Design Criteria

General Design & Code Information

One and Two Family dwellings are governed by the 2017 Oregon Residential Specialty Code (ORSC) and all other structures are governed by the 2014 Oregon Structural Specialty Code (OSSC). Within this website, editorial changes have been made to actual Code language for the purpose of providing a more brief and readable document. In addition, the 2010 edition of the Oregon Manufactured Dwelling and Park Specialty Code is the primary code that addresses the installation and placement of Manufactured Dwelling units.

Basic Design Criteria

The following information is a listing of the basic design criteria required for all construction projects governed by the current edition of the Oregon Residential Specialty Code, and the Oregon Structural Specialty Code. More information at Oregon Snow Loading and Hazards by Location.

  • Concrete damage due to weathering: Moderate
  • Damage due to decay: Moderate
  • Damage due to insect infestation (termites): Moderate
  • Flood Hazards: The Douglas County Planning Department is responsible for locating 'floodways' and 'flood plains' in Douglas County. Consult the Planning office of the cities and towns in the county for Flood Hazard information within the cities or town's corporate boundaries.
  • Frost Depth: 12 inches below finished grade to bottom of footing at elevations of 2500 feet or below, above 2500 feet consult the Douglas County Building Department.
  • ORSC Basic Wind Speed V3S: 100 miles per hour (mph) (exposure 'C'; based on a 3 second gust 33 feet above the ground)/ 105 mph in areas with full exposure to ocean winds (exposure 'D')
  • OSSC Ultimate Design Wind Speed VUTL: 120 mph, 135 mph full exposure to ocean.
  • Relative elevations of some cities or towns in Douglas County:
    • Canyonville - 1249 feet; Drain - 291 feet; Elkton - 148 feet; Glendale - 1418 feet;
    • Myrtle Creek - 640 feet; Oakland - 430 feet; Reedsport - 10 feet; Riddle - 706 feet;
    • Roseburg - 479 feet; Sutherlin - 518 feet; Winston - 534 feet; Yoncalla - 354 feet
  • Roof Snow Load: 25 per square foot (psf) below elevations of 1500 feet; above 1500 feet consult Table 301.2(1); note a, or contact the Douglas County Building Department.
  • Seismic Zone: D1; Zone: D2 in areas west of Range 10 west of the Willamette Meridian for Manufactured Dwellings and Commercial Structures and Residential.
  • Soil Load Bearing Values: Minimum assumed value for in-place 'medium to stiff' soil conditions is 1500 psf, or 1000 psf for 'soft' in place conditions unless as otherwise determined by soils tests or geotechnical evaluation as required by sections 401.4 and 401.4.1 (residential only). Consult the Oregon Structural Specialty Code for Commercial requirements.
  • Tsunami Inundation Zone (PDF): Single Family Dwellings and Light Commercial structures are exempt. For detailed information see the Tsunami Inundation Zone handout
  • Uniformly distributed Live Loads: 40 psf - dwelling floors and decks/ see Table 301.5 for other values (residential only)
  • Wind Exposure: Recommend that exposure 'C' will be the most comprehensive category to use for design purposes, although category 'D' will apply in some coastal areas. Consult the Section R301.2.1.4 of the code for more specific information.
  • Wind Pressure: 18 psf/28 psf in areas with full exposure to ocean winds