Spokane County, WA | 90-100 mph Design Wind Speed | WSBC (Adopts IBC) | Inland Northwest | Eastern Washington Hub | Exposure B/C
Calculate Spokane Wind Loads Now →Spokane, located in Spokane County, Washington, has unique wind load requirements influenced by its Inland Northwest location, proximity to the Rocky Mountains, and position as Eastern Washington's urban hub. The city adopts the Washington State Building Code (WSBC), which is based on the International Building Code (IBC) with Washington-specific amendments. Design wind speeds for Risk Category II structures typically range from 90-100 mph (3-second gust) based on ASCE 7-22, though these values vary with exposure and terrain.
As the largest city between Seattle and Minneapolis, Spokane experiences moderate wind conditions typical of inland regions. While wind loads are moderate, seismic design requirements are significant due to proximity to active fault systems. However, wind load analysis remains mandatory for code compliance, particularly for buildings in exposed areas and those in surrounding open terrain.
Design Wind Speed (Risk Category II): 90-100 mph (3-second gust)
Design Wind Speed (Risk Category III): ~105-115 mph
Design Wind Speed (Risk Category IV): ~115-125 mph
Exposure Category: B (urban), C (surrounding areas)
Building Code: Washington State Building Code (WSBC) - adopts IBC
Wind Load Standard: ASCE 7-22
County: Spokane County
Climate: Inland Northwest, four-season continental climate
Spokane's design wind speed of 90-100 mph for Risk Category II structures reflects the city's Inland Northwest location and moderate inland wind exposure. While these values are moderate compared to coastal regions, Spokane faces unique challenges:
Despite moderate base wind speeds, Spokane engineers must carefully evaluate exposure conditions, particularly for buildings in transitional zones between urban and open terrain.
Calculating wind loads for Spokane projects requires following ASCE 7-22 methodology as adopted by the WSBC. The fundamental velocity pressure equation is:
qz = 0.00256 Kz Kzt Kd Ke V²
For Spokane with V = 95 mph (typical) and standard conditions, the resulting pressures are moderate. A Spokane project with:
Results in a velocity pressure of approximately qz = 19.8 psf—moderate pressures typical of Inland Northwest urban locations.
For areas in surrounding open terrain using Exposure C, the pressures increase due to higher velocity pressure coefficients (Kz), potentially reaching 25+ psf at roof heights.
Washington has a mandatory statewide building code—the Washington State Building Code (WSBC)—which is based on the International Building Code (IBC) with Washington-specific amendments:
Key Spokane building code considerations:
You can access Spokane building permits and requirements through the City of Spokane Building and Planning Services.
Spokane projects must be classified into Risk Categories per ASCE 7-22 Table 1.5-1. Higher risk categories require increased design wind speeds:
| Risk Category | Spokane Design Wind Speed | Building Types |
|---|---|---|
| Risk Category I | ~85-95 mph | Agricultural facilities, temporary structures, minor storage |
| Risk Category II | 90-100 mph | Residential, commercial, most standard occupancies |
| Risk Category III | ~105-115 mph | Schools, assembly >300, substantial hazardous materials |
| Risk Category IV | ~115-125 mph | Hospitals, fire stations, emergency shelters, EOCs |
Spokane projects require careful Exposure Category determination based on surrounding terrain and development density:
Exposure Category B (Urban): Most of downtown Spokane and established neighborhoods qualify as Exposure B due to dense urban development with buildings, houses, and mature trees. Downtown, Browne's Addition, South Hill, Logan, Hillyard, and most residential neighborhoods typically use Exposure B. This assumes urban areas with buildings having heights generally less than 30 feet extending more than 800 feet upwind.
Exposure Category C (Surrounding Areas): Areas outside the urban core, particularly in Spokane Valley, Liberty Lake, and surrounding agricultural or prairie lands should use Exposure C. This includes new developments at the urban fringe, industrial parks, and properties with open terrain exposure. Exposure C produces significantly higher wind pressures than Exposure B due to reduced surface roughness.
Engineering Judgment Required: Buildings in transitional zones between urban and open areas require professional engineering judgment. When in doubt, use the more conservative exposure category (C over B).
Spokane's wind load analysis must account for unique local conditions:
Spokane River Valley: The Spokane River cuts through downtown, creating the scenic Spokane Falls and Riverfront Park. Buildings along the river gorge may experience channeling effects and should be evaluated carefully for local wind acceleration.
South Hill Elevation: The South Hill neighborhood sits at higher elevation than downtown, potentially experiencing different wind conditions. Topographic effects should be evaluated for buildings on prominent hills.
Evergreen Forests: Surrounding ponderosa pine forests and evergreen vegetation provide natural wind protection in many areas, contributing to Exposure B conditions in wooded neighborhoods.
A critical consideration for Spokane projects is that seismic design often governs over wind design:
Spokane zip codes span diverse terrain with varying wind speed and exposure requirements:
The WindLoadCalc.com wind load calculator automatically applies the appropriate Spokane wind speed based on your specific zip code or street address, accounting for local terrain conditions and urban development patterns.
Wind load calculations for Spokane building permits have strict PE requirements:
Engineers, architects, and contractors should reference these official resources for Spokane wind load compliance:
The wind load calculator at WindLoadCalc.com automatically applies all Spokane-specific requirements:
WindLoadCalc.com automatically handles all Spokane-specific requirements including the 90-100 mph design velocity, appropriate Exposure Category selection (B/C), Risk Category adjustments, and component pressure coefficients. Simply enter your Spokane project address or zip code for instant, accurate calculations.
Calculate Spokane Wind Loads Now →Spokane's wind load requirements differ from Western Washington cities due to its inland location:
| Requirement | Spokane | Seattle, WA |
|---|---|---|
| Design Wind Speed | 90-100 mph | 100-110 mph |
| Exposure Category | B (urban), C (surrounding) | B (urban), C (waterfront) |
| Building Code | WSBC (adopts IBC) | WSBC (adopts IBC) |
| Location | Inland Northwest | Puget Sound waterfront |
| Seismic Concerns | Moderate to High | High (Cascadia, Seattle Fault) |
| Climate | Continental, four-season | Rainy maritime |
Spokane's unique position as Eastern Washington's largest city creates a distinctive building environment combining Inland Northwest terrain, moderate wind exposure, and continental climate requiring careful engineering analysis.
Spokane hosted the 1974 World's Fair (Expo '74), which transformed the downtown waterfront and created Riverfront Park. Wind analysis for this historic area requires special considerations:
Spokane is home to Gonzaga University and other educational institutions, which often require Risk Category III design:
Spokane receives significant snowfall, creating important interaction between snow and wind loads:
WindLoadCalc.com provides instant, accurate wind load calculations for Spokane projects. Our software automatically handles the 90-100 mph velocity range, Exposure B/C determination, and generates PE-ready reports for City of Spokane permit submission.
Try Spokane Wind Load Calculator →