Also in: Disaster Response and Recovery
Wind Velocity Pressure
The wind pressure on a wall or roof at a design wind speed.
Example
You enter
- Basic wind speed (mph) 100
- Exposure C
You get
- Velocity pressure q 25.6 psf
- qz at 30 ft 25.09 psf
- Windward pressure 20.0704
- Leeward pressure -12.544
Checked against published worked examples from: ASCE.
Details, formula, and sources
Scopeq = 0.00256 * V^2 with windward and leeward Cp.
Formula or tableDesign velocity pressure q = 0.00256 × V² × Kz × Kzt × Kd (psf), with Kd folded into q as ASCE 7-16 wrote it; ASCE 7-22 writes qz = 0.00256 Kz Kzt Ke V² and applies Kd in the pressure equations, giving the same pressure. Ke (ground elevation) is taken as 1.0, which is conservative. V from the ASCE Hazard Tool.
Source and editionASCE 7-22 (Minimum Design Loads for Buildings and Other Structures). Section 26.10. Public formula; licensed text not reproduced. Basic wind speed V from the ASCE Hazard Tool for the site and risk category.
Free accessASCE 7 licensed; ASCE-7 hazard tool free at asce7hazardtool.online (per ASCE outreach). ATC Hazards by Location (hazards.atcouncil.org) also reports the ASCE 7 values.
What governsEstimate. AHJ and licensed structural engineer govern.
API field namesV_mph, exposure, q_psf, qz_at_30ft_psf, pressure_windward_psf, pressure_leeward_psf
- Air-density factor 0.00256 ASCE 7-22 Section 26.10ASCE 7-22 by name
- Exposure / Kz / Kzt / Kd / Ke user-supplied (data/construction/wind-snow-zones.json states the formula only; until 2026-10-17 this said the factors could come from it, which they could not)ASCE 7-22