TEXAS · DALLAS
Where the North Texas plains meet Tornado Alley wind design
Dallas County sits far inland from the Gulf, but on the southern flank of Tornado Alley its severe-storm climate sets the design wind speed. Here is what ASCE 7-22 asks of every Dallas roof, wall, and frame.
NORTH TEXAS CLIMATE
An inland metro shaped by convective, not coastal, wind
Roughly 250 miles from the Gulf, Dallas never sees hurricane design loads. Its 105–115 mph map value is driven instead by spring and summer storm season across the DFW prairie.
Straight-line storm winds
Derecho-style squall lines push damaging gusts across the open metroplex each storm season.
CONVECTIVETornado Alley's southern edge
Dallas County logs multiple tornadoes a year, a hazard the elevated base wind speed reflects.
SEVEREHail belt roof demand
One of the nation's most hail-struck cities; roofs resist uplift and impact together.
ROOF SYSTEMSNo coastal certification
Far from TWIA's 14 coastal counties: no wind-borne debris or windstorm certificate applies.
INLANDASCE 7-22 tornado note: The 2022 edition added Chapter 32 tornado-load provisions for higher risk categories. For most standard Dallas occupancies, design is still governed by the synoptic basic wind speed map; the tornado climate is what keeps that mapped value in the 105–115 mph band rather than lower inland numbers.
TERRAIN CALL
Reading exposure across a fast-spreading prairie metro
Dallas straddles two terrain pictures: built-up neighborhoods and raw, expanding suburban edge. Picking the wrong one changes every pressure on the page.
Exposure B — established Dallas fabric
Downtown, Uptown, the Park Cities and mature suburbs sit inside dense, sheltering build-out. The default for most permits inside Loop development.
URBAN / SUBURBANExposure C — the open northern edge
New tracts on the far-north prairie can still read as open terrain mid-build, lifting pressures well above the sheltered case until surroundings fill in.
OPEN TERRAINWhere the line moves: Dallas's rapidly developing northern fringe makes the B-to-C boundary a judgment call. When upwind build-out is incomplete, the more conservative Exposure C governs until the terrain matures.
RISK & RETURN PERIOD
How occupancy raises Dallas's mapped wind speed
ASCE 7-22 has no wind importance factor. A higher risk category instead reads a longer-return-period map, so essential Dallas facilities design to a higher gust than homes do.
| Risk Category | Dallas Mapped Gust | Representative Buildings |
|---|---|---|
| I · 300-yr map | ~100–105 mph | Minor agricultural, temporary and storage structures |
| II · 700-yr map | 105–115 mph | Homes, retail, offices and most standard occupancies |
| III · 1,700-yr map | ~120–130 mph | Schools, large assembly, substantial-hazard occupancies |
| IV · 3,000-yr map | ~130–140 mph | Hospitals, fire stations, shelters and emergency centers |
PERMIT PATHWAY
Clearing a wind-load review inside Dallas County
Texas has no statewide code, so Dallas builds on the IBC with state amendments. These are the six pieces a North Texas submittal turns on.
IBC + Texas amendments
Dallas adopts the International Building Code with TDLR state amendments referencing ASCE 7-22.
CODE BASISMapped basic wind speed
Pull V from the ASCE 7-22 map for the site: 105–115 mph for ordinary Dallas occupancies.
V = 105–115Exposure determination
Justify B for built-up sites or C for the open northern edge based on upwind terrain.
B OR CRisk category check
Confirm occupancy class so the correct return-period map and gust apply to the design.
TABLE 1.5-1City of Dallas review
Development Services permits work inside the city; the county inspects unincorporated tracts.
JURISDICTIONPE-sealed calculations
Commercial and complex Dallas projects need calcs sealed by a Texas-licensed Professional Engineer.
TEXAS PEOfficial Dallas references: City of Dallas Building Inspection · Dallas County Building Inspection · Texas PE Licensing Board (PELS)
INLAND VS GULF
Why a Dallas frame is not a Texas coast frame
The same state, two very different design problems. North Texas trades hurricane debris rules for tornado-grade base winds.
| Requirement | Dallas (Inland) | Texas Coast HVHZ |
|---|---|---|
| Design wind speed | 105–115 mph | 140–160 mph |
| Exposure category | Mostly B, some C in new areas | C required |
| TDI product evaluation | Not required | Required for TWIA |
| WPI-8 certification | Not required | Required for TWIA |
| Wind-borne debris | Not required | Impact protection required |
| Primary hazard | Tornadoes, severe thunderstorms | Hurricanes, tropical storms |
ACROSS THE METROPLEX
Carry these loads to the rest of North Texas
Wind speeds run consistent across DFW, but exposure shifts fast in the growth corridors. Branch out from Dallas to the wider state map.
Texas statewide requirements
The full Texas wind-load picture, from inland prairie to the Gulf coastline.
STATE HUBWind speed by location
Look up the mapped basic wind speed for any U.S. address or ZIP.
LOOKUPAll state requirements
Compare adopted codes and ASCE 7 editions across every U.S. state.
DIRECTORYFINISH THE DALLAS CALC
Turn the North Texas wind map into a sealed permit set
Enter a Dallas address and the calculator applies the 105–115 mph gust, sorts Exposure B or C, runs the risk category, and returns MWFRS and C&C pressures ready for review.