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Seismic Design
- Seismic Design Category – D
Wind Design
OSSC 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.
| Basic Design Wind Speed | Special Wind Region* | |
| Risk Category I | 92 mph | 115 mph |
| Risk Category II | 98 mph | 120 mph |
| Risk Category III | 105 mph | 130 mph |
| Risk Category IV | 109 mph | 130 mph |
* Sites located within a special wind region shall be verified online.
Soil Load-Bearing Values
OSSC 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 Loads
OSSC 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 Loads
- Reference Clackamas County's snow load design criteria.
Foundation Frost Protection
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 Figure R301.2.2.1
Wind Design
ORSC Table R301.2(1)
- Basic Design Wind Speed – 98 mph
ORSC Table R301.2(1)
- Special Wind Region,
Basic Design Wind Speed - 120 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
- Reference Clackamas County's snow load design criteria
Foundation Frost Protection
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 |
