Wind Load Calculator

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The 3-second gust design wind speed for the site. In the US, ASCE 7 risk-category maps give this value by location (commonly 85-170 mph for Risk Category II).
mph
ASCE 7 exposure category. Category B is suburban or wooded areas with closely spaced obstructions. Category C is open terrain with scattered obstructions under 30 ft. Category D is flat, unobstructed coastal or water-front areas.
Mean roof height of the structure. The Kz coefficient is interpolated at this height.
ft
The dimension of the building face that is directly exposed to the wind (the windward face).
ft
The dimension running in the direction of wind flow. Used to compute the L/B ratio for the leeward pressure coefficient.
ft
ASCE 7 permits G = 0.85 for rigid structures (natural frequency > 1 Hz). Flexible or dynamically sensitive structures require a calculated Gf, which may be higher.
Kd accounts for the reduced probability of the maximum wind speed occurring in the most critical direction. ASCE 7 Table 26.6-1: buildings = 0.85, solid signs = 0.85, open signs = 0.95.
ASCE 7 Risk Category. For wind, the importance factor (Ie) = 1.0 for Risk Category II. However, the risk category affects the design wind speed map used; use the appropriate map speed for your category.
Standard sea-level air density is 1.225 kg/m³. Reduce for high-altitude sites (e.g. Denver at 1600 m is about 1.045 kg/m³). The ASCE 7 imperial constant 0.00256 assumes standard sea-level air density.
kg/m³
Velocity pressure (qz)High wind demand
28.2psf

Basic velocity pressure at the building height, before pressure coefficients

Velocity pressure (qz)1,350.3Pa
Windward design pressure19.18psf
Leeward design pressure9.59psf
Net combined pressure28.77psf
Windward wall force23,013lbf
Total wind force (net)34,519lbf
Exposure coefficient (Kz)0.98
Windward pressure19.18
Leeward pressure (suction)9.59
Velocity pressure (qz)28.2
28.77 psf
Low<10Moderate10-25High25+

Net design wind pressure: 28.8 psf

  • The velocity pressure at the specified height is 28.20 psf, giving a net design pressure of 28.77 psf on the combined windward and leeward walls.
  • The exposure coefficient Kz = 0.980 for Exposure Category C at the given height. Higher terrain categories and greater heights both increase Kz, directly raising the design pressure.
  • The depth-to-width ratio (L/B) is 1.50, which sets the leeward pressure coefficient at -0.40. Deeper buildings relative to their width experience less leeward suction.
  • Total design wind force acting on the structure is 34,519 lbf. This must be resisted by the lateral force-resisting system (shear walls, moment frames, or bracing).

Next stepThese pressures are simplified design values. A licensed structural engineer should verify them and check component-and-cladding pressures, roof uplift, and overturning moment for final design.

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