Design Information

The County's Minimum Elevation is 1,000 feet and the Maximum Elevation is 14,152 feet.  The following design elements must be considered for all projects in Siskiyou County.

1. Requirement that California Design Professional seal and sign plans - A Case Study has established that the required flat roof snow loading (Pf) throughout Siskiyou County be of either 40 psf. or 60 psf.  
   • The snow loading listed in the California Building Code (when converted to Pg) exceeds the 50 psf listed under Section 2308.2.3 - Allowable loads, of the Conventional Light-Frame Construction Section of the Code. Therefore, Conventional Light-Frame Construction cannot be used in Siskiyou County. All structural plans and details must be submitted with California Licensed Professional seals & signatures. Buildings must be designed with psf flat roof snow load, with no reductions for slope are allowed. An equivalent ground snow loading  of (40 psf = 54 psf, 60 psf = 73 psf) may be used to calculate roof loads with no reductions for slope.  ​​​​​​​
2. Roof design loads for site above 5,000 feet elevation -  Must be obtained from the Building Division.
3. Flat roof snow load below 5,000 feet elevations -  McCloud, Mt. Shasta, Dunsmuir, Weed and Happy Camp, 60 pounds per square foot.  All Other areas, 40 pounds per square foot.  See the Roof Snow Load Bulletin webpage.
4. Basic Wind Speed, V, - The basic, general wind speed design loading for Siskiyou County is - 95 mph V, Risk Category II, Exposure C, for most structures below 5000 feet as a minimum requirement.
   • Minimum design wind loads are based upon the 2022 CBC, Sections 1604.A Wind Loads, 1609A.3 Basic design wind speed, 1609A.4.3 Exposure categories, and Figure 1609A.3(1) Basic Design Wind Speeds V map for Risk Category II Buildings and other structures and Chapter 26 Wind Loads ASCE/SEI 7-16. 
   • ASCE 7-10 defines the term V as the basic wind speed corresponding to a 3-sec gust speed at 33 ft. above the ground in Exposure Category C.    
5. Earthquake - the Seismic Design Category is determined by the Design Professional.
6. Soils Site Class - Based on soils investigation
7. Climate Zone 16 - for Energy compliance
8. Frost Depth -  12 inch minimum