ASCE 7-22 · CHAPTER 29 · SIGNS & BILLBOARDS
Wind Loads on Signs & Billboards
Large face area, elevated, fully exposed — signs catch wind like a sail. ASCE 7-22 Chapter 29 sets the force.
THE PICTURE
Wind pushes on the whole sign face
The full panel area As resists the flow; the resultant force acts at the centroid, well above the ground.
THE EQUATION
The sign force equation
F = qh · G · Cf · As
qh
Velocity pressure at sign height: 0.00256·KzKztKdKeV².
Kd = 0.85G
Gust-effect factor for a rigid sign structure.
G = 0.85Cf
Force coefficient from Fig 29.3-1 — set by aspect ratio and clearance to ground.
QUALITATIVEAs
Gross area of the sign face the wind acts on.
SIGN AREATWO FAMILIES
Solid signs vs open signs
How much wind a sign sheds depends on how much of its face is actually solid.
Solid signs
A full, closed face (billboards, monument and panel signs). The force coefficient applies to the entire area As — governed by Fig 29.3-1 for solid attached and freestanding signs.
FIG 29.3-1Open / lattice signs
Slats, frames, and see-through lattice. Wind passes between members, so the load is reduced by the solidity ratio — open signs and single-plane open frames follow Fig 29.4-2.
FIG 29.4-2DRIVERS
What actually moves the load
Four geometry factors feed qh, Cf, and As — change one and the force shifts.
Height
Taller centroids see a higher Kz, raising qh and the design force.
qhArea
Force scales directly with As — double the panel, double the load.
AsAspect ratio
Width-to-height shapes Cf in Fig 29.3-1 — long signs behave differently.
CfClearance to ground
The gap below the panel changes Cf; ground effect modifies how the flow loads the face.
CfRUN THE NUMBERS
Size your sign & billboard loads
Get the Chapter 29 force F = qhGCfAs for your panel, height, and exposure.
KEEP READING
Related guides
Specialty Structures Wind Loads
Chapter 29 loads on signs, walls, towers, and other structures.
CHAPTER 29Design Methods (ASCE 7)
How the directional procedures and load paths fit together.
METHODSWind Directionality Factor
What Kd = 0.85 means and why signs use it.
KdREFERENCES
- ASCE 7 Hazard Tool — site-specific wind speeds
- ASCE/SEI 7-22 Standard — official publication
- ICC Digital Codes — building code reference