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Wind Pressure

Velocity pressure is q_z = 0.613·K_z·K_zt·K_d·V² in SI. Because it goes as the square of speed, a 25% faster wind is 56% more pressure — which is why a small change in the mapped wind speed matters so much. This gives the velocity pressure; turning it into a force needs the pressure coefficients for your building shape.

Basic wind speed V (m/s)

Exposure coefficient Kz

Topographic factor Kzt

Directionality Kd

Pressure coefficient GCp

Tributary area (m²)

Velocity pressure qz

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qz in kPa

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Design pressure

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Force on the area

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If GCp were suction (−)

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qz at +25% wind speed

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Kz depends on height and exposure category, Kzt on terrain, and GCp on the building shape and the zone (corners and edges are far worse than the field of a wall). Take all of them from the code tables for your actual building — the defaults here are placeholders.

PRELIMINARY SIZING ONLY — not a code-compliant design check. These are first-pass equations; they omit member stability, local buckling, shear and combined-stress interaction, connections, second-order effects and jurisdiction-specific factors. Codes vary by country and edition. Structural design must be performed and sealed by a qualified engineer.