NORTH CAROLINA · WAKE COUNTY / CITY OF RALEIGH

Where the Research Triangle meets the Piedmont wind map

Raleigh sits roughly 140 miles inland from the Atlantic, yet weakened hurricanes still reach the capital. Here is how Wake County frames the wind load math.

110–120MPH RISK II · VARIES BY SITE

WakeCOUNTY / JURISDICTION

ASCE 7-22VIA NC STATE BUILDING CODE

Exp BURBAN PIEDMONT TERRAIN

PIEDMONT EXPOSURE

Why a landlocked capital still designs for tropical wind

Coastal storms lose their eye over land but not their gusts. Raleigh's range reflects four inland drivers, not a single hurricane track.

Weakened tropical systems

Fran (1996), Floyd (1999) and Florence (2018) reached Wake County after landfall, dragging tropical-storm-force gusts inland.

REMNANT WIND

Severe Piedmont thunderstorms

Spring and summer convection drives damaging straight-line winds across the Triangle on a near-annual basis.

STRAIGHT-LINE

Central-NC tornado outbreaks

The April 2011 outbreak carved damage paths through Wake County, a reminder that inland does not mean immune.

EF-RATED

Derecho-scale wind complexes

Organized storm clusters can spread a broad swath of damaging wind over the entire Research Triangle at once.

WIDE SWATH

SITE INPUTS · RALEIGH

The Triangle's terrain reads as Exposure B almost everywhere

Dense neighborhoods plus one of the country's broadest urban tree canopies push most Raleigh sites firmly into the suburban roughness category.

Canopy + dense build = B

Downtown, North Hills, RTP and established neighborhoods all satisfy Exposure B under ASCE 7 Section 26.7.

EXPOSURE B

Where C may apply

Large cleared parcels or the open ground around RDU International can warrant Exposure C on engineering judgment.

EDGE CASES

Rolling Piedmont ridges

Hilltop sites can lift the topographic factor Kzt above 1.0; flat lots stay at 1.0 per Section 26.8.

CHECK Kzt

Risk Category sets which map you read: a longer return period raises Raleigh's design wind speed. The actual mph still varies by site — never lock a single exact value without checking Wake County's adopted map.

PERMIT-READY CHECKLIST

What a Wake County submittal actually has to show

Six inputs decide whether your Raleigh wind calc clears review the first time.

Design wind speed V

110–120 mph for Risk II, read from the ASCE 7-22 map for your address.

RISK II

Exposure category

Default B across the metro; justify any C call against the surrounding terrain.

B / (C)

Topographic factor

Kzt = 1.0 on flat lots; evaluate ridges and crests per Section 26.8.

Kzt

Risk category

Schools, assembly and hospitals shift to a higher-speed map.

I–IV

C&C + MWFRS

Cladding and main-frame pressures both reported for the structure.

PRESSURES

NC PE seal

Commercial and complex work needs a North Carolina-licensed PE seal.

PE-READY

JURISDICTION + STATEWIDE

Verify with the offices that stamp the permit

Official Wake County and North Carolina sources, plus the statewide context for the Triangle.

RUN THE TRIANGLE NUMBERS

Drop in a Raleigh address and let the calculator size the wind

It pulls the Wake County V from the ASCE 7-22 map, sets Exposure B, and returns C&C and MWFRS pressures in a PE-ready report.

Calculate Raleigh wind loads North Carolina overview