Design Criteria and Current Codes

Seismic DesignOSSC 1613

  • Seismic Design Category – D

Wind DesignOSSC 1609
Wind Exposure is site specific and it is the design professional's responsibility to determine the exposure category selected for the area of construction.

Ultimate Design Wind Speed
Risk Category I 115 mph
Risk Category II 120 mph
Risk Category III or IV 130 mph

Soil Load-Bearing ValuesOSSC 1806
These presumptive design soil load-bearing values shall be used if a geotechnical report is unavailable for the project.

Class of Soil Material ML, Inorganic Silts and Clayey Silts
Vertical Foundation Pressure 1,500 psf
Coefficient of Friction 0.25

Soil Lateral LoadsOSSC 1610
These presumptive design soil lateral loads shall be used if a geotechnical report is unavailable for the project.

Active Pressure 45 psf
At-Rest Pressure 100 psf

Snow LoadsOSSC 1608

Foundation Frost ProtectionOSSC 1809.5

To protect foundations from frost, they must be installed below the determined frost depth.  The table below provides the minimum top of footing depth from grade based upon the elevation where the project is located.

Frost depth
Project site elevation Minimum frost depth to top of footing
Below 2,500 ft 12 inches
Above 2,500 ft 18 inches

Design criteria for residential structures

Seismic Design – ORSC Table R301.2(2)

  • Seismic Design Category – D1

Wind Design – ORSC Figure R301.2(4)

  • Basic Wind Speed – 93 mph

Soil Load-Bearing Values – ORSC Table 401.4.1
The design load-bearing values shall be used if a geotechnical report is unavailable for the project.

  • Class of Soil Material – ML, Inorganic Silts and Clayey Silts
  • Vertical Foundation Pressure – 1,500 psf

Snow LoadsOSSC 1608

Foundation Frost Protection – OSSC 1809.5

To protect foundations from frost, they must be installed below the determined frost depth.  The table below provides the minimum bottom of footing depth from grade based upon the elevation where the project is located.

Frost depth
Project site elevation Minimum frost depth to top of footing
Below 2,500 ft 12 inches
Above 2,500 ft 18 inches

Current Adopted Codes