Codes adopted by the City of Galveston
| Area | Code |
|---|---|
| Residential (1–2 family) | 2021 International Residential Code (IRC) |
| Commercial | 2021 International Building Code with local amendments |
| Mechanical, plumbing, fuel gas, pool & spa, energy | 2021 IMC, IPC, IFGC, ISPSC, IECC |
| Electrical | 2023 National Electrical Code |
| Land use | 2015 Land Development Regulations |
| Floodplain | Flood Damage Prevention Ordinance (Ord. 18-032, ch. 10 art. VIII) |
City of Galveston Building Division: (409) 797-3660 · galvestontx.gov building codes & permitting.
TDI windstorm code — applies countywide
On top of local codes, every building in Galveston County that wants TWIA coverage must meet the Texas Department of Insurance windstorm building code and receive a WPI-8 certificate. For projects with a WPI-1 filed on or after April 1, 2026, TDI uses the 2024 IRC / 2024 IBC with Texas revisions. Unincorporated Galveston County has limited code authority of its own, so the TDI windstorm code and county floodplain permitting are the main rules outside city limits.
Design wind speeds
TDI once mapped the coast into named zones. Galveston Island sat in the Seaward zone, the strictest.
Ultimate design wind speeds (ASCE 7-10 equivalents of the former 110 / 120 / 130 mph zones). Since the 2018 code update, designers use the ASCE 7 hazard tool for each specific site instead of named zones. Source: TDI Windstorm newsletter, 2018.
Roofing requirements
- Shingle class: where the allowable-stress design wind speed exceeds 100 mph — the whole Galveston area — asphalt shingles must be ASTM D7158 Class H or ASTM D3161 Class F (IRC Table R905.2.4.1).
- Fastening: at least 4 fasteners per shingle, or the manufacturer's high-wind instructions — commonly 6 nails on the coast.
- Underlayment: where ultimate design wind speed is 140 mph or more, the IRC requires high-wind underlayment details (two layers of felt or self-adhered membrane / taped seams).
- Reroofing: IRC R908 limits recovering over existing roofs — with two or more layers, tear-off to the deck is required.
- Permits & inspections: a roof replacement in the City of Galveston needs a city permit plus TDI windstorm inspection for the WPI-8.
Floodplain and elevation rules
- New or substantially improved homes: lowest floor at least 18 inches above Base Flood Elevation (BFE).
- Nonresidential: elevated or floodproofed to at least 18 inches above BFE.
- Substantial damage / improvement: when repair cost is 50% or more of the structure's pre-damage market value, the whole building must be brought into compliance — often meaning elevation.
On the island, BFEs commonly run from about 11 to more than 15 feet. If your home is declared substantially damaged, ask about Increased Cost of Compliance (ICC) coverage under your NFIP flood policy, which can help pay to elevate or demolish.
Not a Texas rule: the "25% roof rule"
You may hear that if 25% of a roof is damaged the whole roof must be replaced. That is a Florida building code provision, not Texas or Galveston law. In Galveston, full replacement arguments rest on matching, repairability, windstorm-code compliance and the actual extent of damage — which is exactly what we document.
General information as of September 2026; confirm current requirements with the City of Galveston Building Division and TDI before starting work.