Design Criteria and Current Codes

Seismic Design

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  • Seismic Design Category – D

Wind Design

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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 Values

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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 Loads

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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 Loads

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Foundation Frost Protection

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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 bottom of footing
Below 2,500 ft 12 inches
2,500 to 4,000 ft 18 inches
Above 4,000 ft 24 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 Loads

OSSC 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 bottom of footing
Below 2,500 ft 12 inches
2,500 to 4,000 ft 18 inches
Above 4,000 ft 24 inches

Current Adopted Codes

Phone:503-742-4240
Fax:503-742-4741
Email:bldservice@clackamas.us

150 Beavercreek Road Oregon City, OR 97045

Office Hours:

Lobby Hours
Monday to Thursday: 8 a.m. to 4 p.m.
Friday: 8 a.m. to 3 p.m.
Inspections: Monday to Friday

Inspection Request Line:
503-742-4720

Soils/Septic Questions:
503-742-4740