WASHINGTON · PIERCE COUNTY / CITY OF TACOMA
Where Commencement Bay Meets the Code: Tacoma Wind Load Requirements
South Puget Sound's working port city designs to the Washington State Building Code and ASCE 7-22 — moderate winds, demanding waterfront exposure.
PACIFIC NORTHWEST WINDSTORMS · TIDEFLATS FETCH
Why a Port Town Reads Two Exposures at Once
Tacoma's basic wind speed is moderate, but the open water of Commencement Bay and the flat Tideflats stretch Exposure C right up against an Exposure B downtown.
Off-the-Sound Gusts
Pacific NW frontal windstorms drive sustained, rain-laden gusts across the bay — the envelope, not the frame, often takes the worst of it.
95-110 MPHDowntown & North End = B
Dense blocks across Stadium, Proctor, Hilltop and the North End give upwind roughness — most inland sites qualify as Exposure B.
EXPOSURE BTideflats & Port = C
Ruston Way, Point Defiance shoreline and the Port of Tacoma container yards carry open-fetch Exposure C and the highest pressures in the city.
EXPOSURE CIn the transition between bay-front industry and sheltered hillside neighborhoods, judgment governs. ASCE 7-22 §26.7 sets the rule; when a site straddles both, the more conservative Exposure C is the safe call.
WSBC PERMIT PATH · CITY OF TACOMA
What It Takes to Clear Pierce County Review
Every Tacoma structural submittal carries the same backbone — set the speed, set the exposure, prove the load case that governs.
Lock the Basic Speed
Read V from the ASCE 7-22 Risk-category map — 95-110 mph for standard Risk II Tacoma sites; speed varies by site.
ASCE 7-22 MAPPin the Exposure
Decide B or C from the actual upwind terrain — waterfront and Tideflats sites trend C, sheltered hillsides trend B.
B / CRun MWFRS & C&C
Compute qz = 0.00256·Kz·Kzt·Kd·Ke·V², then pressures for the frame and every cladding zone with Kd = 0.85.
qz METHODStamp It WA-Licensed
A Washington-licensed PE seals the calc; City of Tacoma Development Services plan-checks before the permit issues.
PE SEALCoastal salt air and Cascadia seismic demand sit alongside wind — but wind almost always governs cladding, windows and roofing, even when seismic drives the frame.
ASCE 7-22 TABLE 1.5-1 · RETURN-PERIOD MAPS
Higher Stakes, a Longer-Return Map
Risk category doesn't multiply your load — it sends you to a different basic-speed map with a longer mean recurrence interval.
| Risk Category | Speed Map (MRI) | Typical Tacoma Occupancy |
|---|---|---|
| I | 300-yr (lowest) | Minor storage, ag and incidental Tideflats sheds |
| II | 700-yr (standard · 95-110 mph) | Homes, retail, offices, most port warehouses |
| III | 1,700-yr | Schools, assembly over 300, hazardous-material sites |
| IV | 3,000-yr | Hospitals, fire and police, EOCs, emergency shelters |
Move up a category and you read V from a higher-speed map — exact mph still varies by your Tacoma site.
PUGET SOUND CONTEXT · STATEWIDE WIND DATA
Compare Across the Washington Wind Map
See how Tacoma's Commencement Bay numbers sit beside its neighbors and the statewide picture.
Seattle
Elliott Bay neighbor with urban high-rise exposure.
100-110 MPHWashington Statewide
WSBC adoption and wind speeds across the whole state.
STATE GUIDEWind Speed by Location
Look up the basic wind speed for any U.S. address.
LOOKUPAll State Requirements
Adopted codes and ASCE editions, state by state.
50 STATESFROM TIDEFLATS TO HILLTOP · INSTANT NUMBERS
Calculate Tacoma Loads, Permit-Ready
Drop in a Commencement Bay address — the calculator sets the 95-110 mph speed, the right Exposure B or C, and builds a WA PE-ready ASCE 7-22 report.