oregon as published by the Structural Engineer Association of Oregon http://snowload.seao.org
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