TEXAS · GALVESTON
Galveston Island takes the full sweep of the Gulf
A barrier island fronting open water, Galveston carries some of the highest design wind speeds in Texas: 150-160 mph, Exposure D, and mandatory TWIA windstorm certification.
BARRIER ISLAND EXPOSURE
Why this island reads the highest map in Texas
Galveston Island sits in Galveston County as a low barrier island fronting the Gulf of Mexico, with Galveston Bay behind it. With water on both sides and no upwind terrain to slow the storm, the ASCE 7 maps place it at the top of the Texas wind range.
Open water, both sides
Gulf fetch ahead and Galveston Bay behind leave almost no terrain roughness to dissipate hurricane energy.
FULL GULF FETCHFlat, low, sea-level
A nearly flat island at sea level means Kzt stays at 1.0 - no sheltering hills, just unobstructed wind on the structure.
FLAT TERRAINA direct-strike coast
Hurricanes from 1900 to Carla, Alicia, and Ike have made Galveston a proven landfall corridor, not a sheltered bay.
LANDFALL CORRIDORDESIGN BASIS · ASCE 7-22
The Galveston design envelope
What an engineer pulls before sealing a set of Galveston barrier-island calculations.
Wind speed
150-160 mph (3-second gust) for Risk Category II - the high end of the Texas range.
150-160 MPHExposure D
Oceanfront and bay-facing sites read Exposure D for wind flowing in over open water.
OPEN WATERTWIA certification
Galveston County is a designated catastrophe area; a WPI-8 windstorm certificate is required for coverage.
WPI-8 REQUIREDCode & standard
International Building Code with Texas amendments, calculated per ASCE 7, plus TDI windstorm rules.
IBC + ASCE 7Exposure D vs. C on the island
Gulf-facing and beachfront lots definitively take Exposure D - the most severe category, where wind crosses open water for at least a mile upwind. Bay-side or more inland lots may qualify for Exposure C depending on fetch and terrain, but the seawall does not lower the design wind; structures still resist the full 150-160 mph.
ASCE 7-22 · TABLE 1.5-1
How risk category moves the Galveston map
Risk category does not multiply the wind speed - it sends you to a different return-period map. Higher category, longer return period, higher mph.
| Risk Category | Map (MRI) | Building types on the island |
|---|---|---|
| I | 300-year | Minor ag, storage, temporary structures (lowest map) |
| II | 700-year | Homes, retail, most standard occupancies - 150-160 mph |
| III | 1,700-year | Schools, assembly over 300, substantial-hazard occupancies |
| IV | 3,000-year | Hospitals, fire/police, EOCs, hurricane shelters (highest map) |
A COAST WRITTEN BY STORMS
The history behind the highest numbers
Galveston's wind requirements are not abstract - they were paid for in the worst hurricane disaster the country has recorded.
1900 · Category 4
The deadliest U.S. natural disaster; it spurred the Galveston Seawall and the island grade-raising.
DEADLIEST U.S.Carla · 1961 · Cat 4
175 mph winds and a 22-foot surge at Port Lavaca brought major damage across coastal Texas.
175 MPHAlicia · 1983 · Cat 3
A direct hit with 115 mph winds that exposed deficiencies in 1970s-era construction.
DIRECT HITIke · 2008 · Cat 2
Its huge size drove 110 mph winds and a 15-foot surge, destroying thousands of structures.
15-FT SURGEPERMIT & CERTIFICATION CHECKLIST
What it takes to build and insure here
Every Galveston set ties wind loads to a Texas-licensed PE seal and TWIA windstorm documentation.
Texas PE seal
Calculations sealed by a PE licensed in Texas; TWIA certification also requires PE-sealed documentation.
PE REQUIREDWind determination
Address-based ASCE 7 wind speed in the 150-160 mph range with the risk category documented.
150-160 MPHExposure call
Exposure D for oceanfront and bay-facing lots; Exposure C only where terrain and fetch support it.
D / CTWIA / WPI-8
Windstorm certification through the Texas Department of Insurance for coverage eligibility.
WINDSTORMC&C + MWFRS
Component and cladding pressures plus main-frame loads for windows, doors, roof, and walls.
FULL ENVELOPESurge & flood
Most of the island sits in high-risk flood zones; wind loads pair with FEMA flood and surge design.
COASTAL ZONEOFFICIAL GALVESTON & TEXAS RESOURCES
Where the authorities live
The jurisdictions and boards governing wind, windstorm, and engineering on the island.
City of Galveston
Local building permits enforcing IBC and TWIA standards.
VISITGalveston County
County authority across the designated coastal jurisdiction.
VISITTDI - TWIA
Texas Department of Insurance windstorm certification division.
VISITTexas Board of PEs
Licensing board for the engineers sealing Galveston sets.
VISITKEEP EXPLORING
From the island to the statewide picture
Galveston is one of the highest-wind sites in Texas - see how it fits the broader maps and codes.
Texas requirements
Statewide wind speeds, codes, and the coastal county framework.
STATEWIDEAll state requirements
Compare wind codes and ASCE 7 editions across every state.
50 STATESWind speed by location
Look up design wind speed for any U.S. address or zip.
LOOKUPHVHZ vs. standard zones
How Texas TWIA windstorm rules differ from Florida HVHZ.
COMPARERUN THE NUMBERS
Get Galveston-compliant wind loads in minutes
Enter a Galveston address and the calculator applies the 150-160 mph design velocity, Exposure D oceanfront conditions, risk category, and full ASCE 7 envelope - PE-ready for permits and TWIA certification.