San Francisco County, CA | 100-115 mph Design Wind Speed | CBC + SF Amendments | Golden Gate Winds | Seismic Dominates | Exposure B/C/D
Calculate San Francisco Wind Loads Now →San Francisco, as a consolidated city-county in California, has unique wind load requirements influenced by its coastal location, complex topography, and the famous Golden Gate wind corridor. The city adopts the California Building Code (CBC) with specific San Francisco amendments administered by the SF Department of Building Inspection. Design wind speeds for Risk Category II structures typically range from 100-115 mph (3-second gust) based on ASCE 7-22, though these values vary significantly with location and exposure.
Unlike most other jurisdictions, wind loads in San Francisco are typically NOT the governing design criteria—seismic design requirements almost always dominate due to the city's location on multiple active earthquake faults (San Andreas, Hayward). However, wind load analysis is still mandatory for code compliance, particularly for tall buildings, exposed coastal structures, and buildings near the Golden Gate Bridge wind corridor.
Design Wind Speed (Risk Category II): 100-115 mph (3-second gust, varies by location)
Design Wind Speed (Risk Category III): ~115-130 mph
Design Wind Speed (Risk Category IV): ~125-140 mph
Exposure Category: B (urban), C (waterfront/bay), D (exposed coastal)
Building Code: California Building Code (CBC) with SF Building Code amendments
Wind Load Standard: ASCE 7-22
County: San Francisco County (city-county)
Dominant Load: Seismic (wind typically does not govern)
San Francisco's design wind speed of 100-115 mph for Risk Category II structures reflects the city's Pacific Coast location and exposure to ocean winds. While these values are moderate compared to Gulf Coast or Atlantic hurricane regions, San Francisco faces unique wind challenges:
Despite moderate base wind speeds, San Francisco engineers must carefully evaluate exposure conditions, topographic effects, and local wind patterns—particularly for tall buildings and structures in exposed locations.
Calculating wind loads for San Francisco projects requires following ASCE 7-22 methodology as adopted by the CBC and SF amendments. The fundamental velocity pressure equation is:
qz = 0.00256 Kz Kzt Kd Ke V²
For San Francisco with V = 110 mph (typical) and standard conditions, the resulting pressures are moderate. A San Francisco project with:
Results in a velocity pressure of approximately qz = 29.3 psf—significantly lower than hurricane-prone regions but with critical topographic adjustments unique to San Francisco's hilly terrain.
For waterfront areas along San Francisco Bay using Exposure C, and exposed coastal areas using Exposure D, the pressures increase substantially due to higher velocity pressure coefficients and potentially higher base wind speeds.
California has a mandatory statewide building code—the California Building Code (CBC)—which is based on the International Building Code (IBC) with California-specific amendments. San Francisco further amends the CBC with local provisions:
Key San Francisco building code considerations:
You can access San Francisco building permits and requirements through the San Francisco Department of Building Inspection.
San Francisco 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 | San Francisco Design Wind Speed | Building Types |
|---|---|---|
| Risk Category I | ~95-105 mph | Agricultural facilities, temporary structures, minor storage |
| Risk Category II | 100-115 mph | Residential, commercial, most standard occupancies |
| Risk Category III | ~115-130 mph | Schools, assembly >300, substantial hazardous materials |
| Risk Category IV | ~125-140 mph | Hospitals, fire stations, emergency shelters, EOCs |
San Francisco projects require extremely careful Exposure Category determination due to the city's varied terrain and waterfront locations:
Exposure Category B (Urban/Downtown): Most of central and eastern San Francisco qualifies as Exposure B due to dense urban development with buildings, hills, and obstructions. Downtown, Financial District, Mission, Castro, and eastern 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 (Waterfront/Bay): Areas along San Francisco Bay, the Embarcadero, waterfront districts, and areas near the bay shoreline should use Exposure C. This includes open terrain with scattered obstructions having heights generally less than 30 feet. Exposure C produces significantly higher wind pressures than Exposure B.
Exposure Category D (Exposed Coastal): Western coastal areas facing the Pacific Ocean, particularly near Ocean Beach, Lands End, and the Presidio shoreline, may require Exposure D. This is the most conservative exposure category with the highest wind pressures, applicable to flat, unobstructed areas exposed to wind flowing over open water for distances greater than 1 mile.
Engineering Judgment Required: San Francisco's complex topography and microclimates require careful professional engineering judgment. The Golden Gate wind corridor, steep hills, and variable urban density create unique conditions. When in doubt, use the more conservative exposure category.
San Francisco's wind load analysis must account for unique local phenomena:
Golden Gate Wind Corridor: Prevailing westerly winds from the Pacific Ocean are funneled and accelerated through the narrow Golden Gate strait. This creates locally intense wind conditions in western neighborhoods including the Sunset District, Richmond District, and areas near the Presidio. Structures in these areas may experience significantly higher wind pressures than the base wind speed would suggest.
Topographic Effects (Kzt): San Francisco's famous steep hills require topographic factor adjustments per ASCE 7-22 Section 26.8. Buildings on hilltops, ridges, or escarpments can experience wind speed-up effects requiring Kzt values exceeding 1.0. Notable hills requiring topographic analysis include Twin Peaks, Telegraph Hill, Nob Hill, Russian Hill, and Pacific Heights.
Fog Considerations: While not directly a wind load issue, San Francisco's famous fog interacts with wind patterns and can affect cladding durability, corrosion protection requirements, and moisture management in building envelopes.
A critical consideration for San Francisco projects is that seismic design almost always governs over wind design:
San Francisco zip codes span diverse terrain with varying wind speed and exposure requirements:
The WindLoadCalc.com wind load calculator automatically applies the appropriate San Francisco wind speed based on your specific zip code or street address, accounting for proximity to the bay, ocean exposure, and local terrain conditions.
Wind load calculations for San Francisco building permits have strict PE requirements:
Engineers, architects, and contractors should reference these official resources for San Francisco wind load compliance:
The wind load calculator at WindLoadCalc.com automatically applies all San Francisco-specific requirements:
WindLoadCalc.com automatically handles all San Francisco-specific requirements including the 100-115 mph design velocity, appropriate Exposure Category selection (B/C/D), topographic effects for hills, Risk Category adjustments, and component pressure coefficients. Simply enter your San Francisco project address or zip code for instant, accurate calculations.
Calculate San Francisco Wind Loads Now →San Francisco's wind load requirements differ from other California coastal locations:
| Requirement | San Francisco | Southern CA Coast |
|---|---|---|
| Design Wind Speed | 100-115 mph | 85-100 mph (typically lower) |
| Exposure Category | B/C/D (highly variable) | B/C (typically less variable) |
| Topographic Effects | Critical (steep hills) | Moderate (gentler terrain) |
| Wind Patterns | Golden Gate corridor, microclimates | More uniform coastal winds |
| Dominant Load | Seismic (high seismicity) | Seismic (high seismicity) |
| Building Code | CBC + SF amendments | CBC + local amendments |
San Francisco's unique combination of coastal exposure, complex topography, Golden Gate wind effects, and extreme seismic requirements creates one of the most challenging building environments in the United States.
San Francisco has significant high-rise construction, particularly in the Financial District and South of Market (SOMA). Tall buildings require special wind considerations:
While not strictly wind load issues, San Francisco's coastal fog interacts with wind-driven moisture:
WindLoadCalc.com provides instant, accurate wind load calculations for San Francisco projects. Our software automatically handles the 100-115 mph velocity range, Exposure B/C/D determination, topographic effects, and generates PE-ready reports for SF DBI permit submission.
Try San Francisco Wind Load Calculator →