FLORIDA · MONROE COUNTY
Key West sits where the continent ends and the open water takes over
The southernmost city in the United States, ringed by the Atlantic and the Gulf with no terrain to slow the wind. Design speeds run 170-180 mph on Exposure D, the harshest classification in ASCE 7-22.
EXTREME EXPOSURE · NOT A STATUTORY HVHZ
Why the southernmost city carries near-top-of-map wind loads
Key West is not inside the statutory High-Velocity Hurricane Zone — that designation belongs only to Miami-Dade and Broward. Yet the Keys answer to some of the strictest local wind provisions in Florida, driven by geography rather than the HVHZ label.
Surrounded by open water
Atlantic to the east, the Gulf to the west — fetch runs for miles in every direction.
EXPOSURE DDirect hurricane corridor
The Keys sit squarely in the prime Atlantic track; major storms pass directly overhead.
170-180 MPHNo terrain to shield it
Low, flat island with no ridges, forest, or upwind structures — Kzt stays at flat-ground 1.0.
KZT 1.0Wind-borne debris region
Impact-rated glazing or tested shutters required on every opening across Monroe County.
IMPACT REQUIREDExposure D versus the milder categories — at 15 ft, V = 175 mph
Exposure D (Key West): Kz = 1.03 → qz ≈ 67 psf
Exposure C (typical mainland coastal): Kz = 0.85 → qz ≈ 55 psf
Exposure B (suburban, not permitted here): Kz = 0.57 → qz ≈ 37 psf
Open-water Exposure D raises velocity pressure about 21% over Exposure C and roughly 81% over Exposure B at the same height and speed.
ASCE 7-22 · VELOCITY PRESSURE
One worked equation, Key West inputs
The velocity pressure equation governs the load. Plug in the island's mandatory Exposure D coefficient and a representative speed from the 170-180 mph band.
qz = 0.00256 · Kz · Kzt · Kd · Ke · V²
V = 175 mph — representative value inside the 170-180 mph Risk II band
Kz = 1.03 — 15 ft mean roof height, Exposure D
Kzt = 1.0 — flat island, no topographic feature
Kd = 0.85 — buildings (MWFRS & C&C)
Ke = 1.0 — sea-level elevation
Result: qz ≈ 67 psf — among the highest baseline velocity pressures for residential work anywhere in the country.
| Risk Category | Key West Design Speed | Typical Occupancy |
|---|---|---|
| I | ~155-165 mph | Agricultural, temporary, minor storage |
| II | 170-180 mph | Homes, retail, most standard occupancy |
| III | ~180-190 mph | Schools, assembly >300, substantial hazard |
| IV | ~190-200 mph | Hospitals, fire stations, shelters, EOCs |
Higher risk category means a longer return-period map and a higher speed — there is no fixed importance-factor multiplier in ASCE 7-22.
PERMIT-READY · MONROE COUNTY
What a compliant Key West submittal must carry
Every wind load package goes out under a Florida-licensed PE or architect seal, with these elements documented.
Exposure D justified
Open-water exposure stated and supported for the site.
Speed from the map
170-180 mph band, exact value read for the Risk Category.
Florida Product Approval
Statewide approval numbers for every exterior component.
Debris protection details
Impact glazing or tested shutters shown on every opening.
MWFRS & C&C pressures
Whole-frame and cladding pressures for all elements.
Sealed by a FL PE
Calculations under a Florida engineer or architect seal.
Common Keys missteps to design out
Defaulting to Exposure C
Open-water sites here demand Exposure D, not C.
"Not HVHZ, so relaxed"
The Keys aren't HVHZ but the loads run just as severe.
Unapproved products
Every exterior part needs a valid Florida approval number.
PROVEN BY STORMS · LOWER KEYS
The Keys have already taken the strongest hits on record
Hurricane Irma (2017) made Category 4 landfall at Cudjoe Key, just northeast of Key West — sustained 130 mph, gusts past 150 mph, hurricane-force winds for over twelve hours.
Buildings detailed to modern post-2002 FBC standards outperformed older stock — the case for designing to these extreme loads, made in the field.
FLORIDA KEYS · STATEWIDE CONTEXT
Where Key West fits in the Florida wind picture
The Lower Keys share this extreme exposure. Step out to the county, state, and national maps for the wider view.
Florida wind requirements
Statewide FBC and ASCE 7-22 wind rules, zone by zone.
STATEWIDEWind speed by location
Look up the design wind speed for any U.S. address.
LOOKUPAll state requirements
Browse adopted codes and wind provisions nationwide.
50 STATESLower Keys ZIP reference
33040
Key West — primary
ZIP33042
Summerland Key
ZIP33044
Cudjoe Key
ZIP33050
Marathon / Middle Keys
ZIPOfficial Monroe County & Florida resources
RUN THE NUMBERS
Calculate Key West loads with Exposure D built in
Enter a Lower Keys address and the calculator applies the 170-180 mph band, mandatory Exposure Category D, and full ASCE 7-22 methodology — producing PE-ready C&C and MWFRS output for Monroe County permits.